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C# || Longest Valid Parentheses – How To Find The Longest Valid Well Formed Parentheses Using C#

May 24, 2022 admin No comments

The following is a module with functions which demonstrates how to find the longest valid well formed parentheses using C#.

1. Longest Valid Parentheses – Problem Statement

Given a string containing just the characters ‘(‘ and ‘)’, find the length of the longest valid (well-formed) parentheses substring.

Example 1:

Input: s = "(()" Output: 2 Explanation: The longest valid parentheses substring is "()".

Example 2:

Input: s = ")()())" Output: 4 Explanation: The longest valid parentheses substring is "()()".

Example 3:

Input: s = "" Output: 0

2. Longest Valid Parentheses – Solution

The following is a solution which demonstrates how to find the longest valid well formed parentheses.

In this solution we can make use of a stack while scanning the given string to:

Check if the string scanned so far is valid

Find the length of the longest valid string

In order to do so, we start by pushing -1 onto the stack. For every ‘(‘ encountered, we push its index onto the stack.

For every ‘)‘ encountered, we pop the topmost element. Then, the length of the currently encountered valid string of parentheses will be the difference between the current element’s index and the top element of the stack.

If, while popping the element, the stack becomes empty, we will push the current element’s index onto the stack. In this way, we can continue to calculate the length of the valid substrings and return the length of the longest valid string at the end.





		
		
			2. Longest Valid Parentheses - Solution
			
C#
			
			// ============================================================================
//    Author: Kenneth Perkins
//    Date:   May 24, 2022
//    Taken From: http://programmingnotes.org/
//    File:  Solution.cs
//    Description: Demonstrates how to find the longest valid parentheses
// ============================================================================
public class Solution {
    public int LongestValidParentheses(string s) {
        var result = 0;
        var stack = new Stack<int>();
        stack.Push(-1);
        for (var index = 0; index < s.Length; ++index) {
            if (s[index] == '(') {
                stack.Push(index);
            } else {
                stack.Pop();
                if (stack.Count == 0) {
                    stack.Push(index);
                } else {
                    result = Math.Max(result, index - stack.Peek());
                }
            }
        }
        return result;
    }
}// http://programmingnotes.org/
			
				
					
				
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						// ============================================================================
//    Author: Kenneth Perkins
//    Date:   May 24, 2022
//    Taken From: http://programmingnotes.org/
//    File:  Solution.cs
//    Description: Demonstrates how to find the longest valid parentheses
// ============================================================================
public class Solution {
    public int LongestValidParentheses(string s) {
        var result = 0;
        var stack = new Stack<int>();
        stack.Push(-1);
        for (var index = 0; index < s.Length; ++index) {
            if (s[index] == '(') {
                stack.Push(index);
            } else {
                stack.Pop();
                if (stack.Count == 0) {
                    stack.Push(index);
                } else {
                    result = Math.Max(result, index - stack.Peek());
                }
            }
        }
        return result;
    }
}// http://programmingnotes.org/

QUICK NOTES:
The highlighted lines are sections of interest to look out for.

The code is heavily commented, so no further insight is necessary. If you have any questions, feel free to leave a comment below.

Once compiled, you should get this as your output for the example cases:

2 4 0

C# || Backspace String Compare – How To Backspace Compare Two Strings Using C#

May 23, 2022 admin No comments

The following is a module with functions which demonstrates how to backspace compare two strings using C#.

1. Backspace Compare – Problem Statement

Given two strings s and t, return true if they are equal when both are typed into empty text editors. ‘#’ means a backspace character.

Note that after backspacing an empty text, the text will continue empty.

Example 1:

Input: s = "ab#c", t = "ad#c" Output: true Explanation: Both s and t become "ac".

Example 2:

Input: s = "ab##", t = "c#d#" Output: true Explanation: Both s and t become "".

Example 3:

Input: s = "a#c", t = "b" Output: false Explanation: s becomes "c" while t becomes "b".

2. Backspace Compare – Solution

The following is a solution which demonstrates how to backspace compare two strings.





		
		
			2. Backspace Compare - Solution
			
C#
			
			// ============================================================================
//    Author: Kenneth Perkins
//    Date:   May 23, 2022
//    Taken From: http://programmingnotes.org/
//    File:  Solution.cs
//    Description: Demonstrates how to backspace compare two strings
// ============================================================================
public class Solution {
    public bool BackspaceCompare(string s, string t) {
        return Clean(s) == Clean(t);
    }

    public string Clean(string source) {
        // Create result buffer
        var buffer = new StringBuilder();
        foreach (var ch in source) {
            if (ch == '#') {
                // Backspace by removing the last character in the buffer
                if (buffer.Length > 0) {
                    buffer.Length -= 1;
                }
            } else {
                // Add the character to the buffer
                buffer.Append(ch);
            }
        }
        return buffer.ToString();
    }
}// http://programmingnotes.org/
			
				
					
				
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						// ============================================================================
//    Author: Kenneth Perkins
//    Date:   May 23, 2022
//    Taken From: http://programmingnotes.org/
//    File:  Solution.cs
//    Description: Demonstrates how to backspace compare two strings
// ============================================================================
public class Solution {
    public bool BackspaceCompare(string s, string t) {
        return Clean(s) == Clean(t);
    }
 
    public string Clean(string source) {
        // Create result buffer
        var buffer = new StringBuilder();
        foreach (var ch in source) {
            if (ch == '#') {
                // Backspace by removing the last character in the buffer
                if (buffer.Length > 0) {
                    buffer.Length -= 1;
                }
            } else {
                // Add the character to the buffer
                buffer.Append(ch);
            }
        }
        return buffer.ToString();
    }
}// http://programmingnotes.org/

QUICK NOTES:
The highlighted lines are sections of interest to look out for.

The code is heavily commented, so no further insight is necessary. If you have any questions, feel free to leave a comment below.

Once compiled, you should get this as your output for the example cases:

true true false

C# || How To Design Underground System To Keep Track Of Customer Travel Times Between Stations Using C#

May 01, 2022 admin No comments

The following is a module with functions which demonstrates how to design an underground system to keep track of customer travel times between different stations using C#.

1. Underground System – Problem Statement

An underground railway system is keeping track of customer travel times between different stations. They are using this data to calculate the average time it takes to travel from one station to another.

Implement the UndergroundSystem class:

void checkIn(int id, string stationName, int t)
- A customer with a card ID equal to id, checks in at the station stationName at time t.
- A customer can only be checked into one place at a time.
void checkOut(int id, string stationName, int t)
- A customer with a card ID equal to id, checks out from the station stationName at time t.
double getAverageTime(string startStation, string endStation)
- Returns the average time it takes to travel from startStation to endStation.
- The average time is computed from all the previous traveling times from startStation to endStation that happened directly, meaning a check in at startStation followed by a check out from endStation.
- The time it takes to travel from startStation to endStation may be different from the time it takes to travel from endStation to startStation.
- There will be at least one customer that has traveled from startStation to endStation before getAverageTime is called.

You may assume all calls to the checkIn and checkOut methods are consistent. If a customer checks in at time t₁ then checks out at time t₂, then t₁ < t₂. All events happen in chronological order.

Example 1:

Input ["UndergroundSystem","checkIn","checkIn","checkIn","checkOut","checkOut","checkOut","getAverageTime","getAverageTime","checkIn","getAverageTime","checkOut","getAverageTime"] [[],[45,"Leyton",3],[32,"Paradise",8],[27,"Leyton",10],[45,"Waterloo",15],[27,"Waterloo",20],[32,"Cambridge",22],["Paradise","Cambridge"],["Leyton","Waterloo"],[10,"Leyton",24],["Leyton","Waterloo"],[10,"Waterloo",38],["Leyton","Waterloo"]]
Output [null,null,null,null,null,null,null,14.00000,11.00000,null,11.00000,null,12.00000]
Explanation UndergroundSystem undergroundSystem = new UndergroundSystem(); undergroundSystem.checkIn(45, "Leyton", 3); undergroundSystem.checkIn(32, "Paradise", 8); undergroundSystem.checkIn(27, "Leyton", 10); undergroundSystem.checkOut(45, "Waterloo", 15); // Customer 45 "Leyton" -> "Waterloo" in 15-3 = 12 undergroundSystem.checkOut(27, "Waterloo", 20); // Customer 27 "Leyton" -> "Waterloo" in 20-10 = 10 undergroundSystem.checkOut(32, "Cambridge", 22); // Customer 32 "Paradise" -> "Cambridge" in 22-8 = 14 undergroundSystem.getAverageTime("Paradise", "Cambridge"); // return 14.00000. One trip "Paradise" -> "Cambridge", (14) / 1 = 14 undergroundSystem.getAverageTime("Leyton", "Waterloo"); // return 11.00000. Two trips "Leyton" -> "Waterloo", (10 + 12) / 2 = 11 undergroundSystem.checkIn(10, "Leyton", 24); undergroundSystem.getAverageTime("Leyton", "Waterloo"); // return 11.00000 undergroundSystem.checkOut(10, "Waterloo", 38); // Customer 10 "Leyton" -> "Waterloo" in 38-24 = 14 undergroundSystem.getAverageTime("Leyton", "Waterloo"); // return 12.00000. Three trips "Leyton" -> "Waterloo", (10 + 12 + 14) / 3 = 12

Example 2:

Input ["UndergroundSystem","checkIn","checkOut","getAverageTime","checkIn","checkOut","getAverageTime","checkIn","checkOut","getAverageTime"] [[],[10,"Leyton",3],[10,"Paradise",8],["Leyton","Paradise"],[5,"Leyton",10],[5,"Paradise",16],["Leyton","Paradise"],[2,"Leyton",21],[2,"Paradise",30],["Leyton","Paradise"]]
Output [null,null,null,5.00000,null,null,5.50000,null,null,6.66667]
Explanation UndergroundSystem undergroundSystem = new UndergroundSystem(); undergroundSystem.checkIn(10, "Leyton", 3); undergroundSystem.checkOut(10, "Paradise", 8); // Customer 10 "Leyton" -> "Paradise" in 8-3 = 5 undergroundSystem.getAverageTime("Leyton", "Paradise"); // return 5.00000, (5) / 1 = 5 undergroundSystem.checkIn(5, "Leyton", 10); undergroundSystem.checkOut(5, "Paradise", 16); // Customer 5 "Leyton" -> "Paradise" in 16-10 = 6 undergroundSystem.getAverageTime("Leyton", "Paradise"); // return 5.50000, (5 + 6) / 2 = 5.5 undergroundSystem.checkIn(2, "Leyton", 21); undergroundSystem.checkOut(2, "Paradise", 30); // Customer 2 "Leyton" -> "Paradise" in 30-21 = 9 undergroundSystem.getAverageTime("Leyton", "Paradise"); // return 6.66667, (5 + 6 + 9) / 3 = 6.66667

2. Underground System – Solution

The following is a solution which demonstrates how to design an underground system to keep track of customer travel times between different stations.





		
		
			2. Underground System - Solution
			
C#
			
			// ============================================================================
//    Author: Kenneth Perkins
//    Date:   May 1, 2022
//    Taken From: http://programmingnotes.org/
//    File:  Solution.cs
//    Description: Demonstrates how to design underground system
// ============================================================================
public class UndergroundSystem {
    Dictionary<string, KeyValuePair<int, int>> checkoutMap;
    Dictionary<int, KeyValuePair<string, int>> checkInMap;

    public UndergroundSystem() {
        checkoutMap = new Dictionary<string, KeyValuePair<int, int>>(); // Route - {TotalTime, Count}
        checkInMap = new Dictionary<int, KeyValuePair<string, int>>();  // Uid - {StationName, Time}
    }

    public void CheckIn(int id, string stationName, int t) {
        checkInMap[id] = new KeyValuePair<string, int>(stationName, t);
    }

    public void CheckOut(int id, string stationName, int t) {
        var checkIn = checkInMap[id];
        var route = checkIn.Key + "_" + stationName;
        var totalTime = t - checkIn.Value;
        var checkout = checkoutMap.ContainsKey(route) ? checkoutMap[route] : new KeyValuePair<int, int>(0, 0);
        checkoutMap[route] = new KeyValuePair<int, int>(checkout.Key + totalTime, checkout.Value + 1);
    }

    public double GetAverageTime(string startStation, string endStation) {
        var route = startStation + "_" + endStation;
        var checkout = checkoutMap[route];
        return (double) checkout.Key / checkout.Value;
    }
}// http://programmingnotes.org/

/**
 * Your UndergroundSystem object will be instantiated and called as such:
 * UndergroundSystem obj = new UndergroundSystem();
 * obj.CheckIn(id,stationName,t);
 * obj.CheckOut(id,stationName,t);
 * double param_3 = obj.GetAverageTime(startStation,endStation);
 */
			
				
					
				
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						// ============================================================================
//    Author: Kenneth Perkins
//    Date:   May 1, 2022
//    Taken From: http://programmingnotes.org/
//    File:  Solution.cs
//    Description: Demonstrates how to design underground system
// ============================================================================
public class UndergroundSystem {
    Dictionary<string, KeyValuePair<int, int>> checkoutMap;
    Dictionary<int, KeyValuePair<string, int>> checkInMap;
 
    public UndergroundSystem() {
        checkoutMap = new Dictionary<string, KeyValuePair<int, int>>(); // Route - {TotalTime, Count}
        checkInMap = new Dictionary<int, KeyValuePair<string, int>>();  // Uid - {StationName, Time}
    }
 
    public void CheckIn(int id, string stationName, int t) {
        checkInMap[id] = new KeyValuePair<string, int>(stationName, t);
    }
 
    public void CheckOut(int id, string stationName, int t) {
        var checkIn = checkInMap[id];
        var route = checkIn.Key + "_" + stationName;
        var totalTime = t - checkIn.Value;
        var checkout = checkoutMap.ContainsKey(route) ? checkoutMap[route] : new KeyValuePair<int, int>(0, 0);
        checkoutMap[route] = new KeyValuePair<int, int>(checkout.Key + totalTime, checkout.Value + 1);
    }
 
    public double GetAverageTime(string startStation, string endStation) {
        var route = startStation + "_" + endStation;
        var checkout = checkoutMap[route];
        return (double) checkout.Key / checkout.Value;
    }
}// http://programmingnotes.org/
 
/**
 * Your UndergroundSystem object will be instantiated and called as such:
 * UndergroundSystem obj = new UndergroundSystem();
 * obj.CheckIn(id,stationName,t);
 * obj.CheckOut(id,stationName,t);
 * double param_3 = obj.GetAverageTime(startStation,endStation);
 */

QUICK NOTES:
The highlighted lines are sections of interest to look out for.

The code is heavily commented, so no further insight is necessary. If you have any questions, feel free to leave a comment below.

Once compiled, you should get this as your output for the example cases:

[null,null,null,null,null,null,null,14.00000,11.00000,null,11.00000,null,12.00000] [null,null,null,5.00000,null,null,5.50000,null,null,6.66667]

C# || Remove Linked List Elements – How To Remove All Target Linked List Elements Using C#

April 02, 2022 admin No comments

The following is a module with functions which demonstrates how to remove all target linked list elements using C#.

1. Remove Elements – Problem Statement

Given the head of a linked list and an integer val, remove all the nodes of the linked list that has Node.val == val, and return the new head.

Example 1:

Input: head = [1,2,6,3,4,5,6], val = 6 Output: [1,2,3,4,5]

Example 2:

Input: head = [], val = 1 Output: []

Example 3:

Input: head = [7,7,7,7], val = 7 Output: []

2. Remove Elements – Solution

The following is a solution which demonstrates how to remove all target linked list elements.





		
		
			2. Remove Elements - Solution
			
C#
			
			// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Apr 2, 2022
//    Taken From: http://programmingnotes.org/
//    File:  Solution.cs
//    Description: Demonstrates how to remove all target linked list elements
// ============================================================================
/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     public int val;
 *     public ListNode next;
 *     public ListNode(int val=0, ListNode next=null) {
 *         this.val = val;
 *         this.next = next;
 *     }
 * }
 */
public class Solution {
    public ListNode RemoveElements(ListNode head, int val) {
        var ptr = head;

        // Loop through data checking to see if the next node equals the target value
        while (ptr != null && ptr.next != null) {

            // If the next node value is the target value, set the next node
            // to point to the one after it
            if (ptr.next.val == val) {
                ptr.next = ptr.next.next;
            } else {
                // Advance to the next node
                ptr = ptr.next;
            }
        }

        // If the head equals the target value, advance to the next
        if (head != null && head.val == val) {
            head = head.next;
        }

        return head;
    }
}// http://programmingnotes.org/
			
				
					
				
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						// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Apr 2, 2022
//    Taken From: http://programmingnotes.org/
//    File:  Solution.cs
//    Description: Demonstrates how to remove all target linked list elements
// ============================================================================
/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     public int val;
 *     public ListNode next;
 *     public ListNode(int val=0, ListNode next=null) {
 *         this.val = val;
 *         this.next = next;
 *     }
 * }
 */
public class Solution {
    public ListNode RemoveElements(ListNode head, int val) {
        var ptr = head;
 
        // Loop through data checking to see if the next node equals the target value
        while (ptr != null && ptr.next != null) {
 
            // If the next node value is the target value, set the next node
            // to point to the one after it
            if (ptr.next.val == val) {
                ptr.next = ptr.next.next;
            } else {
                // Advance to the next node
                ptr = ptr.next;
            }
        }
 
        // If the head equals the target value, advance to the next
        if (head != null && head.val == val) {
            head = head.next;
        }
 
        return head;
    }
}// http://programmingnotes.org/

QUICK NOTES:
The highlighted lines are sections of interest to look out for.

The code is heavily commented, so no further insight is necessary. If you have any questions, feel free to leave a comment below.

Once compiled, you should get this as your output for the example cases:

[1,2,3,4,5] [] []

C# || How To Compare Version Numbers Using C#

March 01, 2022 admin No comments

The following is a module with functions which demonstrates how to compare version numbers using C#.

1. Compare Version – Problem Statement

Given two version numbers, version1 and version2, compare them.

Version numbers consist of one or more revisions joined by a dot ‘.’. Each revision consists of digits and may contain leading zeros. Every revision contains at least one character. Revisions are 0-indexed from left to right, with the leftmost revision being revision 0, the next revision being revision 1, and so on. For example 2.5.33 and 0.1 are valid version numbers.

To compare version numbers, compare their revisions in left-to-right order. Revisions are compared using their integer value ignoring any leading zeros. This means that revisions 1 and 001 are considered equal. If a version number does not specify a revision at an index, then treat the revision as 0. For example, version 1.0 is less than version 1.1 because their revision 0s are the same, but their revision 1s are 0 and 1 respectively, and 0 < 1.

Return the following:

If version1 < version2, return -1.
If version1 > version2, return 1.
Otherwise, return 0.

Example 1:

Input: version1 = "1.01", version2 = "1.001" Output: 0 Explanation: Ignoring leading zeroes, both "01" and "001" represent the same integer "1".

Example 2:

Input: version1 = "1.0", version2 = "1.0.0" Output: 0 Explanation: version1 does not specify revision 2, which means it is treated as "0".

Example 3:

Input: version1 = "0.1", version2 = "1.1" Output: -1 Explanation: version1's revision 0 is "0", while version2's revision 0 is "1". 0 < 1, so version1 < version2.

2. Compare Version – Solution

The following is a solution which demonstrates how to compare version numbers.





		
		
			2. Compare Version - Solution
			
C#
			
			// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Mar 1, 2022
//    Taken From: http://programmingnotes.org/
//    File:  Solution.cs
//    Description: Demonstrates how to compare version numbers
// ============================================================================
public class Solution {
    public int CompareVersion(string version1, string version2) {
        var revisions1 = version1.Split(".");
        var revisions2 = version2.Split(".");

        var length = Math.Max(revisions1.Length, revisions2.Length);
        for (int index = 0; index < length; ++index) {
            var v1 = index < revisions1.Length ? int.Parse(revisions1[index]) : 0;
            var v2 = index < revisions2.Length ? int.Parse(revisions2[index]) : 0;
            if (v1 < v2) {
                return -1;
            } else if (v1 > v2) {
                return 1;
            }
        }
        return 0;
    }
}// http://programmingnotes.org/
			
				
					
				
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						// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Mar 1, 2022
//    Taken From: http://programmingnotes.org/
//    File:  Solution.cs
//    Description: Demonstrates how to compare version numbers
// ============================================================================
public class Solution {
    public int CompareVersion(string version1, string version2) {
        var revisions1 = version1.Split(".");
        var revisions2 = version2.Split(".");
 
        var length = Math.Max(revisions1.Length, revisions2.Length);
        for (int index = 0; index < length; ++index) {
            var v1 = index < revisions1.Length ? int.Parse(revisions1[index]) : 0;
            var v2 = index < revisions2.Length ? int.Parse(revisions2[index]) : 0;
            if (v1 < v2) {
                return -1;
            } else if (v1 > v2) {
                return 1;
            }
        }
        return 0;
    }
}// http://programmingnotes.org/

QUICK NOTES:
The highlighted lines are sections of interest to look out for.

The code is heavily commented, so no further insight is necessary. If you have any questions, feel free to leave a comment below.

Once compiled, you should get this as your output for the example cases:

0 0 -1

C# || How To Find The Difference Between Two Strings Using C#

February 06, 2022 admin No comments

The following is a module with functions which demonstrates how to find the difference between two strings using C#.

1. Find The Difference – Problem Statement

You are given two strings s and t.

String t is generated by random shuffling string s and then add one more letter at a random position.

Return the letter that was added to t.

Example 1:

Input: s = "abcd", t = "abcde" Output: "e" Explanation: 'e' is the letter that was added.

Example 2:

Input: s = "", t = "y" Output: "y"

2. Find The Difference – Solution

The following is a solution which demonstrates how to find the difference between two strings.





		
		
			2. Find The Difference - Solution
			
C#
			
			// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Feb 6, 2022
//    Taken From: http://programmingnotes.org/
//    File:  Solution.cs
//    Description: Demonstrates how to find the difference between two strings
// ============================================================================
public class Solution {
    public char FindTheDifference(string s, string t) {
        var result = ' ';

        // Create a map with the frequency each character has been seen from the first string
        var seen = new Dictionary<char, int>();
        foreach (var letter in s) {
            seen[letter] = (seen.ContainsKey(letter) ? seen[letter] : 0) + 1;
        }

        // Decrease the frequency of the characters we've seen from the second string
        foreach (var letter in t) {
            // Either we havent seen this character, or its frequency has reached 0
            if (!seen.ContainsKey(letter) || seen[letter] == 0) {
                result = letter;
                break;
            }

            // Decrease the frequency
            --seen[letter];
        }

        return result;
    }
}// http://programmingnotes.org/
			
				
					
				
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						// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Feb 6, 2022
//    Taken From: http://programmingnotes.org/
//    File:  Solution.cs
//    Description: Demonstrates how to find the difference between two strings
// ============================================================================
public class Solution {
    public char FindTheDifference(string s, string t) {
        var result = ' ';
 
        // Create a map with the frequency each character has been seen from the first string
        var seen = new Dictionary<char, int>();
        foreach (var letter in s) {
            seen[letter] = (seen.ContainsKey(letter) ? seen[letter] : 0) + 1;
        }
 
        // Decrease the frequency of the characters we've seen from the second string
        foreach (var letter in t) {
            // Either we havent seen this character, or its frequency has reached 0
            if (!seen.ContainsKey(letter) || seen[letter] == 0) {
                result = letter;
                break;
            }
 
            // Decrease the frequency
            --seen[letter];
        }
 
        return result;
    }
}// http://programmingnotes.org/

QUICK NOTES:
The highlighted lines are sections of interest to look out for.

The code is heavily commented, so no further insight is necessary. If you have any questions, feel free to leave a comment below.

Once compiled, you should get this as your output for the example cases:

"e" "y"

C# || How To Get Total Sum Root To Leaf Binary Numbers In Binary Tree Using C#

January 10, 2022 admin No comments

The following is a module with functions which demonstrates how to get the total sum root to leaf binary numbers in a binary tree using C#.

1. Sum Root To Leaf – Problem Statement

You are given the root of a binary tree where each node has a value 0 or 1. Each root-to-leaf path represents a binary number starting with the most significant bit.

For example, if the path is 0 -> 1 -> 1 -> 0 -> 1, then this could represent 01101 in binary, which is 13.

For all leaves in the tree, consider the numbers represented by the path from the root to that leaf. Return the sum of these numbers.

The test cases are generated so that the answer fits in a 32-bits integer.

A leaf node is a node with no children.

Example 1:

Input: root = [1,0,1,0,1,0,1] Output: 22 Explanation: (100) + (101) + (110) + (111) = 4 + 5 + 6 + 7 = 22

Example 2:

Input: root = [0] Output: 0

2. Sum Root To Leaf – Solution

The following is a solution which demonstrates how to get the total sum root to leaf binary numbers in a binary tree.

This solution uses Depth First Search to explore items at each level.





		
		
			2. Sum Root To Leaf - Solution
			
C#
			
			// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Jan 10, 2022
//    Taken From: http://programmingnotes.org/
//    File:  Solution.cs
//    Description: Demonstrates how to get sum root to leaf binary numbers
// ============================================================================
/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     public int val;
 *     public TreeNode left;
 *     public TreeNode right;
 *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
public class Solution {
    public int SumRootToLeaf(TreeNode root) {
        return Traverse(root, 0);
    }
    private int Traverse(TreeNode node, int currentSum) {
        if (node == null) {
            return 0;
        }
        // Calculate current sum
        currentSum = (currentSum * 2) + node.val;

        // We have reached a leaf node
        if (node.left == null && node.right == null) {
            return currentSum;
        }
        // Keep traversing left and right calculating the sum
        return Traverse(node.left, currentSum) + Traverse(node.right, currentSum);
    }
}// http://programmingnotes.org/
			
				
					
				
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						// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Jan 10, 2022
//    Taken From: http://programmingnotes.org/
//    File:  Solution.cs
//    Description: Demonstrates how to get sum root to leaf binary numbers
// ============================================================================
/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     public int val;
 *     public TreeNode left;
 *     public TreeNode right;
 *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
public class Solution {
    public int SumRootToLeaf(TreeNode root) {
        return Traverse(root, 0);
    }
    private int Traverse(TreeNode node, int currentSum) {
        if (node == null) {
            return 0;
        }
        // Calculate current sum
        currentSum = (currentSum * 2) + node.val;
 
        // We have reached a leaf node
        if (node.left == null && node.right == null) {
            return currentSum;
        }
        // Keep traversing left and right calculating the sum
        return Traverse(node.left, currentSum) + Traverse(node.right, currentSum);
    }
}// http://programmingnotes.org/

QUICK NOTES:
The highlighted lines are sections of interest to look out for.

The code is heavily commented, so no further insight is necessary. If you have any questions, feel free to leave a comment below.

Once compiled, you should get this as your output for the example cases:

22 0

C# || Jump Game III – How To Check If You Can Reach Target Value In Array Using C#

December 08, 2021 admin No comments

The following is a module with functions which demonstrates how to check if you can reach a target value in an array using C#.

1. Can Reach – Problem Statement

Given an array of non-negative integers arr, you are initially positioned at start index of the array. When you are at index i, you can jump to i + arr[i] or i – arr[i], check if you can reach to any index with value 0.

Notice that you can not jump outside of the array at any time.

Example 1:

Input: arr = [4,2,3,0,3,1,2], start = 5 Output: true Explanation: All possible ways to reach at index 3 with value 0 are: index 5 -> index 4 -> index 1 -> index 3 index 5 -> index 6 -> index 4 -> index 1 -> index 3

Example 2:

Input: arr = [4,2,3,0,3,1,2], start = 0 Output: true Explanation: One possible way to reach at index 3 with value 0 is: index 0 -> index 4 -> index 1 -> index 3

Example 3:

Input: arr = [3,0,2,1,2], start = 2 Output: false Explanation: There is no way to reach at index 1 with value 0.

2. Can Reach – Solution

The following are two solutions which demonstrates how to check if you can reach a target value in an array.

The following solution uses Depth First Search when looking for the target value.





		
		
			2. Can Reach - DFS - Solution
			
C#
			
			// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Dec 8, 2021
//    Taken From: http://programmingnotes.org/
//    File:  Solution.cs
//    Description: Determines if a target value can be reached in an array
// ============================================================================
public class Solution {
    public bool CanReach(int[] arr, int start) {
        var visited = new bool[arr.Length];
        return DFS(arr, start, visited);
    }
    public bool DFS(int[] arr, int currentIndex, bool[] visited) {
        // Make sure parameters are in bounds
        if (currentIndex < 0 || currentIndex >= arr.Length) {
            return false;
        }
        // Check to see if the index has been visited
        if (visited[currentIndex]) {
            return false;
        }
        // Check to see if we found the target value
        if (arr[currentIndex] == 0) {
            return true;
        }
        // Mark current index as visited
        visited[currentIndex] = true;

        // Keep searching forwards and backwards
        var forwards = currentIndex + arr[currentIndex];
        var backwards = currentIndex - arr[currentIndex];

        return DFS(arr, backwards, visited) || DFS(arr, forwards, visited);
    }
}// http://programmingnotes.org/
			
				
					
				
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						// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Dec 8, 2021
//    Taken From: http://programmingnotes.org/
//    File:  Solution.cs
//    Description: Determines if a target value can be reached in an array
// ============================================================================
public class Solution {
    public bool CanReach(int[] arr, int start) {
        var visited = new bool[arr.Length];
        return DFS(arr, start, visited);
    }
    public bool DFS(int[] arr, int currentIndex, bool[] visited) {
        // Make sure parameters are in bounds
        if (currentIndex < 0 || currentIndex >= arr.Length) {
            return false;
        }
        // Check to see if the index has been visited
        if (visited[currentIndex]) {
            return false;
        }
        // Check to see if we found the target value
        if (arr[currentIndex] == 0) {
            return true;
        }
        // Mark current index as visited
        visited[currentIndex] = true;
 
        // Keep searching forwards and backwards
        var forwards = currentIndex + arr[currentIndex];
        var backwards = currentIndex - arr[currentIndex];
 
        return DFS(arr, backwards, visited) || DFS(arr, forwards, visited);
    }
}// http://programmingnotes.org/

The following solution uses Breadth First Search when looking for the target value.





		
		
			2. Can Reach - BFS - Solution
			
C#
			
			// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Dec 8, 2021
//    Taken From: http://programmingnotes.org/
//    File:  Solution.cs
//    Description: Determines if a target value can be reached in an array
// ============================================================================
public class Solution {
    public bool CanReach(int[] arr, int start) {
        var visited = new bool[arr.Length];
        var queue = new Queue<int>();

        queue.Enqueue(start);

        while (queue.Count > 0) {
            var currentIndex = queue.Dequeue();

            // Check to see if we found the target value
            if (arr[currentIndex] == 0) {
                return true;
            }
            // Mark current index as visited
            visited[currentIndex] = true;

            // Keep searching forwards and backwards
            var forwards = currentIndex + arr[currentIndex];
            var backwards = currentIndex - arr[currentIndex];
            var directions = new List<int>{forwards, backwards};

            foreach (var direction in directions) {
                if (direction >= 0 && direction < arr.Length && !visited[direction]) {
                    queue.Enqueue(direction);
                }
            }
        }
        return false;
    }
}// http://programmingnotes.org/
			
				
					
				
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						// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Dec 8, 2021
//    Taken From: http://programmingnotes.org/
//    File:  Solution.cs
//    Description: Determines if a target value can be reached in an array
// ============================================================================
public class Solution {
    public bool CanReach(int[] arr, int start) {
        var visited = new bool[arr.Length];
        var queue = new Queue<int>();
 
        queue.Enqueue(start);
 
        while (queue.Count > 0) {
            var currentIndex = queue.Dequeue();
 
            // Check to see if we found the target value
            if (arr[currentIndex] == 0) {
                return true;
            }
            // Mark current index as visited
            visited[currentIndex] = true;
 
            // Keep searching forwards and backwards
            var forwards = currentIndex + arr[currentIndex];
            var backwards = currentIndex - arr[currentIndex];
            var directions = new List<int>{forwards, backwards};
 
            foreach (var direction in directions) {
                if (direction >= 0 && direction < arr.Length && !visited[direction]) {
                    queue.Enqueue(direction);
                }
            }
        }
        return false;
    }
}// http://programmingnotes.org/

QUICK NOTES:
The highlighted lines are sections of interest to look out for.

The code is heavily commented, so no further insight is necessary. If you have any questions, feel free to leave a comment below.

Once compiled, you should get this as your output for the example cases:

true true false

C# || Maximum Product Subarray – How To Find Largest Product In Contiguous Subarray Using C#

December 02, 2021 admin No comments

The following is a module with functions which demonstrates how to find the largest product in a contiguous subarray using C#.

1. Max Product – Problem Statement

Given an integer array nums, find a contiguous non-empty subarray within the array that has the largest product, and return the product.

It is guaranteed that the answer will fit in a 32-bit integer.

A subarray is a contiguous subsequence of the array.

Example 1:

Input: nums = [2,3,-2,4] Output: 6 Explanation: [2,3] has the largest product 6.

Example 2:

Input: nums = [-2,0,-1] Output: 0 Explanation: The result cannot be 2, because [-2,-1] is not a subarray.

2. Max Product – Solution

The following is a solution which demonstrates how to find the largest product in a contiguous subarray.

This solution is inspired by Kadane’s algorithm to find the result.

The idea here is similar to the ‘Maximum Subarray‘ problem.

In this solution, we have two values:

The current cumulative maximum product up to current element The current cumulative minimum product up to current element

Each loop iteration, these values are updated by either multiplying the new element at the current index with the existing product, or starting fresh from current index.

When a negative number is encountered, the current max and current min values are swapped, because multiplying a negative number makes a big number smaller, and multiplying a negative number makes small number bigger. So their intent is redefined by swapping.





		
		
			2. Max Product - Solution
			
C#
			
			// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Dec 2, 2021
//    Taken From: http://programmingnotes.org/
//    File:  Solution.cs
//    Description: Demonstrates how to find maximum product contiguous subarray
// ============================================================================
public class Solution {
    public int MaxProduct(int[] nums) {
        // Store the result
        var result = nums[0];

        // The current maximum and minimum product of the subarray
        var currentMin = nums[0];
        var currentMax = nums[0];

        for (int index = 1; index < nums.Length; ++index) {
            // Swap current max/min because multiplying
            // a negative number makes a big number smaller,
            // and multiplying a negative number makes small number bigger.
            // So their intent is redefined by swapping
            if (nums[index] < 0) {
                var temp = currentMax;
                currentMax = currentMin;
                currentMin = temp;
            }

            // Determine the max/min product for the current number.
            // It is either the current number itself
            // or the max/min by the previous values times the current one
            currentMax = Math.Max(nums[index], currentMax * nums[index]);
            currentMin = Math.Min(nums[index], currentMin * nums[index]);

            // Keep track of the current max result
            result = Math.Max(result, currentMax);
        }
        return result;
    }
}// http://programmingnotes.org/
			
				
					
				
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						// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Dec 2, 2021
//    Taken From: http://programmingnotes.org/
//    File:  Solution.cs
//    Description: Demonstrates how to find maximum product contiguous subarray
// ============================================================================
public class Solution {
    public int MaxProduct(int[] nums) {
        // Store the result
        var result = nums[0];
 
        // The current maximum and minimum product of the subarray
        var currentMin = nums[0];
        var currentMax = nums[0];
 
        for (int index = 1; index < nums.Length; ++index) {
            // Swap current max/min because multiplying
            // a negative number makes a big number smaller,
            // and multiplying a negative number makes small number bigger.
            // So their intent is redefined by swapping
            if (nums[index] < 0) {
                var temp = currentMax;
                currentMax = currentMin;
                currentMin = temp;
            }
 
            // Determine the max/min product for the current number.
            // It is either the current number itself
            // or the max/min by the previous values times the current one
            currentMax = Math.Max(nums[index], currentMax * nums[index]);
            currentMin = Math.Min(nums[index], currentMin * nums[index]);
 
            // Keep track of the current max result
            result = Math.Max(result, currentMax);
        }
        return result;
    }
}// http://programmingnotes.org/

QUICK NOTES:
The highlighted lines are sections of interest to look out for.

The code is heavily commented, so no further insight is necessary. If you have any questions, feel free to leave a comment below.

Once compiled, you should get this as your output for the example cases:

6 0

C# || Maximum Subarray – How To Find Largest Sum In Contiguous Subarray Using C#

December 02, 2021 admin No comments

The following is a module with functions which demonstrates how to find the largest sum in a contiguous subarray using C#.

1. Max Sub Array – Problem Statement

Given an integer array nums, find the contiguous subarray (containing at least one number) which has the largest sum and return its sum.

A subarray is a contiguous part of an array.

Example 1:

Input: nums = [-2,1,-3,4,-1,2,1,-5,4] Output: 6 Explanation: [4,-1,2,1] has the largest sum = 6.

Example 2:

Input: nums = [1] Output: 1

Example 3:

Input: nums = [5,4,-1,7,8] Output: 23

2. Max Sub Array – Solution

The following is a solution which demonstrates how to find the largest sum in a contiguous subarray.

This solution uses Kadane’s algorithm to find the result.





		
		
			2. Max Sub Array - Solution
			
C#
			
			// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Dec 2, 2021
//    Taken From: http://programmingnotes.org/
//    File:  Solution.cs
//    Description: Demonstrates how to find maximum sum in contiguous subarray
// ============================================================================
public class Solution {
    public int MaxSubArray(int[] nums) {
        var result = nums[0];
        var current = result;

        for (int index = 1; index < nums.Length; ++index) {
            current = Math.Max(nums[index], nums[index] + current);
            result = Math.Max(result, current);
        }

        return result;
    }
}// http://programmingnotes.org/
			
				
					
				
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						// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Dec 2, 2021
//    Taken From: http://programmingnotes.org/
//    File:  Solution.cs
//    Description: Demonstrates how to find maximum sum in contiguous subarray
// ============================================================================
public class Solution {
    public int MaxSubArray(int[] nums) {
        var result = nums[0];
        var current = result;
 
        for (int index = 1; index < nums.Length; ++index) {
            current = Math.Max(nums[index], nums[index] + current);
            result = Math.Max(result, current);
        }
 
        return result;
    }
}// http://programmingnotes.org/

QUICK NOTES:
The highlighted lines are sections of interest to look out for.

The code is heavily commented, so no further insight is necessary. If you have any questions, feel free to leave a comment below.

Once compiled, you should get this as your output for the example cases:

6 1 23

C# || String To Integer (atoi) – How To Convert String To Signed Integer Using C#

November 30, 2021 admin 1 Comment

The following is a module with functions which demonstrates how to convert a string to 32-bit signed integer using C#.

1. My Atoi – Problem Statement

Implement the myAtoi(string s) function, which converts a string to a 32-bit signed integer (similar to C/C++’s atoi function).

The algorithm for myAtoi(string s) is as follows:

Read in and ignore any leading whitespace.
Check if the next character (if not already at the end of the string) is ‘-‘ or ‘+’. Read this character in if it is either. This determines if the final result is negative or positive respectively. Assume the result is positive if neither is present.
Read in next the characters until the next non-digit character or the end of the input is reached. The rest of the string is ignored.
Convert these digits into an integer (i.e. “123” -> 123, “0032” -> 32). If no digits were read, then the integer is 0. Change the sign as necessary (from step 2).
If the integer is out of the 32-bit signed integer range [-2³¹, 2³¹ – 1], then clamp the integer so that it remains in the range. Specifically, integers less than -2³¹ should be clamped to -2³¹, and integers greater than 2³¹ – 1 should be clamped to 2³¹ – 1.
Return the integer as the final result.

Note:

Only the space character ‘ ‘ is considered a whitespace character.
Do not ignore any characters other than the leading whitespace or the rest of the string after the digits.

Example 1:

Input: s = "42" Output: 42 Explanation: The underlined characters are what is read in, the caret is the current reader position. Step 1: "42" (no characters read because there is no leading whitespace) ^ Step 2: "42" (no characters read because there is neither a '-' nor '+') ^ Step 3: "42" ("42" is read in) ^ The parsed integer is 42. Since 42 is in the range [-2³¹, 2³¹ - 1], the final result is 42.

Example 2:

Input: s = " -42" Output: -42 Explanation: Step 1: " -42" (leading whitespace is read and ignored) ^ Step 2: " -42" ('-' is read, so the result should be negative) ^ Step 3: " -42" ("42" is read in) ^ The parsed integer is -42. Since -42 is in the range [-2³¹, 2³¹ - 1], the final result is -42.

Example 3:

Input: s = "4193 with words" Output: 4193 Explanation: Step 1: "4193 with words" (no characters read because there is no leading whitespace) ^ Step 2: "4193 with words" (no characters read because there is neither a '-' nor '+') ^ Step 3: "4193 with words" ("4193" is read in; reading stops because the next character is a non-digit) ^ The parsed integer is 4193. Since 4193 is in the range [-2³¹, 2³¹ - 1], the final result is 4193.

Example 4:

Input: s = "words and 987" Output: 0 Explanation: Step 1: "words and 987" (no characters read because there is no leading whitespace) ^ Step 2: "words and 987" (no characters read because there is neither a '-' nor '+') ^ Step 3: "words and 987" (reading stops immediately because there is a non-digit 'w') ^ The parsed integer is 0 because no digits were read. Since 0 is in the range [-2³¹, 2³¹ - 1], the final result is 0.

Example 5:

Input: s = "-91283472332" Output: -2147483648 Explanation: Step 1: "-91283472332" (no characters read because there is no leading whitespace) ^ Step 2: "-91283472332" ('-' is read, so the result should be negative) ^ Step 3: "-91283472332" ("91283472332" is read in) ^ The parsed integer is -91283472332. Since -91283472332 is less than the lower bound of the range [-2³¹, 2³¹ - 1], the final result is clamped to -2³¹ = -2147483648.

2. My Atoi – Solution

The following is a solution which demonstrates how to convert a string to 32-bit signed integer.





		
		
			2. My Atoi - Solution
			
C#
			
			// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Nov 30, 2021
//    Taken From: http://programmingnotes.org/
//    File:  Solution.cs
//    Description: Demonstrates how to convert string to integer
// ============================================================================
public class Solution {
    public int MyAtoi(string s) {
        // 1. Advance leading whitespace
        var index = 0;
        while (index < s.Length && char.IsWhiteSpace(s[index])) {
            ++index;
        }

        // 2. Determine if number is positive or negative
        var sign = 1;
        if (index < s.Length && (s[index] == '-' || s[index] == '+')) {
            if (s[index] == '-') {
                sign = -1;
            }
            ++index;
        }

        // 3. Convert char digits to numeric value
        var result = 0;
        while (index < s.Length && char.IsDigit(s[index])) {
            var digit = CharToInt(s[index]);
            // Check for overflow
            if (result > (int.MaxValue - digit) / 10) {
                return sign == -1 ? int.MinValue : int.MaxValue;
            }
            result = (result * 10) + digit;
            ++index;
        }
        return result * sign;
    }

    private static int CharToInt(char ch) {
        return ch - '0';
    }
}// http://programmingnotes.org/
			
				
					
				
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						// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Nov 30, 2021
//    Taken From: http://programmingnotes.org/
//    File:  Solution.cs
//    Description: Demonstrates how to convert string to integer
// ============================================================================
public class Solution {
    public int MyAtoi(string s) {
        // 1. Advance leading whitespace
        var index = 0;
        while (index < s.Length && char.IsWhiteSpace(s[index])) {
            ++index;
        }
 
        // 2. Determine if number is positive or negative
        var sign = 1;
        if (index < s.Length && (s[index] == '-' || s[index] == '+')) {
            if (s[index] == '-') {
                sign = -1;
            }
            ++index;
        }
 
        // 3. Convert char digits to numeric value
        var result = 0;
        while (index < s.Length && char.IsDigit(s[index])) {
            var digit = CharToInt(s[index]);
            // Check for overflow
            if (result > (int.MaxValue - digit) / 10) {
                return sign == -1 ? int.MinValue : int.MaxValue;
            }
            result = (result * 10) + digit;
            ++index;
        }
        return result * sign;
    }
 
    private static int CharToInt(char ch) {
        return ch - '0';
    }
}// http://programmingnotes.org/

QUICK NOTES:
The highlighted lines are sections of interest to look out for.

The code is heavily commented, so no further insight is necessary. If you have any questions, feel free to leave a comment below.

Once compiled, you should get this as your output for the example cases:

42 -42 4193 0 -2147483648

C# || Maximal Rectangle – How To Find Largest Rectangle Area Using C#

November 30, 2021 admin No comments

The following is a module with functions which demonstrates how to find the largest rectangle area containing only 1’s using C#.

1. Maximal Rectangle – Problem Statement

Given a rows x cols binary matrix filled with 0‘s and 1‘s, find the largest rectangle containing only 1‘s and return its area.

Example 1:

Input: matrix = [["1","0","1","0","0"],["1","0","1","1","1"],["1","1","1","1","1"],["1","0","0","1","0"]] Output: 6 Explanation: The maximal rectangle is shown in the above picture.

Example 2:

Input: matrix = [] Output: 0

Example 3:

Input: matrix = [["0"]] Output: 0

Example 4:

Input: matrix = [["1"]] Output: 1

Example 5:

Input: matrix = [["0","0"]] Output: 0

2. Maximal Rectangle – Solution

The following is a solution which demonstrates how to find the largest rectangle area containing only 1’s.

This solution uses the monotonic stack approach.





		
		
			2. Maximal Rectangle - Solution
			
C#
			
			// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Nov 30, 2021
//    Taken From: http://programmingnotes.org/
//    File:  Solution.cs
//    Description: Demonstrates how to find the largest rectangle area
// ============================================================================
public class Solution {
    public int MaximalRectangle(char[][] matrix) {
        if (matrix.Length == 0) {
            return 0;
        }

        var result = 0;
        var histogram = new int[matrix[0].Length + 1];
        for (int row = 0; row < matrix.Length; ++row) {
            var stack = new Stack<int>();
            for (int col = 0; col <= matrix[row].Length; ++col) {
                // Set value
                if (col < matrix[row].Length) {
                    if (matrix[row][col] == '1') {
                        histogram[col] += 1;
                    } else {
                        histogram[col] = 0;
                    }
                }

                // Compute area
                while (stack.Count > 0 && histogram[stack.Peek()] >= histogram[col]) {
                    var area = histogram[stack.Pop()] * (stack.Count == 0 ? col : (col - stack.Peek() - 1));
                    result = Math.Max(result, area);
                }
                stack.Push(col);
            }
        }
        return result;
    }
}// http://programmingnotes.org/
			
				
					
				
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						// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Nov 30, 2021
//    Taken From: http://programmingnotes.org/
//    File:  Solution.cs
//    Description: Demonstrates how to find the largest rectangle area
// ============================================================================
public class Solution {
    public int MaximalRectangle(char[][] matrix) {
        if (matrix.Length == 0) {
            return 0;
        }
 
        var result = 0;
        var histogram = new int[matrix[0].Length + 1];
        for (int row = 0; row < matrix.Length; ++row) {
            var stack = new Stack<int>();
            for (int col = 0; col <= matrix[row].Length; ++col) {
                // Set value
                if (col < matrix[row].Length) {
                    if (matrix[row][col] == '1') {
                        histogram[col] += 1;
                    } else {
                        histogram[col] = 0;
                    }
                }
 
                // Compute area
                while (stack.Count > 0 && histogram[stack.Peek()] >= histogram[col]) {
                    var area = histogram[stack.Pop()] * (stack.Count == 0 ? col : (col - stack.Peek() - 1));
                    result = Math.Max(result, area);
                }
                stack.Push(col);
            }
        }
        return result;
    }
}// http://programmingnotes.org/

QUICK NOTES:
The highlighted lines are sections of interest to look out for.

The code is heavily commented, so no further insight is necessary. If you have any questions, feel free to leave a comment below.

Once compiled, you should get this as your output for the example cases:

6 0 0 1 0

C# || How To Find The Largest Component Size By Common Factor Using C#

November 28, 2021 admin No comments

The following is a module with functions which demonstrates how to find the largest component size by common factor using C#.

1. Largest Component Size – Problem Statement

You are given an integer array of unique positive integers nums. Consider the following graph:

There are nums.length nodes, labeled nums[0] to nums[nums.length – 1],
There is an undirected edge between nums[i] and nums[j] if nums[i] and nums[j] share a common factor greater than 1.

Return the size of the largest connected component in the graph.

Example 1:

Input: nums = [4,6,15,35] Output: 4

Example 2:

Input: nums = [20,50,9,63] Output: 2

Example 3:

Input: nums = [2,3,6,7,4,12,21,39] Output: 8

2. Largest Component Size – Solution

The following is a solution which demonstrates how to find the largest component size by common factor.

The following solution uses a union find set to group connections together.





		
		
			2. Largest Component Size - Solution
			
C#
			
			// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Nov 28, 2021
//    Taken From: http://programmingnotes.org/
//    File:  Solution.cs
//    Description: Demonstrates how to find largest common factor
// ============================================================================
public class Solution {
    public int LargestComponentSize(int[] nums) {
        var set = new UnionFindSet(nums.Max() + 1);

        // Calculate primes set for all elements
        foreach (var num in nums) {
            for (var k = 2; k * k <= num; ++k) {
                if (num % k == 0) {
                    set.Union(num, k);
                    set.Union(num, num / k);
                }
            }
        }

        // Count the apperance of parents, return the maxium one.
        // All connected nodes will point to same parent
        var map = new Dictionary<int, int>();
        var result = 1;
        foreach (var num in nums) {
            var count = set.Find(num);
            map[count] = (map.ContainsKey(count) ? map[count] : 0) + 1;
            result = Math.Max(result, map[count]);
        }
        return result;
    }

    public class UnionFindSet {
        private int[] parent;

        public UnionFindSet(int size) {
            parent = new int[size];
            for (int i = 0; i < parent.Length; ++i) {
                parent[i] = i;
            }
        }
        public void Union(int x, int y) {
            parent[Find(x)] = parent[Find(y)];
        }
        public int Find(int x) {
            if (parent[x] != x) {
                parent[x] = Find(parent[x]);
            }
            return parent[x];
        }
    }
}// http://programmingnotes.org/
			
				
					
				
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						// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Nov 28, 2021
//    Taken From: http://programmingnotes.org/
//    File:  Solution.cs
//    Description: Demonstrates how to find largest common factor
// ============================================================================
public class Solution {
    public int LargestComponentSize(int[] nums) {
        var set = new UnionFindSet(nums.Max() + 1);
 
        // Calculate primes set for all elements
        foreach (var num in nums) {
            for (var k = 2; k * k <= num; ++k) {
                if (num % k == 0) {
                    set.Union(num, k);
                    set.Union(num, num / k);
                }
            }
        }
 
        // Count the apperance of parents, return the maxium one.
        // All connected nodes will point to same parent
        var map = new Dictionary<int, int>();
        var result = 1;
        foreach (var num in nums) {
            var count = set.Find(num);
            map[count] = (map.ContainsKey(count) ? map[count] : 0) + 1;
            result = Math.Max(result, map[count]);
        }
        return result;
    }
 
    public class UnionFindSet {
        private int[] parent;
 
        public UnionFindSet(int size) {
            parent = new int[size];
            for (int i = 0; i < parent.Length; ++i) {
                parent[i] = i;
            }
        }
        public void Union(int x, int y) {
            parent[Find(x)] = parent[Find(y)];
        }
        public int Find(int x) {
            if (parent[x] != x) {
                parent[x] = Find(parent[x]);
            }
            return parent[x];
        }
    }
}// http://programmingnotes.org/

QUICK NOTES:
The highlighted lines are sections of interest to look out for.

The code is heavily commented, so no further insight is necessary. If you have any questions, feel free to leave a comment below.

Once compiled, you should get this as your output for the example cases:

4 2 8

C# || Accounts Merge – How To Merge A List Of Emails Using C#

November 28, 2021 admin No comments

The following is a module with functions which demonstrates how to merge a list of emails using C#.

1. Accounts Merge – Problem Statement

Given a list of accounts where each element accounts[i] is a list of strings, where the first element accounts[i][0] is a name, and the rest of the elements are emails representing emails of the account.

Now, we would like to merge these accounts. Two accounts definitely belong to the same person if there is some common email to both accounts. Note that even if two accounts have the same name, they may belong to different people as people could have the same name. A person can have any number of accounts initially, but all of their accounts definitely have the same name.

After merging the accounts, return the accounts in the following format: the first element of each account is the name, and the rest of the elements are emails in sorted order. The accounts themselves can be returned in any order.

Example 1:

Input: accounts = [["John","johnsmith@mail.com","john_newyork@mail.com"],["John","johnsmith@mail.com","john00@mail.com"],["Mary","mary@mail.com"],["John","johnnybravo@mail.com"]] Output: [["John","john00@mail.com","john_newyork@mail.com","johnsmith@mail.com"],["Mary","mary@mail.com"],["John","johnnybravo@mail.com"]] Explanation: The first and second John's are the same person as they have the common email "johnsmith@mail.com". The third John and Mary are different people as none of their email addresses are used by other accounts. We could return these lists in any order, for example the answer [['Mary', 'mary@mail.com'], ['John', 'johnnybravo@mail.com'], ['John', 'john00@mail.com', 'john_newyork@mail.com', 'johnsmith@mail.com']] would still be accepted.

Example 2:

Input: accounts = [["Gabe","Gabe0@m.co","Gabe3@m.co","Gabe1@m.co"],["Kevin","Kevin3@m.co","Kevin5@m.co","Kevin0@m.co"],["Ethan","Ethan5@m.co","Ethan4@m.co","Ethan0@m.co"],["Hanzo","Hanzo3@m.co","Hanzo1@m.co","Hanzo0@m.co"],["Fern","Fern5@m.co","Fern1@m.co","Fern0@m.co"]] Output: [["Ethan","Ethan0@m.co","Ethan4@m.co","Ethan5@m.co"],["Gabe","Gabe0@m.co","Gabe1@m.co","Gabe3@m.co"],["Hanzo","Hanzo0@m.co","Hanzo1@m.co","Hanzo3@m.co"],["Kevin","Kevin0@m.co","Kevin3@m.co","Kevin5@m.co"],["Fern","Fern0@m.co","Fern1@m.co","Fern5@m.co"]]

2. Accounts Merge – Solution

The following is a solution which demonstrates how to merge a list of emails.

The following solution uses a union find set to group accounts with matching emails together.





		
		
			2. Accounts Merge - Solution
			
C#
			
			// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Nov 28, 2021
//    Taken From: http://programmingnotes.org/
//    File:  Solution.cs
//    Description: Demonstrates how to merge a list of emails
// ============================================================================
public class Solution {
    public IList<IList<string>> AccountsMerge(IList<IList<string>> accounts) {
        var set = new UnionFindSet(accounts.Count);

        // Map email to their component index
        var emailComponents = new Dictionary<string, int>();
        for (int i = 0; i < accounts.Count; ++i) {
            var account = accounts[i];

            for (int j = 1; j < account.Count; ++j) {
                var email = account[j];

                // Assign component group as the account index
                var group = i;
                if (!emailComponents.ContainsKey(email)) {
                    emailComponents[email] = group;
                } else {
                    // Union this group with the previous group of the email
                    set.Union(group, emailComponents[email]);
                }
            }
        }

        // Store emails corresponding to the components parent
        var emailGroups = new Dictionary<int, List<string>>();
        foreach (var email in emailComponents.Keys) {
            var group = emailComponents[email];
            var groupParent = set.Find(group);

            if (!emailGroups.ContainsKey(groupParent)) {
                emailGroups[groupParent] = new List<string>();
            }
            emailGroups[groupParent].Add(email);
        }

        // Sort the emails and add the account name
        var result = new List<IList<string>>();
        foreach (var group in emailGroups.Keys) {
            var emails = emailGroups[group];
            emails.Sort(StringComparer.Ordinal);
            emails.Insert(0, accounts[group][0]);
            result.Add(emails);
        }
        return result;
    }

    public class UnionFindSet {
        int[] parent;
        int[] size;

        public UnionFindSet(int count) {
            parent = new int[count];
            size = new int[count];
            for (int index = 0; index < count; ++index) {
                parent[index] = index;
                size[index] = 1;
            }
        }
        public int Find(int x) {
            if (parent[x] != x) {
                parent[x] = Find(parent[x]);
            }
            return parent[x];
        }
        public void Union(int x, int y) {
            var parentX = Find(x);
            var parentY = Find(y);
            if (parentX == parentY) {
                return;
            }
            if (size[parentX] >= size[parentY]) {
                size[parentX] += size[parentY];
                parent[parentY] = parentX;
            } else {
                size[parentY] += size[parentX];
                parent[parentX] = parentY;
            }
        }
    }
}// http://programmingnotes.org/
			
				
					
				
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						// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Nov 28, 2021
//    Taken From: http://programmingnotes.org/
//    File:  Solution.cs
//    Description: Demonstrates how to merge a list of emails
// ============================================================================
public class Solution {
    public IList<IList<string>> AccountsMerge(IList<IList<string>> accounts) {
        var set = new UnionFindSet(accounts.Count);
 
        // Map email to their component index
        var emailComponents = new Dictionary<string, int>();
        for (int i = 0; i < accounts.Count; ++i) {
            var account = accounts[i];
 
            for (int j = 1; j < account.Count; ++j) {
                var email = account[j];
 
                // Assign component group as the account index
                var group = i;
                if (!emailComponents.ContainsKey(email)) {
                    emailComponents[email] = group;
                } else {
                    // Union this group with the previous group of the email
                    set.Union(group, emailComponents[email]);
                }
            }
        }
 
        // Store emails corresponding to the components parent
        var emailGroups = new Dictionary<int, List<string>>();
        foreach (var email in emailComponents.Keys) {
            var group = emailComponents[email];
            var groupParent = set.Find(group);
 
            if (!emailGroups.ContainsKey(groupParent)) {
                emailGroups[groupParent] = new List<string>();
            }
            emailGroups[groupParent].Add(email);
        }
 
        // Sort the emails and add the account name
        var result = new List<IList<string>>();
        foreach (var group in emailGroups.Keys) {
            var emails = emailGroups[group];
            emails.Sort(StringComparer.Ordinal);
            emails.Insert(0, accounts[group][0]);
            result.Add(emails);
        }
        return result;
    }
 
    public class UnionFindSet {
        int[] parent;
        int[] size;
 
        public UnionFindSet(int count) {
            parent = new int[count];
            size = new int[count];
            for (int index = 0; index < count; ++index) {
                parent[index] = index;
                size[index] = 1;
            }
        }
        public int Find(int x) {
            if (parent[x] != x) {
                parent[x] = Find(parent[x]);
            }
            return parent[x];
        }
        public void Union(int x, int y) {
            var parentX = Find(x);
            var parentY = Find(y);
            if (parentX == parentY) {
                return;
            }
            if (size[parentX] >= size[parentY]) {
                size[parentX] += size[parentY];
                parent[parentY] = parentX;
            } else {
                size[parentY] += size[parentX];
                parent[parentX] = parentY;
            }
        }
    }
}// http://programmingnotes.org/

QUICK NOTES:
The highlighted lines are sections of interest to look out for.

The code is heavily commented, so no further insight is necessary. If you have any questions, feel free to leave a comment below.

Once compiled, you should get this as your output for the example cases:

[["John","john00@mail.com","john_newyork@mail.com","johnsmith@mail.com"],["Mary","mary@mail.com"],["John","johnnybravo@mail.com"]] [["Gabe","Gabe0@m.co","Gabe1@m.co","Gabe3@m.co"],["Kevin","Kevin0@m.co","Kevin3@m.co","Kevin5@m.co"],["Ethan","Ethan0@m.co","Ethan4@m.co","Ethan5@m.co"],["Hanzo","Hanzo0@m.co","Hanzo1@m.co","Hanzo3@m.co"],["Fern","Fern0@m.co","Fern1@m.co","Fern5@m.co"]]

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