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C++ || Char Array – Palindrome Number Checker Using A Character Array, Strlen, Strcpy, & Strcmp

July 10, 2012 admin No comments

The following is a palindromic number checking program, which demonstrates more use of character array’s, Strlen, & Strcmp.

Want sample code for a palindrome checker which works for numbers and words? Click here.

REQUIRED KNOWLEDGE FOR THIS PROGRAM

This program first asks the user to enter a number that they wish to compare for similarity. If the number which was entered into the system is a palindrome, the program will prompt a message to the user via cout. This program determines similarity by using the strcmp function to compare two arrays together. Using a for loop, this program also demonstrates how to reverse a character array, aswell as demonstrates how to determine if the text contained in a character array is a number or not.

This program will repeatedly prompt the user for input until an “exit code” is obtained. The designated exit code in this program is the number 0 (zero). So the program will not stop asking for user input until the number 0 is entered into the program.





		
		
			Palindrome Number Checker Using A Char Array
			
C++
			
			// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Jul 10, 2012
//    Taken From: http://programmingnotes.org/
//    File:  palindrome.cpp
//    Description: Palindrome number checker
// ============================================================================
#include <iostream>
#include <cctype>
#include <cstring>
#include <cstdlib>
using namespace std;

// function prototypes
void Reverse(char arry[]);
bool IsArryANum(char arry[]);

// constant, which is the exit value 
const char* EXIT_VALUE = "0";

int main()
{
    // declare variables
    char arry[80];
    char arryReversed[80];
    
    do{// get data from user using do/while loop
        cout<<"\nEnter a positive integer, or ("<<EXIT_VALUE<<") to exit: ";
        
        cin >> arry;
        
        if(atoi(arry) < 0) // check for negative numbers
        {
            cout <<"\n*** Error: "<<arry<<" must be greater than zero\n";
        }
        else if(!IsArryANum(arry)) // check for any letters 
        {
            cout <<"\n*** Error: "<<arry<<" is not an integer\n";
        }
        else if(strcmp(EXIT_VALUE, arry) == 0) // check for "exit code"
        {
            cout <<"\nExiting program...\n";
        }
        else // if all else is good, determine if number is a palindrome 
        {
            // copy the user input from the first array (arry)
            // into the second array (arryReversed)
            strcpy(arryReversed, arry);

            // function call to reverse the contents inside the
            // "arryReversed" array to check for similarity
            Reverse(arryReversed);
            
            cout <<endl<<arry;

            // use strcmp to determine if the two arrays are the same
            if(strcmp(arryReversed, arry) == 0)
            {
                cout <<" is a Palindrome..\n";
            }
            else
            {
                cout <<" is NOT a Palindrome!\n";
            }
        }
    }while(strcmp(EXIT_VALUE, arry) != 0); // keep going until user enters the exit value

    cout <<"\nBYE!\n";
    
    return 0;
}// end of main

void Reverse(char arry[])
{
    // get the length of the current word in the array index
    int length = strlen(arry)-1;
    
    // increment thru each letter within the current char array index
    // reversing the order of the array
    for (int currentChar=0; currentChar < length; --length, ++currentChar)
    {
        // copy 1st letter in the array index into temp
        char temp = arry[currentChar];
        // copy last letter in the array index into the 1st array index
        arry[currentChar] = arry[length];
        // copy temp into last array index
        arry[length] = temp;
    }
}// end of Reverse

bool IsArryANum(char arry[])
{
    // LOOP UNTIL U REACH THE NULL CHARACTER,
    // AKA THE END OF THE CHAR ARRAY
    for(int x=0; arry[x]!='\0'; ++x)
    {               
        // if the current char isnt a number,
        // exit the loop & return false
        if(!isdigit(arry[x])) 
        {
            return false;
        }
    }
    return true;
}// http://programmingnotes.org/
			
				
					
				
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						// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Jul 10, 2012
//    Taken From: http://programmingnotes.org/
//    File:  palindrome.cpp
//    Description: Palindrome number checker
// ============================================================================
#include <iostream>
#include <cctype>
#include <cstring>
#include <cstdlib>
using namespace std;
 
// function prototypes
void Reverse(char arry[]);
bool IsArryANum(char arry[]);
 
// constant, which is the exit value 
const char* EXIT_VALUE = "0";
 
int main()
{
    // declare variables
    char arry[80];
    char arryReversed[80];
    
    do{// get data from user using do/while loop
        cout<<"\nEnter a positive integer, or ("<<EXIT_VALUE<<") to exit: ";
        
        cin >> arry;
        
        if(atoi(arry) < 0) // check for negative numbers
        {
            cout <<"\n*** Error: "<<arry<<" must be greater than zero\n";
        }
        else if(!IsArryANum(arry)) // check for any letters 
        {
            cout <<"\n*** Error: "<<arry<<" is not an integer\n";
        }
        else if(strcmp(EXIT_VALUE, arry) == 0) // check for "exit code"
        {
            cout <<"\nExiting program...\n";
        }
        else // if all else is good, determine if number is a palindrome 
        {
            // copy the user input from the first array (arry)
            // into the second array (arryReversed)
            strcpy(arryReversed, arry);
 
            // function call to reverse the contents inside the
            // "arryReversed" array to check for similarity
            Reverse(arryReversed);
            
            cout <<endl<<arry;
 
            // use strcmp to determine if the two arrays are the same
            if(strcmp(arryReversed, arry) == 0)
            {
                cout <<" is a Palindrome..\n";
            }
            else
            {
                cout <<" is NOT a Palindrome!\n";
            }
        }
    }while(strcmp(EXIT_VALUE, arry) != 0); // keep going until user enters the exit value
 
    cout <<"\nBYE!\n";
    
    return 0;
}// end of main
 
void Reverse(char arry[])
{
    // get the length of the current word in the array index
    int length = strlen(arry)-1;
    
    // increment thru each letter within the current char array index
    // reversing the order of the array
    for (int currentChar=0; currentChar < length; --length, ++currentChar)
    {
        // copy 1st letter in the array index into temp
        char temp = arry[currentChar];
        // copy last letter in the array index into the 1st array index
        arry[currentChar] = arry[length];
        // copy temp into last array index
        arry[length] = temp;
    }
}// end of Reverse
 
bool IsArryANum(char arry[])
{
    // LOOP UNTIL U REACH THE NULL CHARACTER,
    // AKA THE END OF THE CHAR ARRAY
    for(int x=0; arry[x]!='\0'; ++x)
    {               
        // if the current char isnt a number,
        // exit the loop & return false
        if(!isdigit(arry[x])) 
        {
            return false;
        }
    }
    return true;
}// 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

C++ || 8 Different Ways To Reverse A String/Character Array In C++

March 01, 2012 admin 2 Comments

This page will consist of 8 different ways to reverse a character array, and a string literal (std::string).

REQUIRED KNOWLEDGE FOR THE PROGRAMS

The methods on this page will be broken up into sections. This page will list:

Some methods listed on this page demonstrates the use of reversing a character sequence without the use of strlen/length.

======= REVERSE AN STD::STRING =======





		
		
			#1 - Reverse String Using STL Function
			
C++
			
			#include <iostream>
#include <algorithm>
#include <string>
using namespace std;

int main()
{
	// declare variable
	string name="";

	cout << "Enter your name: ";
	getline(cin,name);

	// built in C++ function to reverse an std::string
	reverse(name.begin(), name.end());
	
	cout <<"\nYour name reversed is: " <<name << endl;

	return 0;
}// http://programmingnotes.org/
			
				
					
				
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						#include <iostream>
#include <algorithm>
#include <string>
using namespace std;
 
int main()
{
	// declare variable
	string name="";
 
	cout << "Enter your name: ";
	getline(cin,name);
 
	// built in C++ function to reverse an std::string
	reverse(name.begin(), name.end());
	
	cout <<"\nYour name reversed is: " <<name << endl;
 
	return 0;
}// http://programmingnotes.org/

SAMPLE OUTPUT





		
		
			#2 - Reverse String Recursive Method, No Length()
			
C++
			
			#include <iostream>
#include <string>
using namespace std;

// function prototypes
void Reverse(string name);

int main()
{
	// declare variable
	string name="";

	// get user data
	cout<<"Enter your name: ";
	getline(cin,name);

	cout<<"\nYour name reversed is: ";

	// function declaration
	Reverse(name);
	cout<<endl;

	return 0;
}// end of main

void Reverse(string name)
{
	if(name == "") // the base case
	{
		return;
	}
	else // the recursive step
	{
		Reverse(name.substr(1));			
		cout<<name.at(0);
	}
}// http://programmingnotes.org/
			
				
					
				
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						#include <iostream>
#include <string>
using namespace std;
 
// function prototypes
void Reverse(string name);
 
int main()
{
	// declare variable
	string name="";
 
	// get user data
	cout<<"Enter your name: ";
	getline(cin,name);
 
	cout<<"\nYour name reversed is: ";
 
	// function declaration
	Reverse(name);
	cout<<endl;
 
	return 0;
}// end of main
 
void Reverse(string name)
{
	if(name == "") // the base case
	{
		return;
	}
	else // the recursive step
	{
		Reverse(name.substr(1));			
		cout<<name.at(0);
	}
}// http://programmingnotes.org/

SAMPLE OUTPUT





		
		
			#3 - Reverse String Iterative Method, Using Length()
			
C++
			
			#include <iostream>
#include <string>
using namespace std;

// function prototypes
void Reverse(string name);

int main()
{
	// declare variable
	string name="";

	// get user data
	cout<<"Enter your name: ";
	getline(cin,name);

	cout<<"\nYour name reversed is: ";

	// function declaration
	Reverse(name);
	cout<<endl;

	return 0;
}// end of main

void Reverse(string name)
{
	// get the length of the string
	int nameLength = name.length()-1;

	while(nameLength >= 0)
	{
		cout<<name[nameLength];
		--nameLength;
	}
}// http://programmingnotes.org/
			
				
					
				
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						#include <iostream>
#include <string>
using namespace std;
 
// function prototypes
void Reverse(string name);
 
int main()
{
	// declare variable
	string name="";
 
	// get user data
	cout<<"Enter your name: ";
	getline(cin,name);
 
	cout<<"\nYour name reversed is: ";
 
	// function declaration
	Reverse(name);
	cout<<endl;
 
	return 0;
}// end of main
 
void Reverse(string name)
{
	// get the length of the string
	int nameLength = name.length()-1;
 
	while(nameLength >= 0)
	{
		cout<<name[nameLength];
		--nameLength;
	}
}// http://programmingnotes.org/

SAMPLE OUTPUT

======= REVERSE A CHARACTER ARRAY =======

The following will demonstrate (4) methods which reverses a character array.





		
		
			#4 - Reverse Char Array Recursive Method, No Strlen
			
C++
			
			#include <iostream>
using namespace std;

// function prototype
void Reverse(char name[]);

int main()
{
	// declare variable
	char name[30];

	// get user data
	cout<<"Enter your name: ";
	cin.getline(name, sizeof(name));

	cout<<"\nYour name reversed is: ";

	// function declaration
	Reverse(name);
	cout<<endl;

	return 0;
}// end of main

void Reverse(char name[])
{
	if(*name=='\0') // the base case
	{
		return;
	}
	else // the recursive step
	{
		Reverse(name+1);
		cout<<*(name);
	}
}// http://programmingnotes.org/
			
				
					
				
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						#include <iostream>
using namespace std;
 
// function prototype
void Reverse(char name[]);
 
int main()
{
	// declare variable
	char name[30];
 
	// get user data
	cout<<"Enter your name: ";
	cin.getline(name, sizeof(name));
 
	cout<<"\nYour name reversed is: ";
 
	// function declaration
	Reverse(name);
	cout<<endl;
 
	return 0;
}// end of main
 
void Reverse(char name[])
{
	if(*name=='\0') // the base case
	{
		return;
	}
	else // the recursive step
	{
		Reverse(name+1);
		cout<<*(name);
	}
}// http://programmingnotes.org/

SAMPLE OUTPUT





		
		
			#5 - Reverse Char Array Iterative Method, No Strlen
			
C++
			
			#include <iostream>
using namespace std;

// function prototypes
void Reverse(char name[]);

int main()
{
	// declare variable
	char name[30];

	// get user data
	cout<<"Enter your name: ";
	cin.getline(name, sizeof(name));

	cout<<"\nYour name reversed is: ";

	// function declaration
	Reverse(name);
	cout<<endl;

	return 0;
}// end of main

void Reverse(char name[])
{
	int nameLength = 0;

	//get the length of array
	while(name[nameLength] != '\0')
	{
		++nameLength;
	}

	//decrease the length of by 1
	--nameLength;

	// display reversed string
	while(nameLength >= 0)
	{
		cout<<name[nameLength];
		--nameLength;
	}
}// http://programmingnotes.org/
			
				
					
				
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						#include <iostream>
using namespace std;
 
// function prototypes
void Reverse(char name[]);
 
int main()
{
	// declare variable
	char name[30];
 
	// get user data
	cout<<"Enter your name: ";
	cin.getline(name, sizeof(name));
 
	cout<<"\nYour name reversed is: ";
 
	// function declaration
	Reverse(name);
	cout<<endl;
 
	return 0;
}// end of main
 
void Reverse(char name[])
{
	int nameLength = 0;
 
	//get the length of array
	while(name[nameLength] != '\0')
	{
		++nameLength;
	}
 
	//decrease the length of by 1
	--nameLength;
 
	// display reversed string
	while(nameLength >= 0)
	{
		cout<<name[nameLength];
		--nameLength;
	}
}// http://programmingnotes.org/

SAMPLE OUTPUT





		
		
			#6 - Reverse Char Array Iterative Method, No Strlen
			
C++
			
			#include <iostream>
#include <cstring>
using namespace std;

// function prototypes
void Reverse(char name[]);

int main()
{
	// declare variable
	char name[30];

	// get user data
	cout<<"Enter your name: ";
	cin.getline(name, sizeof(name));

	// function declaration
	Reverse(name);

	cout<<"\nYour name reversed is: "<< name<<endl;

	return 0;
}// end of main

void Reverse(char name[])
{
	// private variables
	int nameLength = 0;
	char copy[30];

	strcpy(copy,name);

	//get lenght of array
	while(name[nameLength] != '\0')
	{
		++nameLength;
	}

	//decrease the length of by 1
	--nameLength;

	// reverse the array
	for(int x = 0; x <= nameLength; ++x)
	{
		// rearange the order of the two arrays
		name[nameLength - x] = copy[x];
	}	
}// http://programmingnotes.org/
			
				
					
				
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						#include <iostream>
#include <cstring>
using namespace std;
 
// function prototypes
void Reverse(char name[]);
 
int main()
{
	// declare variable
	char name[30];
 
	// get user data
	cout<<"Enter your name: ";
	cin.getline(name, sizeof(name));
 
	// function declaration
	Reverse(name);
 
	cout<<"\nYour name reversed is: "<< name<<endl;
 
	return 0;
}// end of main
 
void Reverse(char name[])
{
	// private variables
	int nameLength = 0;
	char copy[30];
 
	strcpy(copy,name);
 
	//get lenght of array
	while(name[nameLength] != '\0')
	{
		++nameLength;
	}
 
	//decrease the length of by 1
	--nameLength;
 
	// reverse the array
	for(int x = 0; x <= nameLength; ++x)
	{
		// rearange the order of the two arrays
		name[nameLength - x] = copy[x];
	}	
}// http://programmingnotes.org/

SAMPLE OUTPUT





		
		
			#7 - Reverse Char Array Iterative Method, Using Strlen
			
C++
			
			#include <iostream>
#include <cstring>
using namespace std;

// function prototypes
void Reverse(char name[]);

int main()
{
	// declare variable
	char name[30];

	// get user data
	cout<<"Enter your name: ";
	cin.getline(name, sizeof(name));

	// function declaration
	Reverse(name);

	cout<<"\nYour name reversed is: "<< name<<endl;

	return 0;
}// end of main

void Reverse(char name[])
{
	// get the length of the current word in the array index
	int nameLength = strlen(name)-1;
	
	// increment thru each letter within the current char array index
	// reversing the order of the array
	for(int currentChar=0; currentChar < nameLength; --nameLength, ++currentChar)
	{
		// copy 1st letter in the array index into temp
		char temp = name[currentChar]; 
		// copy last letter in the array index into the 1st array index
		name[currentChar] = name[nameLength];
		// copy temp into last array index
		name[nameLength] = temp;
	}
}// http://programmingnotes.org/
			
				
					
				
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						#include <iostream>
#include <cstring>
using namespace std;
 
// function prototypes
void Reverse(char name[]);
 
int main()
{
	// declare variable
	char name[30];
 
	// get user data
	cout<<"Enter your name: ";
	cin.getline(name, sizeof(name));
 
	// function declaration
	Reverse(name);
 
	cout<<"\nYour name reversed is: "<< name<<endl;
 
	return 0;
}// end of main
 
void Reverse(char name[])
{
	// get the length of the current word in the array index
	int nameLength = strlen(name)-1;
	
	// increment thru each letter within the current char array index
	// reversing the order of the array
	for(int currentChar=0; currentChar < nameLength; --nameLength, ++currentChar)
	{
		// copy 1st letter in the array index into temp
		char temp = name[currentChar]; 
		// copy last letter in the array index into the 1st array index
		name[currentChar] = name[nameLength];
		// copy temp into last array index
		name[nameLength] = temp;
	}
}// http://programmingnotes.org/

SAMPLE OUTPUT

======= REVERSE A CHARACTER SEQUENCE USING A STACK =======

The following will demonstrate (1) method which reverses a character sequence using the STL stack.





		
		
			#8 - Reverse Char Sequence Using Stack
			
C++
			
			#include <iostream>
#include <stack>
using namespace std;

// function prototypes
void Reverse(stack<char> &name);

int main()
{ 
	// using the internal system stack
	stack<char> name;
	char singleChar;
	
	cout<<"Enter your name: ";
	
	while(cin.get(singleChar) && singleChar != '\n')
	{
		name.push(singleChar);
	}
	
	cout<<"\nYour name reversed is: ";

	// function declaration
	Reverse(name);
	cout<<endl;

	return 0;
}// end of main

void Reverse(stack<char> &name)
{
	while(!name.empty())
	{
		cout << name.top();
		name.pop();
	}
}// http://programmingnotes.org/
			
				
					
				
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						#include <iostream>
#include <stack>
using namespace std;
 
// function prototypes
void Reverse(stack<char> &name);
 
int main()
{ 
	// using the internal system stack
	stack<char> name;
	char singleChar;
	
	cout<<"Enter your name: ";
	
	while(cin.get(singleChar) && singleChar != '\n')
	{
		name.push(singleChar);
	}
	
	cout<<"\nYour name reversed is: ";
 
	// function declaration
	Reverse(name);
	cout<<endl;
 
	return 0;
}// end of main
 
void Reverse(stack<char> &name)
{
	while(!name.empty())
	{
		cout << name.top();
		name.pop();
	}
}// http://programmingnotes.org/

SAMPLE OUTPUT

Tag Archives: reverse

C++ || Char Array – Palindrome Number Checker Using A Character Array, Strlen, Strcpy, & Strcmp

C++ || 8 Different Ways To Reverse A String/Character Array In C++

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