C++ || 8 Different Ways To Reverse A String/Character Array In C++
This page will consist of 8 different ways to reverse a character array, and a string literal (std::string).
REQUIRED KNOWLEDGE FOR THE PROGRAMS
Character Arrays
String Literals
Cin.getline - Use For Char Arrays
Getline - Use For std::string
Length
Strlen
Strcpy
While Loops
For Loops
Recursion - What is it?
#include < algorithm>
#include < stack>
The methods on this page will be broken up into sections. This page will list:
(3) methods which reverses string literals (std::string)
(4) methods which reverses character arrays
(1) method which utilizes the stack to "reverse" a character sequence
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 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 |
#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
Enter your name: My Programming NotesYour name reversed is: setoN gnimmargorP yM
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 |
#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
Enter your name: My Programming NotesYour name reversed is: setoN gnimmargorP yM
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 |
#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
Enter your name: My Programming NotesYour name reversed is: setoN gnimmargorP yM
======= REVERSE A CHARACTER ARRAY =======
The following will demonstrate (4) methods which reverses a character array.
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 |
#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
Enter your name: My Programming NotesYour name reversed is: setoN gnimmargorP yM
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 |
#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
Enter your name: My Programming NotesYour name reversed is: setoN gnimmargorP yM
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 |
#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
Enter your name: My Programming NotesYour name reversed is: setoN gnimmargorP yM
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 |
#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
Enter your name: My Programming NotesYour name reversed is: setoN gnimmargorP yM
======= REVERSE A CHARACTER SEQUENCE USING A STACK =======
The following will demonstrate (1) method which reverses a character sequence using the STL stack.
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 |
#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
Enter your name: My Programming NotesYour name reversed is: setoN gnimmargorP yM
Hi, I'm a software engineer. I write articles about programming and design in my spare time.
Thanks for all these methods!
I am slightly at a loss as to why 1 has been subtracted from strlen(name) in method 7.
int nameLength = strlen(name)-1;
I am a newbie on C++ so can you please enlighten me on this?
Hello, thanks for visiting!
To answer your question, its because arrays in C++ are zero based instead of one based. That means that the first element in an array/string starts at index 0 instead of index 1.
To illustrate, the string “My Programming Notes” for example, is 20 characters long. If you wanted to iterate through that string, index zero would contain the letter “M”, index 1 would contain the letter “y” and so forth.
Since the first letter in the string starts at index zero (instead of at index one), that means the last character in the string is located at the length of the string minus one.
So in the example above, the last character in the string “My Programming Notes” is located at index 19 (since 20 is the length of the string minus one)
That is why the statement “int nameLength = strlen(name)-1;” is present in the code.
Hope this helps