In this tutorial, we will write a C++ Program to Reverse a String. There are three different ways to reverse a string.
- Using library function, reverse()
- Using loops instead of reverse()
- Using recursion
However, using recursion is discussed in the next tutorial, you will get the link down below. Before beginning, you must be familiar with the following topics in C++.
Reverse a String in C++
The program takes user input for the string and then reverses it using various ways.
1. C++ Program to Reverse a String using reverse() function
Question: reverse a string in c++ using library function.
The reverse() is a built-in function provided in C++ to reverse a string. This function is defined in an algorithm header file which needs to be included at the beginning of the program.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 | #include <iostream> #include <algorithm> using namespace std; int main() { string str; cout << "Enter the string: "; cin >> str; reverse(str.begin(), str.end()); cout << "Reversed String: " << str; return 0; } |
Output:
Enter the string: simple2code
Reversed String: edocp2elmis
2. How to Reverse a String in C++ using while loop
Here the program uses a while loop to iterate and reverse the string.
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 | #include <iostream> using namespace std; int main() { char str[50], temp; int length, i = 0, j; cout << "Enter the String: "; cin >> str; //getting the length of a string while (str[i] != '\0') i++; length = i; i = 0; j = length - 1; //swapping to reverse the string while (i < j) { temp = str[i]; str[i] = str[j]; str[j] = temp; i++; j--; } cout << "Reversed string " << str; return 0; } |
Output:
Enter the String: programs
Reversed string smargorp
You can use strlen() function to calculate the length of a string and use that to iterate using a while loop.
3. Reverse a String in C++ using for loops
Here the program uses a for loop. The program uses strlen() function to calculate the length of a string then uses that value to iterate through the string.
Since you are using one of the string built-in functions, make sure to include string.h header file in a program.
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 | #include <iostream> #include <string.h> using namespace std; int main() { char str[50], temp; int length, i = 0, j; cout << "Enter the String: "; cin >> str; //getting the length of a string length = strlen(str); j = length - 1; //swapping to reverse the string for (i = 0; i < j; i++, j--) { temp = str[i]; str[i] = str[j]; str[j] = temp; } cout << "Reversed string " << str; return 0; } |
Output:
Enter the String: programs
Reversed string smargorp
You may go through the following program on a string.