C Program to find the reverse of a String using recursion

In this C Programming example, we will implement the program to find the reverse of a String using recursion and print the output on the console.

1. Reverse of a String using recursion

To reverse a string using recursion, we swap the characters from the beginning of the string with the last character, the second character with the second last, and so on until all the values are swapped once i.e. till we reach the middle of the string.

Example: 
Input: hello world
Output: dlrow olleh

Helpful topics to understand this program better are-

• Data Types in C
• Console Input / Output in C
• Functions in C
• Recursive functions in C

2. C Program to reverse a string using recursion

Let’s discuss the execution(kind of pseudocode) for the program to find the reverse of a string using recursion in C.

1. Initially, the program will prompt the user to enter a string.
2. Here, gets(input) will hold the string entered by the user and passes the string in the reverse(char *input, int begin, int end) function and then a recursive call reverse is made.
3. Here, in the reverse(char *input, int begin, int end) function, the n^th value from the beginning is swapped with the nth value from the end till we reach the middle of the string.
4. Now, all the characters are reversed and then printed on the console.

Let us now implement the above execution of the program to find the reverse of a string using recursion in C.

#include <stdio.h>
#include <string.h>

void reverse(char *input, int begin, int end) {
  char temp;

  if (begin >= end)
    return;

  temp = *(input + begin);
  *(input + begin) = *(input + end);
  *(input + end) = temp;

  reverse(input, ++begin, --end);
}

int main() {
  char input[100];
  printf("Enter the string or characters -> ");
  gets(input);
  reverse(input, 0, strlen(input) - 1);
  printf("Reversed string -> %s", input);
  return 0;
}

Note: In the above program the characters must be entered under the declared range char[100].

Output
Enter the string or characters -> Codingeek
Reversed string -> keegnidoC

3. Conclusion

In this C Programming example, we have discussed how to find the reverse of a string using recursion in C.

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