C PROGRAMMING PROGRAM • FUNCTIONS & RECURSION

Reverse a String Using Recursion

Learn how to reverse a string using recursion using a clear C program.

IntermediateRecursionStringsTwo pointers

PROBLEM UNDERSTANDING

Input and expected output

Sample input

recursion

Sample output

Reversed: noisrucer

COMPLETE C PROGRAM

Complete C implementation

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

void reverse(char text[], int left, int right)
{
    if (left >= right) return;
    char temporary = text[left]; text[left] = text[right]; text[right] = temporary;
    reverse(text, left + 1, right - 1);
}

int main(void)
{
    char text[200];

    fgets(text, sizeof text, stdin);
    text[strcspn(text, "\n")] = '\0';
    reverse(text, 0, (int) strlen(text) - 1);
    printf("Reversed: %s\n", text);
    return 0;
}

CURRENT STEP

Select Start to walk through the important lines.

SELECTED LINE

No line selected

EXPECTED OUTPUT FOR THE SAMPLE

Reversed: noisrucer

0%Step 0 of 0

PROGRAM EXPLANATION

Algorithm and explanation

Read the required input values.
Swap the outer characters and recursively process the smaller inner substring.
Display the computed result.

Swap the outer characters and recursively process the smaller inner substring.

EFFICIENCY

Time and space complexity

Time complexity

O(n)

Auxiliary space

O(n)

DEBUGGING CHECKLIST

Common mistakes

Check this

Use the correct format specifier for every variable.

Check this

Initialize variables before using their values.

Check this

Check braces, semicolons and input order carefully.

Try it yourself

Practice: Run the program with the sample input, predict its output, and then test one boundary case of your own.