C PROGRAMMING PROGRAM • POINTERS & DYNAMIC MEMORY

Reverse a String Using Pointers

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

IntermediateCharacter pointersTwo-pointer methodstrlen()

PROBLEM UNDERSTANDING

Input and expected output

Sample input

CodeBhavya

Sample output

Reversed = ayvahBedoC

COMPLETE C PROGRAM

Complete C implementation

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

int main(void)
{
    char text[100];
    printf("Enter text: ");
    fgets(text, sizeof text, stdin);
    text[strcspn(text, "\n")] = '\0';
    char *left = text;
    char *right = text + strlen(text);
    if (right != left) right--;
    while (left < right) {
        char temporary = *left;
        *left++ = *right;
        *right-- = temporary;
    }
    printf("Reversed = %s\n", text);
    return 0;
}

CURRENT STEP

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SELECTED LINE

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EXPECTED OUTPUT FOR THE SAMPLE

Reversed = ayvahBedoC

0%Step 0 of 0

PROGRAM EXPLANATION

Algorithm and explanation

Read the required input values.
Point at both ends of the mutable string and exchange characters while the pointers move inward.
Display the computed result.

Point at both ends of the mutable string and exchange characters while the pointers move inward.

EFFICIENCY

Time and space complexity

Time complexity

O(n)

Auxiliary space

O(1)

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.