C program to reverse a string using pointers

Reversing a string is a common task in programming that can be approached in various ways. In C, pointers provide a powerful tool to manipulate strings efficiently. This article will guide you through writing a C program to reverse a string using pointers.

Understanding Pointers and Strings in C

In C, a string is an array of characters ending with a null character (\0). Pointers, which store memory addresses, allow direct manipulation of array elements, making operations like reversing a string straightforward and efficient.

Steps to Reverse a String

1. Initialize pointers: Use pointers to point to the start and end of the string.
2. Swap characters: Swap characters from the start and end, moving towards the center.
3. Continue until pointers meet: Ensure all characters are swapped by the time the pointers meet in the middle.

Write a C program to find reverse of a string using pointers

Here is a simple C program to reverse a string using pointers:

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

// Function to reverse a string using pointers
void reverseString(char *str) {
    // Pointers pointing to the start and end of the string
    char *start = str;
    char *end = str + strlen(str) - 1;
    char temp;

    // Swap characters from start and end moving towards the center
    while (start < end) {
        // Swap the characters
        temp = *start;
        *start = *end;
        *end = temp;

        // Move the pointers towards the center
        start++;
        end--;
    }
}

int main() {
    char str[100];

    // Input a string from the user
    printf("Enter a string: ");
    gets(str);

    // Reverse the string
    reverseString(str);

    // Output the reversed string
    printf("Reversed string: %s", str);

    return 0;
}

Output

Enter a string: ProCoding
Reversed string: gnidoCorP

Explanation

1. Input Handling:
   • The program reads a string from the user using gets.
2. String Reversal Function:
   • The reverseString function takes a char * pointer (the string) as an argument.
   • Two pointers, start and end, are initialized to point to the beginning and the end of the string, respectively.
   • A while loop swaps the characters at the start and end pointers, then moves the pointers towards the center until they meet.
3. Swapping Logic:
   • A temporary variable temp is used to facilitate the swap of characters.
   • The start pointer is incremented, and the end pointer is decremented after each swap.
4. Output:
   • The main function calls reverseString and then prints the reversed string.

Benefits of Using Pointers

• Efficiency: Direct manipulation of memory addresses can be faster than using array indices.
• Flexibility: Pointers can be easily manipulated to point to different parts of the array, providing more control.