Program To Reverse a String in C using Pointer

Introduction

In this article, we will explore how to write a program to reverse a string in the C programming language using pointer.

In the world of programming, it’s often necessary to manipulate strings and perform various operations on them.

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One common task is to reverse a string, which means to rearrange the characters in the string in reverse order.

Understanding Pointers in C

Before we dive into reversing a string, let’s briefly discuss pointers in the C programming language.

Pointers are variables that store memory addresses. They allow us to directly manipulate memory locations and access the data stored in those locations.

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Pointers are particularly useful when dealing with strings and arrays.

Program To Reverse a String in C Using Pointer

To reverse a string in C using pointers, we need to understand how strings are represented in memory.

In C, a string is an array of characters terminated by a null character (‘\0’). We can use a pointer to iterate over the characters in the string and reverse their order.

Here’s an example program that demonstrates the process:

#include <stdio.h>

void reverseString(char *str) {
    // Initialize two pointers, one pointing to the start of the string and the other to the end
    char *start = str;
    char *end = str;
    
    // Move the end pointer to the last character of the string
    while (*end != '\0') {
        end++;
    }
    end--; // Move back one position to exclude the null character
    
    // Reverse the string by swapping characters
    while (start < end) {
        char temp = *start;
        *start = *end;
        *end = temp;
        
        start++;
        end--;
    }
}

int main() {
    char str[] = "Hello, World!";
    
    printf("Original string: %s\n", str);
    
    // Reverse the string
    reverseString(str);
    
    printf("Reversed string: %s\n", str);
    
    return 0;
}

In this program, we define a function reverseString that takes a pointer to a string as an argument.

We initialize two pointers, start and end, which initially point to the first character of the string.

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The while loop is used to move the end pointer to the last character of the string by iterating until we reach the null character (‘\0’).

We then move the end pointer back one position to exclude the null character.

Next, we use another while loop to reverse the string.

Inside the loop, we swap the characters pointed to by the start and end pointers and move them towards each other until they meet in the middle.

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Finally, we can test our program by calling the reverseString function on a sample string and printing the reversed string.

FAQs (Program To Reverse a String in C Using Pointer)

Conclusion

Reversing a string in C using pointers is a fundamental programming task.

By understanding the concept of pointers and the memory layout of strings, we can efficiently reverse a string in-place.

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The example program provided demonstrates the technique and can be used as a starting point for your own projects.

Remember to exercise caution when working with pointers to ensure proper memory management and avoid undefined behavior.

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With practice and a solid understanding of pointers, you can confidently reverse strings and perform various string manipulation tasks in the C programming language.