Checking if a given String is a Palindrome or not in C

Here’s a step-by-step guide and a simple C program to check if a given string is a palindrome:

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

// Function to check if the string is a palindrome
int isPalindrome(char str[]) {
    int start = 0;
    int end = strlen(str) - 1;

    while (start < end) {
        if (str[start] != str[end]) {
            return 0; // Not a palindrome
        }
        start++;
        end--;
    }
    return 1; // Is a palindrome
}

int main() {
    char str[100]; // Declare a string of size 100

    // Input the string
    printf("Enter a string: ");
    scanf("%s", str);

    // Check if the string is a palindrome
    if (isPalindrome(str)) {
        printf("The string '%s' is a palindrome.\n", str);
    } else {
        printf("The string '%s' is not a palindrome.\n", str);
    }

    return 0;
}

Detailed Explanation

• Include Headers: We include the necessary header files. stdio.h for standard input/output functions and string.h for string functions.

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

• Palindrome Check Function: We define a function isPalindrome that takes a string as input and checks if it is a palindrome.

int isPalindrome(char str[]) {
    int start = 0;
    int end = strlen(str) - 1;

    while (start < end) {
        if (str[start] != str[end]) {
            return 0; // Not a palindrome
        }
        start++;
        end--;
    }
    return 1; // Is a palindrome
}

• We initialize two indices, start and end, pointing to the beginning and end of the string.
• We use a loop to compare characters from the start and end of the string. If any characters don’t match, the function returns 0, indicating that the string is not a palindrome.
• If all characters match, the function returns 1, indicating that the string is a palindrome.

• Main Function: In the main function, we handle user input and call the isPalindrome function.

int main() {
    char str[100]; // Declare a string of size 100

    // Input the string
    printf("Enter a string: ");
    scanf("%s", str);

    // Check if the string is a palindrome
    if (isPalindrome(str)) {
        printf("The string '%s' is a palindrome.\n", str);
    } else {
        printf("The string '%s' is not a palindrome.\n", str);
    }

    return 0;
}

• We declare a character array str to store the input string.
• We use scanf to read the input string. Note that scanf will read a single word (i.e., it stops reading at a space).
• We call the isPalindrome function to check if the string is a palindrome.
• We print the result based on the return value of the isPalindrome function.

Testing the Program

When you run the program, it will prompt you to enter a string. For example:

Enter a string: radar
The string 'radar' is a palindrome.

Or:

Enter a string: hello
The string 'hello' is not a palindrome.

Conclusion

Checking if a string is a palindrome is a fundamental exercise for beginners to understand string manipulation and basic conditional statements in C programming. This program provides a simple and clear way to check if a string is a palindrome by comparing characters from the start and end of the string. Feel free to leave your questions or comments below if you need further assistance or clarification. Happy coding!