Check if the given string is Palindrome or not in C

Understanding Palindrome

A palindrome is a string that reads the same forward and backward.

We will explore three different methods to check if a string is a palindrome using C.

Method 1: Using a Loop

This method iterates through the string and checks if it is a palindrome.

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

int isPalindrome(char str[]) {
    int l = 0, r = strlen(str) - 1;
    while (l < r) {
        if (str[l] != str[r])
            return 0;
        l++, r--;
    }
    return 1;
}

int main() {
    char str[] = "madam";
    if (isPalindrome(str))
        printf("Palindrome\n");
    else
        printf("Not a Palindrome\n");
    return 0;
}
            

Method 2: Using Recursion

This method checks palindrome property recursively.

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

int isPalindromeRecursive(char str[], int l, int r) {
    if (l >= r) return 1;
    if (str[l] != str[r]) return 0;
    return isPalindromeRecursive(str, l + 1, r - 1);
}

int main() {
    char str[] = "racecar";
    if (isPalindromeRecursive(str, 0, strlen(str) - 1))
        printf("Palindrome\n");
    else
        printf("Not a Palindrome\n");
    return 0;
}
            

Method 3: Using String Reverse

This method reverses the string and compares it with the original.

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

int main() {
    char str[] = "hello", rev[100];
    strcpy(rev, str);
    strrev(rev);
    if (strcmp(str, rev) == 0)
        printf("Palindrome\n");
    else
        printf("Not a Palindrome\n");
    return 0;
}