C Program to Check for Palindrome String

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

char *strrev(char *str) {
    int len = strlen(str);
  
  	// Temporary char array to store the
    // reversed string
    char *rev = (char *)malloc
      (sizeof(char) * (len + 1));
  
    // Reversing the string
    for (int i = 0; i < len; i++) {
        rev[i] = str[len - i - 1];
    }
    rev[len] = '\0';
    return rev;
}

void isPalindrome(char *str) {

    // Reversing the string
    char *rev = strrev(str);

    // Check if the original and reversed
  	// strings are equal
    if (strcmp(str, rev) == 0)
        printf("\"%s\" is palindrome.\n",
               str);
    else
        printf("\"%s\" is not palindrome.\n",
               str);
}

int main() {
    
  	// Cheking for palindrome strings
	isPalindrome("madam");
  	isPalindrome("hello");

    return 0;
}

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

void isPalindrome(char *str) {
 	
  	// Index pointer to the start
    int left = 0;
  
    // Index pointer to the end
    int right = strlen(str) - 1;

    // Run the loop till both pointer
    // meet
    while (left < right) {
      
        // If characters don't match,
        // string is not palindrome
        if (str[left] != str[right]) {
            printf("\"%s\" is not palindrome.\n",
               str);
            return;
        }

        // Move both pointers towards
        // each other
        left++;
        right--;
    }

    // If all characters match,
    // string is palindrome
    printf("\"%s\" is palindrome.\n",
               str);
}

int main() {
	
  	// Checking if given strings are palindrome
  	isPalindrome("madam");
  	isPalindrome("hello");
  	return 0;
}

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

bool palinHelper(char *s, int left, int right) {

    // If the start and end pointers cross
    // each other, it means all characters
    // have matched
    if (left >= right)
        return true;

    // If characters don't match,
    // string is not palindrome
    if (s[left] != s[right])
        return false;

    // Recursively check for the rest of
    // the string
    return palinHelper(s, left + 1, right - 1);
}

void isPalindrome(char* s) {
  
  	// Calling the recursive function to check
    // palindrome string
    if (palinHelper(s, 0, strlen(s) - 1))
        printf("\"%s\" is palindrome.\n", s);
    else
        printf("\"%s\" is not palindrome.\n", s);
}

int main() {
  
    // Checking if the given strings are palindrome
    isPalindrome("madam");
    isPalindrome("hello");
    return 0;
}