Question

C Program

A palindrome consists of a word or deblanked, unpunctuated phrase that is spelled exactly the same when the letters are reversed. Write a recursive function that returns a value of 1 if its string argument is a palindrome. Notice that in palindromes such as level, deed, sees, and Madam I'm Adam (madamimadam), the first letter matches the last, the second matches the next-to-last, and so on.

Answer 1

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

int is_palindrome(char str[], int start, int end) {
    if(start < end) {
        return str[start] == str[end] && is_palindrome(str, start + 1, end - 1);
    } else {
        return 1;
    }
}

int main() {
    char str[100];
    while(1) {
        printf("Enter a string: ");
        scanf("%s", str);
        if(strcmp(str, "STOP") == 0 || strcmp(str, "stop") == 0 || strcmp(str, "Stop") == 0) {
            break;
        }
        if(is_palindrome(str, 0, strlen(str)-1)) {
            printf("%s is a palindrome\n", str);
        } else {
            printf("%s is not a palindrome\n", str);
        }
    }
    return 0;
}