C语言：判断回文字符串

#include<stdio.h>
#include<string.h>
#define LEN 100

int huiwen(char *s){
    if((s == NULL) || (*s == NULL))
        return 0;
    char *a = s;
    int i = 0,j = 0;
    while(*a != '\0'){
        a++;
        i++;
    }
    a--;
    while(*s != '\0'){
        if(*s == *a)
            j++;
        else
            return 0;
        s++;
        a--;
    }
    
    if(j == i)
        return 1;    
}

int main(){
    char s[LEN];
    scanf("%s",&s);
    if(huiwen(s) == 1)
        printf("True");
    else
        printf("False");
    return 0;
}