Palindrome.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#define MAX_SIZE 100
struct
{
    int top;
    char items[MAX_SIZE];
} typedef Stack;

char pop(Stack* s)
{
    if(s->top == -1)
        return 0;
    return s->items[s->top--] ;
}

void push(Stack* s, char item)
{
    s->items[++s->top] = item;
}
/**
 *  @function cmp_alphanum
 *  @returns (int) returns 1 if they are equal. 0 if they are not equal
 *  @argument a (char[]) first string
 *  @argument b (char[]) second string
 *  Compare two string ignoring spaces and special charectors
 */
int cmp_alphanum(char a[MAX_SIZE], char b[MAX_SIZE])
{
    int i=0, j=0, n = strlen(a);
    while(i<n &&j<n)
    {
        while(i<n && a[i]==' ')
            i++; //increment i until no spaces are encountered
        while(j<n && b[j]==' ')
            j++; //increment j until no spaces are encountered
        if(a[i]!=b[j])
            return 0;//they are not equal. return 0
        i++;//increment i
        j++;//increment j
    }
    return 1;//they are equal. return 1
}

int main()
{
    char orginal_string[MAX_SIZE] = {0}, final_string[MAX_SIZE] = {0};
    char *temp;
    Stack s;
    s.top = -1;
    puts("Enter a string");
    gets((char*)orginal_string);
    if(strlen(orginal_string) == 0){
        puts("Enter valid string");
        return 0;
    }
    temp = orginal_string;
    while(*temp != 0)
    {
        push(&s,*temp);
        temp++;
    }
    temp = final_string;
    while((*temp = pop(&s))){
        temp++;
    }
    *(++temp) = 0;
    
    printf("Reverse of given string is\n%s\n",(char*)final_string);
    
    if(cmp_alphanum(orginal_string, final_string))
        puts("String is a palindrome");
    else
        puts("String is not a palindrome");
        
    return 0;
}