Palindrome checking without using string.h

One of my friends, who is learning to program in C, asked me about how to write a program which checks an inputed string is a palindrome or not, without using the header file string.h

So here's the solution.

Code:

#include <stdio.h>

void main(void)
{
    char str[50];
    int len=0,i=0,j,flag=1;
    
    printf("Enter a string: ");
    gets(str);
    
    while(str[i++]!='\0')
        len++;

    for(i=0,j=(len-1);i<len/2;i++,j--)
    {
        if(str[j]!=str[i])
        {
            flag=0;
            break;
        }
    }
        
    if(flag==1)
        printf("String is a palindrome");
    else
        printf("String is not a palindrome");

}

 

good in logical thiking

 

Superb Sir