Thread: What's problem of adding two binary number?

The problem appears in [url]http://acm.hnu.cn:8080/online/?action=problem&type=show&id=10475[\url]
Just very simple method, first I reverse the binary number. Then I fill the zero in the remaining space. For example, a = 1001011111, b = 11110001.

Code:

1) reverse
1001011111 ---> 1111101001
11110001 ---> 10001111
2) fill zero
10001111 ---> 1000111100
3) adding two binary number
1111101001
1000111100
--------------
1101010000

Here is my code

Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAXDIGIT 100 

char a[MAXDIGIT], b[MAXDIGIT];
int n;

void reverse(char *x)
{
	char tmp;
	int i, len = strlen(x);
	for (i = 0; i < len/2; i++) {
		tmp = x[i];
		x[i] = x[len-i-1];
		x[len-i-1] = tmp;
	}
}

void fillZero(char *a, char *b)
{
	int i;
	if (strlen(a) > strlen(b)) {
		for (i = strlen(b); i < strlen(a); i++)
			b[i] = '0';
		i++;
		b[i] = '\0';
	} else if (strlen(a) < strlen(b)) {
		for (i = strlen(a); i < strlen(b); i++)
			a[i] = '0';
		i++;
		a[i] = '\0';
	}
}

int chr2int(char x)
{ return (int)x-'0'; }

void base2Plus()
{
	int i, tmp, len;
	int result[MAXDIGIT];
	reverse(a);
	reverse(b);
	fillZero(a, b);
	tmp = 0;
	for (i = 0, len = 0; i < strlen(a); i++, len++) {
		tmp += chr2int(a[i])+chr2int(b[i]);
		result[len] = tmp%2;
		tmp = (tmp <= 1) ? 0 : 1;
	}
	if (tmp == 1) {
		result[len] = tmp%2;
		len++;
	}
	for (i = len-1; i >= 0; i--)
		printf("%d", result[i]);
	printf("\n");
}

int main()
{
	int i;
	scanf("%d", &n);
	for (i = 1; i <= n; i++) {
		scanf("%s %s", a, b);
		printf("%d ", i);
		base2Plus();
	}
	return 0;
}

But I cannot pass the task of the mentioned problem. What are the bugs here?