请大家帮忙看一看我的代码哪里错了。 code:

#include <bits/stdc++.h>
using namespace std;
const int N = 10100;
string s1, s2;
int a[N], b[N], c[N], alen, blen, len;
char f = '+';
int main()
{
	ios::sync_with_stdio(false);
	std::cin.tie(nullptr);
	std::cout.tie(nullptr);
	memset(a, 0, sizeof(a));
	memset(b, 0, sizeof(b));
	memset(c, 0, sizeof(c));
	cin >> s1 >> s2;
	alen = s1.size(), blen = s2.size();
	if (alen < blen || (alen == blen && s1 < s2))
	{
		f = '-';
		swap(s1, s2);
	}
	for (int i = 0; i < alen; i++)
		a[alen - i - 1] = s1[i] - '0';
	for (int i = 0; i < blen; i++)
		b[blen - i - 1] = s2[i] - '0';
	len = max(alen, blen);
	for (int i = 0; i < len; i++)
	{
		if (a[i] < b[i])
		{
			a[i + 1] -= 1;
			a[i] += 10;
		}
		c[i] = a[i] - b[i];
	}
	for (int i = len - 1; i >= 0; i--)
		if (c[i] != 0)
		{
			len = i;
			break;
		}
	if (f == '-')
		cout << f;
	for (int i = len; i >= 0; i--)
		cout << c[i];
	return 0;
}