luogu 2142 高精度减法

#include <iostream>
#include <string>
#include <cstring>
using namespace std;
int main()
{
    string a,b,tmp;
    int x[11000] = {},y[11000] = {},z[11000] = {};
    int ok = 0;
    cin >> a >> b;
    if ((a.length() < b.length()) || ((a.length() == b.length()) && a < b))
    {
        tmp = a;
        a = b;
        b = tmp;
        ok = 1;
    }
    for (int i = 0;i < a.length();i++)
        x[a.length() - i] = a[i] - '0';
    for (int i = 0;i < b.length();i++)
        y[b.length() - i] = b[i] - '0';
    int len = 1;
    while (len <= a.length() || len <= b.length())
    {
        if (x[len] < y[len])
        {
            x[len] = x[len] + 10;
            x[len + 1] = x[len + 1] - 1; 
        }
        z[len] = x[len] - y[len];
        len++;
    }
    while (z[len] == 0 && len >= 1)
        len--;
    if (len == 0)
        len = 1; 
    if (ok == 1)
        cout << "-";
    for (int i = len;i >= 1;i--)
        cout << z[i];
    return 0;
}