高精度减法用string 和 stack

#include "bits/stdc++.h"
using namespace std;

int main()
{
    string a,b;
    while(cin >> a >> b)
    {
        if(a.size() < b.size() || (a.size() == b.size() && a < b))
        {
            cout << "-";
            swap(a,b);
        }

        int lena = a.size();
        int lenb = b.size();

        for(int i = ;i < lena - lenb;i++)
            b = '' + b;

        int jiewei = ;
        stack<int>s;
        for(int i = lena-; i >=;i--)
        {
            int v = a[i] - b[i] + jiewei;
            s.push(v >=  ? v:v+);
            jiewei = (v >=  ? :-);
        }
        while(s.top() == )
        {
            s.pop();
        }
        while(!s.empty())
        {
            cout << s.top();
            s.pop();
        }

    }
    return ;
}

我觉得多用用这些数据结构也是蛮好的；