最后一个样例错了，求9000000000 /1000000000，我的结果是0，答案应该是9.

#include <bits/stdc++.h>

using namespace std;

vector <int> div(vector <int> &A, int b, int &r)
{
    vector <int> c;
    r = 0;
    for(int i = A.size() - 1; i >= 0 ; --i)
    {
        r = r*10 + A[i];
        c.push_back(r/b);
        r = r%b;
    }

    reverse(c.begin(), c.end());
    while(c.size() > 1 && c.back() == 0) c.pop_back();
    return c;
}

int main()
{
    string a;
    int b;
    int r;
    cin>>a>>b;
    vector <int> A;
    A.clear();
    for(int i = a.size()-1; i >= 0; --i) A.push_back(a[i] - '0');
    auto c = div(A, b, r);
    for(int i = c.size()-1; i >= 0; --i) printf("%d", c[i]);
    return 0;
}