P1591 阶乘数码

// Problem: P1591 阶乘数码
// Contest: Luogu
// URL: https://www.luogu.com.cn/problem/P1591
// Memory Limit: 125 MB
// Time Limit: 1000 ms
// User: Pannnn

#include 

using namespace std;

vector mulByI(vector a, int b) {
    vector res;
    int pre = 0;
    for (int i = 0; i < a.size(); ++i) {
        pre += a[i] * b;
        res.push_back(pre % 10);
        pre /= 10;
    }
    while (pre) {
        res.push_back(pre % 10);
        pre /= 10;
    }
    return res;
}

vector getRes(int n) {
    vector res(1, 1);
    for (int i = 1; i <= n; ++i) {
        res = mulByI(res, i);
    }
    return res;
}

int main() {
    int t;
    cin >> t;
    while (t--) {
        int n, a;
        cin >> n >> a;
        vector res = getRes(n);
        long long cnt = 0;
        for (auto i : res) {
            if (i == a) {
                ++cnt;
            }
        }
        cout << cnt << endl;
    }
    return 0;
}