USACO3.2.1 Factorials (fact4)

一边乘一边模，末尾有0就去掉。

也有更好的做法就是遇到2和5continue。

/*ID:shijiey1PROG:fact4LANG:C++*/#include <cstdio>#include <cstring>#include <algorithm>#include <iostream>using namespace std;int n;int s = 1;int main() {freopen("fact4.in", "r", stdin);freopen("fact4.out", "w", stdout);scanf("%d", &n);for (int i = 2; i <= n; i++) {s *= i;while (!(s % 10)) {s/= 10;}s %= 10000;// cout << i << ' ' << s << endl;}printf("%d\n", s % 10);return 0;}