神、上帝以及老天爷 HDU

神、上帝以及老天爷

 HDU - 2048

错排~

c[n] = (n-1) * (c[n-1] + c[n-2]);

c[1] = 0; c[2] = 1;

#include <bits/stdc++.h>
using namespace std;
#define ll long long
const int mod = 20090126;
const int maxn = 21;
ll c[maxn], f[maxn];
void init(){
    c[1] = 0;
    c[2] = 1;
    for(int i = 3; i < maxn; i++) {
        c[i] = (i-1) * (c[i-1] + c[i-2]);
    }
    f[1] = 1;
    for(int i = 2; i < maxn; i++) f[i] = f[i-1] * i;
}
int main(){
    int n;
    int t;
    scanf("%d", &t);
    init();
    while(t--) {
        scanf("%d", &n);
        printf("%.2lf",c[n]*100.0/f[n]);
        puts("%");
    }
}