hdu 2048 神、上帝以及老天爷 错排应用

#include <stdio.h>#include <string.h>#include <iostream>#include <algorithm>#include <vector>#include <queue>#include <stack>#include <set>#include <map>#include <string>#include <math.h>#include <stdlib.h>#include <time.h>using namespace std;typedef long long ll;int main(){    int _,n,i;    ll f[25],c[25];    double a[25];    f[1]=0;f[2]=1;    for(i=3;i<=20;i++)        f[i]=(i-1)*(f[i-2]+f[i-1]);    for(i=2,c[1]=1;i<=20;i++)        c[i]=i*c[i-1];    for(i=1;i<=20;i++)        a[i]=1.0*f[i]/c[i]*100;    scanf("%d",&_);    while(_--)    {        scanf("%d",&n);        printf("%.2f%%\n",a[n]);    }    return 0;}