不容易系列之(4)——考新郎

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 long long int c,m,n,cuopai[25];
 4 long long int C(int n,int m){
 5     if(m == n || m == 0)
 6         return 1;
 7     else if(m == 1)
 8         return n;
 9     else
10         return C(n - 1,m - 1) + C(n - 1,m);
11 }
12 void init(){
13     cuopai[1] = 0,cuopai[2] = 1;
14     for(int i = 3;i <= 20;i++)
15         cuopai[i] = (i - 1) * (cuopai[i - 2] + cuopai[i - 1]);
16     return;
17 }
18 int main(){
19     init();//错排打表
20     scanf("%lld",&c);
21     while(c--){
22         scanf("%lld%lld",&n,&m);
23         printf("%lld\n",C(n,m) * cuopai[m]);
24     }
25     return 0;
26 }