https://www.lanqiao.cn/problems/2167/learning/?subject_code=2&group_code=5&match_num=13&match_flow=2&origin=cup
1 import java.util.Scanner;
2 // 1:无需package
3 // 2: 类名必须Main, 不可修改
4
5 public class 小蓝选钥匙 {
6 public static void main(String[] args) {
7 Scanner sc = new Scanner(System.in);
8 long a =14;
9 long n1 = 28;
10 long m = 14;
11 System.out.println(C(n1,m)*D(a));
12
13 }//全错排列 错位的14把
14 static long D(long a){
15 if(a==0||a==1){
16 return 0;
17 }
18 else if(a==2){
19 return 1;
20 }
21 else{
22 return (a-1)*(D(a-2)+D(a-1));
23 }
24 }
25 //组合C 14 28
26 static long C(long n,long m){
27 long res = 1L;
28 for(int i = 0;i<m;i++){
29 res = res*(n-i)/(i+1);
30 }
31 return res;
32 }
33 }
