UVa 1638 Pole Arrangement【递推】

 1 #include<iostream>  
 2 #include<cstdio>  
 3 #include<cstring> 
 4 #include <cmath> 
 5 #include<stack>
 6 #include<vector>
 7 #include<map> 
 8 #include<set>
 9 #include<queue> 
10 #include<algorithm>  
11 using namespace std;
12 
13 #define foreach(i,c) for (__typeof(c.begin()) i = c.begin(); i != c.end(); ++i)
14 
15 typedef long long LL;
16 const int INF = (1<<30)-1;
17 const int mod=1000000007;
18 const int maxn=1000005;
19 
20 unsigned long long d[25][25][25];
21 
22 int main(){
23     int T;
24     scanf("%d",&T);
25     while(T--){
26         int n,l,r;
27         cin>>n>>l>>r;
28         
29         memset(d,0,sizeof(d));
30         d[1][1][1]=1;
31         
32         for(int i=2;i<=n;i++){
33             for(int j=1;j<=i;j++){
34                 for(int k=1;k<=i;k++){
35                     d[i][j][k]=d[i-1][j-1][k]+d[i-1][j][k-1]+d[i-1][j][k]*(i-2);
36                 }            
37             }
38         }
39         
40         printf("%llu\n",d[n][l][r]);        
41     }
42     return 0;
43 }