求逆序对

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<algorithm>
 4 #include<cstring>
 5 #include<cmath>
 6 using namespace std;
 7 const int maxn=107;
 8 const int mod=10000; 
 9 int n,K;
10 int f[maxn][maxn*maxn];
11 int main(){
12   cin>>n>>K;
13   f[0][0]=1;
14   for(int i=1;i<=n;i++){
15     for(int j=0;j<=K;j++){
16       for(int k=0;k<=i-1&&j-k>=0;k++){
17         f[i][j]+=f[i-1][j-k];f[i][j]%=mod;
18       }
19     }
20   }
21   cout<<f[n][K]%mod<<endl;
22 }