[HAOI2009]逆序對數列

腦殘題，過

#include<bits/stdc++.h>
#define MAXN 2005
typedef long long ll;
using namespace std;

int n,k,f[MAXN][MAXN],g[MAXN];

int main(){
	memset(f , 0 , sizeof(f));
	cin>>n>>k;
	f[0][0] = 1;
	g[0] = 1;
	for(int i = 1 ; i <= n ; i++){
		for(int j = 0 ; j <= min(((i - 1) * i) >> 1 , k) ; j++){
			/*for(int p = 0 ; p < i ; p++){
				f[i][j] = (f[i][j] + f[i - 1][j - p]) % 10000;
			}*/
			f[i][j] = (g[j] - g[j - i] + 10000) % 10000;
			//cout<<i<<"  "<<j<<"  "<<f[i][j]<<endl;
		}
		for(int j = 1 ; j <= min(((i + 1) * i) >> 1 , k) ; j++){
			g[j] = (g[j - 1] + f[i][j] + 10000) % 10000;
		}
	}
	cout<<f[n][k]<<endl;
}