bzoj2431：[HAOI2009]逆序对数列

#include<cstdio>
#define maxn 1005
#define p 10000

int n,k,sum;
int f[maxn][maxn];

int main(){
scanf("%d%d",&n,&k);
f[0][0]=1;
for (int i=1;i<=n;i++){
sum=0;
for (int j=0;j<=k;j++){
if (j-i>=0) sum=(sum-f[i-1][j-i]+p)%p;
sum=(sum+f[i-1][j])%p;
f[i][j]=sum;
}
}
printf("%d\n",f
[k]);
return 0;
}