Light OJ 1005 - Rooks（DP）

#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<cmath>
#include<queue>
#include<vector>
#include<map>
using namespace std;
typedef unsigned long long LL;
const int INF = 1e9+7;
const int maxn = 105;
const int MOD = 9973;
LL dp[maxn][905];
void solve()
{
    for(int i=0; i<=30; i++)
        dp[i][0] = 1;

    for(int i=1; i<=30; i++)
    for(int j=1; j<=i; j++)
    {
        dp[i][j] = dp[i-1][j] + (2*(i-j)+1) * dp[i-1][j-1];
        if(j-2 >= 0)
            dp[i][j] += (i-j+1)*(i-j+1) * dp[i-1][j-2];
    }
}

int main()
{
    int T, n, k, cas = 1;
    solve();
    scanf("%d", &T);

    while(T--)
    {
        scanf("%d %d", &n, &k);
        printf("Case %d: %llu\n",cas++, dp[n][k]);
    }
    return 0;
}