Lähetit

#include <iostream>
using namespace std;
typedef long long ll;
ll dp[256][256];
const int Z = 1e9+7;
int main() {
	int n,k;
	cin>>n>>k;
	if (k>2*n) {
		cout<<0<<'\n';
		return 0;
	}
	if (n==1||k==0) {
		cout<<1<<'\n';
		return 0;
	}
	dp[0][0]=1;
	dp[1][0]=1;
	dp[1][1]=2;
	for(int i=2; i<n; ++i) {
		dp[i][0]=dp[i+2][0];
		for(int j=0; j<=i; ++j) {
			dp[i][j] += dp[i-2][j];
			if (j>0) dp[i][j] += 2*(i-j+1)*dp[i-2][j-1];
			if (j>1) dp[i][j] += (i-j+2)*(i-j+1)*dp[i-2][j-2];
			dp[i][j]%=Z;
		}
	}
	for(int i=0; i<=n; ++i) dp[n][i]=(dp[n-2][i]+(i>0 ? (n-i+1)*dp[n-2][i-1] : 0))%Z;
	ll res=0;
	for(int i=0; i<=k; ++i) res+=dp[n-1][i]*dp[n][k-i],res%=Z;
	cout<<res<<'\n';
}

Test 1

Group: 1

Verdict: ACCEPTED

Test 2

Group: 1

Verdict: ACCEPTED

Test 3

Group: 1

Verdict: ACCEPTED

Test 4

Group: 1

Verdict: ACCEPTED

Test 5

Group: 1

Verdict: ACCEPTED

Test 6

Group: 2

Verdict: ACCEPTED

Test 7

Group: 2

Verdict: ACCEPTED

Test 8

Group: 2

Verdict: ACCEPTED

Test 9

Group: 2

Verdict: ACCEPTED

Test 10

Group: 2

Verdict: ACCEPTED

Test 11

Group: 3

Verdict: ACCEPTED

Test 12

Group: 3

Verdict: ACCEPTED

Test 13

Group: 3

Verdict: ACCEPTED

Test 14

Group: 3

Verdict: ACCEPTED

Test 15

Group: 3

Verdict: ACCEPTED