Lähetit

#include <iostream>
using namespace std;
long long M=1000000007;
int n, k;

long long b[201][55];
long long w[201][55];


int main(){
  cin >> n >> k;
  if (k>2*n-1) cout << 0 << endl;
  else{
    for (int i=0; i<=n/2+1; ++i){b[0][i]=1; w[0][i]=1;}
    
    for (int a=1; a<=n; ++a){
      //black
      for (int d=1; d<=(n+1)/2; ++d){
        int c=d*2-1;
        if (2*d!=n+1){
          b[a][d]=b[a][d-1]+b[a-1][d-1]*2*(c-a+1);
          if (a>1) b[a][d]+=b[a-2][d-1]*(c-a+2)*(c-a+1);
        }else{
          b[a][d]=b[a][d-1]+b[a-1][d-1]*(c-a+1);
        }
        b[a][d]%=M;
      }
      //white
      for (int d=1; d<=n/2; ++d){
        int c=d*2;
        if (2*d!=n){
          w[a][d]=w[a][d-1]+w[a-1][d-1]*2*(c-a+1);
          if (a>1) w[a][d]+=w[a-2][d-1]*(c-a+2)*(c-a+1);
        }else{
          w[a][d]=w[a][d-1]+w[a-1][d-1]*(c-a+1);
        }
        w[a][d]%=M;
      }
    }
    long long a=0;
    for (int i=0; i<=k; ++i){
      a+=w[i][n/2]*b[k-i][(n+1)/2];
      a%=M;
    }
    cout << a << endl;
  }
}

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