Lähetit

#include <iostream>
using namespace std;
typedef long long ll;

const ll mod=1e9+7;

ll dp1[111][211];
ll dp2[111][211];

int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    int n,k;
    cin>>n>>k;
    if (k>2*n){
        cout<<0<<endl;
        return 0;
    }
    int o=n;
    int e=n*2-1-o;
    dp1[0][0]=1;
    for (int i=0;i<o;i++){
        for (int j=0;j<=k;j++){
            int s=i+1;
            if (s%2==0) s--;
            dp1[i+1][j]+=dp1[i][j];
            dp1[i+1][j]%=mod;

            if (s>j){
                dp1[i+1][j+1]+=(ll)dp1[i][j]*(s-j);
                dp1[i+1][j+1]%=mod;
            }
        }
    }

    dp2[0][0]=1;
    for (int i=0;i<e;i++){
        for (int j=0;j<=k;j++){
            int s=i+2;
            if (s%2==1) s--;
            dp2[i+1][j]+=dp2[i][j];
            dp2[i+1][j]%=mod;

            if (s>j){
                dp2[i+1][j+1]+=(ll)dp2[i][j]*(s-j);
                dp2[i+1][j+1]%=mod;
            }
        }
    }
    ll v=0;
    for (int j=0;j<=k;j++){
        v+=dp1[o][j]*dp2[e][k-j];
        v%=mod;
    }
    cout<<v<<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