Practice Sessions

#include <bits/stdc++.h>
using namespace std;
#define rep(i, a, b) for(int i=a;i<(b);++i)
#define all(x) begin(x),end(x)
#define sz(x) int((x).size())
using ll = long long;
using pii = pair<int,int>;
using vi = vector<int>;

const int M = 1e9+7;

int R[5001][5001][2];

int main() {
  int n, k;
  cin >> n >> k;
  if (n == k) {
    cout << "1\n";
    return 0;
  }
  rep(n0,1,n+1) {
    rep(k0,1,n0) {
      const int n1 = n0 - k0;
      R[n0][k0][0] = (R[n0][k0-1][0] + R[n1][min(n1,k0-1)][1]) % M;
      R[n0][k0][1] = (R[n0][k0-1][1] + R[n1][n1][0] - R[n1][k0][0] + M) % M;
    }
    R[n0][n0][0] = (R[n0][n0-1][0]+1) % M;
    R[n0][n0][1] = (R[n0][n0-1][1]+1) % M;
  }
  cout << (ll(R[n][k][0]) - R[n][k-1][0] + R[n][k][1] - R[n][k-1][1] + M*2) % M << '\n';
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: WRONG ANSWER

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: WRONG ANSWER

Test 8

Verdict: WRONG ANSWER

Test 9

Verdict: WRONG ANSWER

Test 10

Verdict: WRONG ANSWER

Test 11

Verdict: WRONG ANSWER

Test 12

Verdict: WRONG ANSWER

Test 13

Verdict: WRONG ANSWER

Test 14

Verdict: WRONG ANSWER

Test 15

Verdict: WRONG ANSWER

Test 16

Verdict: WRONG ANSWER

Test 17

Verdict: WRONG ANSWER

Test 18

Verdict: WRONG ANSWER

Test 19

Verdict: WRONG ANSWER

Test 20

Verdict: WRONG ANSWER