Submission #687625

#	Time	Username	Problem	Language	Result	Execution time	Memory
687625		QwertyPi	NoM (RMI21_nom)	C++14	100 / 100	167 ms	54264 KiB

Main

#include <bits/stdc++.h>
#define int long long
using namespace std;

int dp[2001][2001];
int a[2001], s[2001];
int c[2001][2001];
const int MOD = 1e9 + 7;

void chadd(int& x, int y) { x += y; x %= MOD; }

int C(int n, int r){
    if(r < 0 || r > n) return 0;
    return c[n][r];
}

int32_t main(){
    int N, M; cin >> N >> M;
    for(int i = 0; i < M; i++) a[i] = (N * 2 + i) / M;
    for(int i = 0; i < M; i++) s[i + 1] = s[i] + a[i];
    dp[0][0] = 1;
    for(int i = 0; i <= 2000; i++){
        c[i][0] = c[i][i] = 1;
        for(int j = 1; j < i; j++){
            c[i][j] = (c[i - 1][j - 1] + c[i - 1][j]) % MOD;
        }
    }
    for(int i = 0; i < M; i++){
        for(int j = 0; j <= N; j++){
            for(int k = 0; k <= a[i]; k++){
                int j2 = j + (a[i] - k) - k; if(j2 < 0 || j2 > N) continue;
                chadd(dp[i + 1][j2], dp[i][j] * C(j, k) % MOD * C(N - (s[i] + j) / 2, a[i] - k) % MOD);
            }
        }
    }

    int ans = dp[M][0];
    for(int i = 0; i < N; i++){
        ans = ans * 2 % MOD;   
    }
    for(int i = 0; i < M; i++){
        for(int j = 1; j <= a[i]; j++){
            ans = ans * j % MOD;
        }
    }
    cout << ans << endl;
}

• Subtask 1: 9 / 9
• Subtask 2: 12 / 12
• Subtask 3: 13 / 13
• Subtask 4: 18 / 18
• Subtask 5: 48 / 48