Submission #1148755

#	Time	Username	Problem	Language	Result	Execution time	Memory
1148755		sonamoo	악수 (kriii4_D)	C++20	100 / 100	145 ms	5760 KiB

D

#include <bits/stdc++.h>
#define FastIO ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
#define pii pair<int,int>
#define ll long long int
#define SIZE 500005
#define all(v) v.begin(), v.end()
#define pb push_back
#define MOD 1000000007
#define INF 1000000007
using namespace std;

ll C[888][888] , D[888][888] , comb[888][888] , inv[888];

int main() {
    FastIO;

    int N , M;
    cin >> N;
    comb[0][0] = inv[1] = comb[1][0] = comb[1][1] = 1;
    for (int i = 2; i < 800; i++) {
        comb[i][0] = 1;
        for (int j = 1; j <= i; j++) comb[i][j] = (comb[i-1][j-1]+comb[i-1][j])%MOD;
        inv[i] = (inv[MOD%i]*(MOD-MOD/i))%MOD;
    }

    C[1][0] = 1LL; D[1][0] = 1LL;
    for (int n = 2; n <= N; n++) {
        M = n*(n-1)/2;
        for (int k = n-1; k <= M; k++) {
            for (int i = 1; i <= n-1; i++) {
                for (int j = 0; j <= k-1; j++) {
                    ll ret = (comb[n-1][i-1]*comb[k-1][j])%MOD;
                    ret *= D[i][j]; ret %= MOD;
                    ret *= D[n-i][k-j-1]; ret %= MOD;
                    ret *= i; ret %= MOD;
                    ret *= (n-i); ret %= MOD;
                    C[n][k] += ret; C[n][k] %= MOD;
                }
            }
            D[n][k] = C[n][k];
            D[n][k] += ((M-(k-1))*D[n][k-1])%MOD; D[n][k] %= MOD;
        }
    }

    ll ans=0 , tmp = 1LL;
    for (int k = 1; k <= M; k++) {
        tmp *= inv[M-k+1]; tmp %= MOD;
        ll ret = C[N][k]; ret *= tmp; ret %= MOD;
        ret *= k; ret %= MOD;
        ans += ret; ans %= MOD;
    }

    cout << ans;

    return 0;
}

• Subtask 1: 5 / 5
• Subtask 2: 95 / 95