Submission #529021

#	Time	Username	Problem	Language	Result	Execution time	Memory
529021		wiwiho	Tents (JOI18_tents)	C++14	100 / 100	212 ms	70840 KiB

tents

#include<bits/stdc++.h>

#define printv(a, b) { \
    for(auto pv : a) b << pv << " "; \
    b << "\n"; \
}

using namespace std;

typedef long long ll;

const ll MOD = 1000000007;

ll C2(ll n){
    if(n < 2) return 0;
    return n * (n - 1) / 2;
}

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(0);

    int n, m;
    cin >> n >> m;

    vector<vector<ll>> dp(n + 1, vector<ll>(m + 1));
    for(int i = 0; i <= n; i++) dp[i][0] = 1;
    for(int i = 0; i <= m; i++) dp[0][i] = 1;
    for(int sz = 2; sz <= n + m; sz++){
        for(int i = 1; i < sz; i++){
            int j = sz - i;
            if(i > n || j > m) continue;

            if(j >= 2) dp[i][j] += dp[i - 1][j - 2] * i % MOD * (j - 1) % MOD;
            if(i >= 2) dp[i][j] += dp[i - 2][j - 1] * C2(i) % MOD;
            dp[i][j] += 4LL * i * dp[i - 1][j - 1] % MOD;
            dp[i][j] += dp[i][j - 1];
            dp[i][j] %= MOD;
        }
    }

    //for(int i = 0; i <= n; i++) printv(dp[i], cerr);

    ll ans = dp[n][m];
    ans--;
    ans = (ans % MOD + MOD) % MOD;

    cout << ans << "\n";

    return 0;
}

• Subtask 1: 48 / 48
• Subtask 2: 52 / 52