Submission #1065477

#	Time	Username	Problem	Language	Result	Execution time	Memory
1065477		phong	Tents (JOI18_tents)	C++17	100 / 100	195 ms	71300 KiB

tents

#include<bits/stdc++.h>

#define ll long long
#define int long long
const int nmax = 3e3 + 5, N = 1e6;
const ll oo = 1e9 + 1, base = 311;
const int lg = 19, M = 10;
const ll mod = 1e9 + 7, mod2 = 1e9 + 5277;
#define pii pair<int, int>
#define fi first
#define se second
#define endl "\n"
#define debug(a, n) for(int i = 1; i <= n; ++i) cout << a[i] << ' '; cout << "\n";
using namespace std;

int n, m, dp[nmax][nmax];
ll mul(ll a, ll b){
    return a * b % mod;
}
ll calc(int n, int m){
    if(n == 0 || m == 0) return 1;
    if(n < 0 || m < 0) return 0;
    if(dp[n][m] != -1) return dp[n][m];
    ll &res = dp[n][m];
    res = calc(n - 1, m);
    if(m >= 2){
        res += mul(calc(n - 1, m - 2), 1ll * m * (m - 1) / 2);
        res %= mod;
    }
    if(n >= 2){
       res += mul(calc(n - 2, m - 1), 1ll * (n - 1) * m);
       res %= mod;
    }
    res += mul(calc(n - 1, m - 1) * 4, m);
    res %= mod;
    return res;
}
main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);cout.tie(0);
//    freopen("code.inp", "r", stdin);
//    freopen("code.out", "w", stdout);
    cin >> n >> m;
    memset(dp, -1, sizeof dp);
    cout << calc(n, m) - 1;
}
/*
3 1
*/

Compilation message (stderr)

tents.cpp:38:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   38 | main(){
      | ^~~~

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