Submission #1276243

#	Time	Username	Problem	Language	Result	Execution time	Memory
1276243		hoa208	Tents (JOI18_tents)	C++20	100 / 100	237 ms	71248 KiB

tents

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define FOR(i, a, b) for (int i = (a), _b = (b); i <= _b; i++)
#define FORD(i, b, a) for (int i = (b), _a = (a); i >= _a; i--)
#define pa pair<ll, ll>
#define fi first
#define se second
#define bit(mask, j) ((mask >> j) & 1)
const   ll mod = 1e9 + 7;
const   ll INF = 1e18;
//--------------------------------------------------------------------
ll n, m;
const ll N = 3003;
ll f[N][N];
ll dp(ll i, ll j) { // 
    if(i > n + 1) return 0;
    if(j < 0) return 0;
    if(i == n + 1) {
        return 1;
    }
    if(f[i][j] != -1) return f[i][j];
    ll res = 0;
    res += dp(i + 1, j);
    res %= mod;
    res += dp(i + 1, j - 1) * j * 4 % mod;
    res %= mod;
    res += dp(i + 2, j - 1) * j * i % mod; 
    res %= mod;
    res += dp(i + 1, j - 2) * (j * (j - 1) / 2) % mod;
    res %= mod;
    return f[i][j] = res;
}
void hbmt() {
    memset(f, -1, sizeof f);
    cin >> n >> m;
    cout << (dp(1, m) - 1 + mod) % mod;
}

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

    #define NAME "hbmt"
    if(fopen(NAME".inp", "r")) {
        freopen(NAME".inp", "r", stdin);
        freopen(NAME".out", "w", stdout);
    }
    
    //int t;cin>>t;while(t--)
    hbmt();
    return 0;
}

Compilation message (stderr)

tents.cpp: In function 'int main()':
tents.cpp:47:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   47 |         freopen(NAME".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
tents.cpp:48:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   48 |         freopen(NAME".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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