Submission #1284008

#	Time	Username	Problem	Language	Result	Execution time	Memory
1284008		nqc	Tents (JOI18_tents)	C++20	100 / 100	94 ms	70804 KiB

tents

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

#define fi first
#define se second
#define ll long long
#define ull unsigned long long
#define pii pair<int, int>
#define pll pair<ll, ll>
#define pli pair<ll, int>
#define debug(x) cout << #x << " = " << x << '\n'
#define all(a) a.begin(), a.end()
#define SZ(a) (int)(a).size()

const int N = 3e3 + 5;
const int mod = 1e9 + 7;
const ll inf64 = 3e18;
const int inf32 = 2e9 + 5;

ll add(ll a, ll b) {
    a += b;
    if(a < 0) a += mod;
    if(a >= mod) a -= mod;
    return a;
}
ll mul(ll a, ll b) { return a * b % mod; }

int n, m;
ll dp[N][N];

void solve() {
    cin >> n >> m;

    // dp[i][j] = so cach xep thoa man doi voi bang i*j
    dp[0][0] = 1;
    for(int i = 1; i <= n; i++) 
        dp[i][0] = 1;
    for(int i = 1; i <= m; i++) 
        dp[0][i] = 1;
    for(int i = 1; i <= n; i++) for(int j = 1; j <= m; j++) {
        dp[i][j] = add(dp[i][j], dp[i - 1][j]);

        // dat vao 1 cot trong
        // -> bang con lai la (i-1)*(j-1)
        if(i - 1 >= 0 && j - 1 >= 0) 
            dp[i][j] = add(dp[i][j], mul(dp[i - 1][j - 1], j * 4));

        // dat vao 1 cot da open -> mat 1 cot, 2 dong
        // -> bang con lai la (i-2)*(j-1)
        if(i - 2 >= 0 && j - 1 >= 0) 
            dp[i][j] = add(dp[i][j], mul(dp[i - 2][j - 1],(i - 1) * j));

        // dat vao 2 cot trong
        // -> bang con lai la (i-1)*(j-2)
        if(i - 1 >= 0 && j - 2 >= 0) 
            dp[i][j] = add(dp[i][j], mul(dp[i - 1][j - 2], j * (j - 1) / 2));


        // cout << i << ' ' << j << ' ' << dp[i][j] << '\n';
    }
    cout << add(dp[n][m], -1) << '\n';
}

int main() {
    auto start = chrono::steady_clock::now();

    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    if(fopen("input.txt", "r")) {
        freopen("input.txt", "r", stdin);
        freopen("output.txt", "w", stdout);
    }
    int test = 1; 
    // cin >> test;
    while(test--) solve();
    
    chrono::duration<double> elapsed {chrono::steady_clock::now() - start};
    cerr << "\n>> Runtime: " << elapsed.count() << "s\n";
}

Compilation message (stderr)

tents.cpp: In function 'int main()':
tents.cpp:69:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   69 |         freopen("input.txt", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
tents.cpp:70:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   70 |         freopen("output.txt", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~

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