Submission #47518

#	Time	Username	Problem	Language	Result	Execution time	Memory
47518		qoo2p5	Tents (JOI18_tents)	C++17	0 / 100	3 ms	376 KiB

tents

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

const int INF = (int) 1e9 + 1e6 + 123;
const ll LINF = (ll) 1e18 + 1e9 + 123;

#define rep(i, s, t) for (auto i = (s); i < (t); ++(i))
#define per(i, s, t) for (auto i = (s); i >= (t); --(i))
#define sz(x) ((int)(x).size())
#define all(x) (x).begin(), (x).end()
#define mp make_pair
#define pb push_back

bool mini(auto &x, const auto &y) {
    if (y < x) {
        x = y;
        return 1;
    }
    return 0;
}

bool maxi(auto &x, const auto &y) {
    if (y > x) {
        x = y;
        return 1;
    }
    return 0;
}

void run();

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    run();
    return 0;
}

const ll MOD = (ll) 1e9 + 7;

ll power(ll x, ll y) {
    if (y == 0) {
        return 1;
    }
    if (y % 2 == 0) {
        ll t = power(x, y / 2);
        return t * t % MOD;
    } else {
        return power(x, y - 1) * x % MOD;
    }
}

const int N = 3003;

int H, W;
ll f[N];
ll fact[N], rfact[N];

ll cnk(int n, int k) {
    return fact[n] * rfact[n - k] % MOD * rfact[k] % MOD;
}

ll calc2(int w, int h) {
    if ((w + h) % 3 != 0) {
        return 0;
    }
    int x = w - (w + h) / 3;
    int y = (w + h) / 3 - x;
    if (x < 0 || y < 0) {
        return 0;
    }
    ll res = cnk(w, y) * cnk(h, x) % MOD;
    res = res * f[x] % MOD;
    res = res * f[y] % MOD;
    return res;
}

ll calc1(int w, int h) {
    if (w < h) {
        swap(w, h);
    }
    return (cnk(w, h) * fact[h] % MOD * (power(5, h) + MOD - 1) % MOD + 1) % MOD;
}

void run() {
    f[0] = 1;
    rep(i, 1, N) {
        f[i] = i * 1LL * (2 * i - 1) * f[i - 1] % MOD;
    }
    fact[0] = 1;
    rep(i, 1, N) {
        fact[i] = fact[i - 1] * i % MOD;
    }
    rep(i, 0, N) {
        rfact[i] = power(fact[i], MOD - 2);
    }
    
    ll ans = MOD - 1;
    
    cin >> H >> W;
    rep(h, 0, H + 1) {
        rep(w, 0, W + 1) {
            ll cur = calc2(w, h) * calc1(W - w, H - h) % MOD;
            ans = (ans + cur) % MOD;
        }
    }
    
    cout << ans << "\n";
}

• Subtask 1: 0 / 48
• Subtask 2: 0 / 52