Submission #242848

#	Time	Username	Problem	Language	Result	Execution time	Memory
242848		osaaateiasavtnl	Tents (JOI18_tents)	C++14	48 / 100	2085 ms	9984 KiB

tents

#include<bits/stdc++.h>
using namespace std;
#define int long long
#define ii pair <int, int>
#define app push_back
#define all(a) a.begin(), a.end()
#define bp __builtin_popcountll
#define ll long long
#define mp make_pair
#define f first
#define s second
#define Time (double)clock()/CLOCKS_PER_SEC

const int N = 6007, MOD = 1000 * 1000 * 1000 + 7;

int mod(int n) {
    n %= MOD;
    if (n < 0) return n + MOD;
    else return n;
}   
int fp(int a, int p) {
    int ans = 1, c = a;
    for (int i = 0; (1ll << i) <= p; ++i) {
        if ((p >> i) & 1) ans = mod(ans * c);
        c = mod(c * c);
    }   
    return ans;
}   
int dv(int a, int b) { return mod(a * fp(b, MOD - 2)); }
int f[N], inv[N];
void prec() {
    f[0] = 1;
    for (int i = 1; i < N; ++i)
        f[i] = mod(f[i - 1] * i);
    inv[N - 1] = fp(f[N - 1], MOD - 2);
    for (int i = N - 2; i >= 0; --i)
        inv[i] = mod(inv[i + 1] * (i + 1));
}
int C(int n, int k) {
    if (n < k)
        return 0;
    return mod(f[n] * mod(inv[k] * inv[n - k]));
}
void add(int &a, int b) { a = mod(a + b); } 

int one[N][N];
int par[N];

signed main() {
    #ifdef HOME
    freopen("input.txt", "r", stdin);
    #else
    #define endl '\n'
    ios_base::sync_with_stdio(0); cin.tie(0);
    #endif
    int n, m;
    cin >> n >> m;
    
    prec();

    for (int i = 0; i <= n; ++i) {
        for (int j = 0; j <= m; ++j) {
            for (int k = 0; k <= i && k <= j; ++k) {
                add(one[i][j], mod(C(i,k)*C(j,k))*mod(f[k]*fp(4,k)));
            }   
        }   
    }   

    par[0] = 1;
    for (int i = 2; i < N; i += 2)
        par[i] = mod(par[i-2]*(i-1));        

    int ans = 0;
    for (int hor = 0; hor <= n; ++hor) {
        for (int ver = 0; ver <= m; ++ver) {
            int rem_n = n - hor - 2 * ver;
            int rem_m = m - ver - 2 * hor;
            if (rem_n >= 0 && rem_m >= 0) {
                int fc = mod(C(n, rem_n) * C(m, rem_m));
                fc = mod(fc * mod(C(hor + 2 * ver, hor) * C(ver + 2 * hor, ver)));

                fc = mod(fc * par[2 * ver]);
                fc = mod(fc * par[2 * hor]);
                fc = mod(fc * f[ver]);
                fc = mod(fc * f[hor]);

                add(ans, one[rem_n][rem_m] * fc);
            }   
        }   
    }   
    cout << mod(ans-1) << endl;
}

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