Submission #165591

#	Time	Username	Problem	Language	Result	Execution time	Memory
165591		jovan_b	Tents (JOI18_tents)	C++17	48 / 100	2061 ms	28040 KiB

tents

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

const int MOD = 1000000007;

typedef long long ll;

int add(int a, int b){
    return (a+b)%MOD;
}

int mul(int a, int b){
    return ((ll)a*b)%MOD;
}

int pw(int a, int b){
    if(b == 0) return 1;
    int res = pw(a, b/2);
    res = mul(res, res);
    if(b%2) res = mul(res, a);
    return res;
}

int inv[3005];
int fact[3005];

int bin(int n, int k){
    if(n < 0 || k < 0 || n < k) return 0;
    int res = fact[n];
    res = mul(res, inv[n-k]);
    res = mul(res, inv[k]);
    return res;
}

int brackets[3005][3005];

int main(){
    ios_base::sync_with_stdio(false);

    fact[0] = inv[0] = 1;
    for(int i=1; i<=3000; i++){
        fact[i] = mul(fact[i-1], i);
        inv[i] = pw(fact[i], MOD-2);
    }
    brackets[0][0] = 1;
    for(int i=0; i<3000; i++){
        for(int j=0; j<=i; j++){
            brackets[i+1][j+1] = add(brackets[i+1][j+1], brackets[i][j]);
            if(j) brackets[i+1][j-1] = add(brackets[i+1][j-1], mul(j, brackets[i][j]));
        }
    }
    int h, w;
    cin >> h >> w;
    int res = 0;
    //cout << brackets[4][0] << "eee";
    for(int i=0; i<=h && 2*i<=w; i++){
        for(int j=0; j+2*i<=w && 2*j+i<=h; j++){
            /// i = broj hor. parova
            /// j = broj ver. parova
            int tren = 1;
            /// hor. parovi
            tren = mul(tren, bin(h, i));
            tren = mul(tren, fact[i]);
            tren = mul(tren, bin(w, 2*i));
            tren = mul(tren, brackets[2*i][0]);
            /// ver. parovi
            /// ostalo je h-i redova i w-2*i kolona
            tren = mul(tren, bin(w-2*i, j));
            tren = mul(tren, fact[j]);
            tren = mul(tren, bin(h-i, 2*j));
            tren = mul(tren, brackets[2*j][0]);
            /// sami
            /// ostalo je h-i-2*j redova i w-2*i-j kolona
            int h1 = h-i-2*j, w1 = w-2*i-j;
            int g = 0;
            tren = mul(tren, fact[w1]);
            tren = mul(tren, fact[h1]);
            for(int k=0; k<=min(h1, w1); k++){
                if(i+j+k == 0) continue;
                int t2 = 1;
                t2 = mul(t2, pw(4, k));
                t2 = mul(t2, inv[k]);
                t2 = mul(t2, inv[h1-k]);
                t2 = mul(t2, inv[w1-k]);
                g = add(g, t2);
            }
            res = add(res, mul(tren, g));
        }
    }
    cout << res;
    return 0;
}

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