Submission #1092989

#	Time	Username	Problem	Language	Result	Execution time	Memory
1092989		Zero_OP	Skyscraper (JOI16_skyscraper)	C++14	100 / 100	47 ms	16780 KiB

skyscraper

#include "bits/stdc++.h"

using namespace std;

const int mod = 1e9 + 7;
const int MAX = 1e3 + 5;

void add(int& a, int b){
    a += b;
    if(a >= mod) a -= mod;
}

int mul(int a, int b){
    return 1LL * a * b % mod;
}

int n, L, a[MAX], dp[101][101][1001][3];

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

    cin >> n >> L;
    for(int i = 1; i <= n; ++i){
        cin >> a[i];
    }

    if(n == 1){
        cout << 1 << '\n';
        return 0;
    }

    sort(a + 1, a + n + 1);

    dp[1][1][0][0] = 1;
    dp[1][1][0][1] = 2;

    for(int i = 1; i < n; ++i){
        for(int j = 1; j <= i; ++j){
            for(int k = 0; k <= L; ++k){
                for(int l = 0; l < 3; ++l){
                    int& ret = dp[i][j][k][l];
                    if(!ret) continue;

                    int sum = k + (2 * j - l) * (a[i + 1] - a[i]);
                    if((2 * j - l) < 0 || sum > L) continue;

                    add(dp[i + 1][j + 1][sum][l], mul(ret, j + 1 - l));
                    if(l < 2) add(dp[i + 1][j + 1][sum][l + 1], mul(ret, 2 - l));

                    add(dp[i + 1][j][sum][l], mul(ret, 2 * j - l));
                    if(l < 2) add(dp[i + 1][j][sum][l + 1], mul(ret, 2 - l));

                    if(j > 0) add(dp[i + 1][j - 1][sum][l], mul(ret, j - 1));
                }
            }
        }
    }

    int res = 0;
    for(int i = 0; i <= L; ++i){
        add(res, dp[n][1][i][2]);
    }

    cout << res << '\n';

    return 0;
}

• Subtask 1: 5 / 5
• Subtask 2: 15 / 15
• Subtask 3: 80 / 80