Submission #873710

#	Time	Username	Problem	Language	Result	Execution time	Memory
873710		Pannda	Skyscraper (JOI16_skyscraper)	C++17	100 / 100	133 ms	5244 KiB

skyscraper

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

#define int long long

const int P = (int)1e9 + 7;

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int n, l;
    cin >> n >> l;
    vector<int> a(n);
    for (int i = 0; i < n; i++) {
        cin >> a[i];
    }
    sort(a.begin(), a.end());

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

    // (comp, cnt, sum): 'comp' components, 'cnt' bounding elements, total delta of 'sum' | after adding a[i]
    vector<vector<vector<int>>> prev(n + 1, vector<vector<int>>(3, vector<int>(l + 1, 0)));
    prev[1][0][0] = 1;
    prev[1][1][0] = 2;

    for (int i = 1; i < n; i++) {
        vector<vector<vector<int>>> dp(n + 1, vector<vector<int>>(3, vector<int>(l + 1, 0)));
        int d = a[i] - a[i - 1];
        for (int comp = 0; comp <= n; comp++) {
            for (int sum = 0; sum <= l; sum++) {
                // 0 bounding element
                if (sum + (2 * comp) * d <= l) {
                    if (comp + 1 <= n) (dp[comp + 1][0][sum + (2 * comp) * d] += (comp + 1) * prev[comp][0][sum]) %= P;
                    (dp[comp][0][sum + (2 * comp) * d] += (2 * comp) * prev[comp][0][sum]) %= P;
                    if (comp - 1 >= 0) (dp[comp - 1][0][sum + (2 * comp) * d] += (comp - 1) * prev[comp][0][sum]) %= P;
                }

                // 1 bounding element
                if (0 <= sum + (2 * comp - 1) * d && sum + (2 * comp - 1) * d <= l) {
                    if (comp + 1 <= n) (dp[comp + 1][1][sum + (2 * comp - 1) * d] += (comp) * prev[comp][1][sum]) %= P;
                    (dp[comp][1][sum + (2 * comp - 1) * d] += (2 * comp - 1) * prev[comp][1][sum]) %= P;
                    if (comp - 1 >= 0) (dp[comp - 1][1][sum + (2 * comp - 1) * d] += (comp - 1) * prev[comp][1][sum]) %= P;
                }
                if (sum + (2 * comp) * d <= l) {
                    if (comp + 1 <= n) (dp[comp + 1][1][sum + (2 * comp) * d] += 2 * prev[comp][0][sum]) %= P;
                    (dp[comp][1][sum + (2 * comp) * d] += 2 * prev[comp][0][sum]) %= P;
                }

                // 2 bounding elements
                if (0 <= sum + (2 * comp - 2) * d && sum + (2 * comp - 2) * d <= l) {
                    if (comp + 1 <= n) (dp[comp + 1][2][sum + (2 * comp - 2) * d] += (comp - 1) * prev[comp][2][sum]) %= P;
                    (dp[comp][2][sum + (2 * comp - 2) * d] += (2 * comp - 2) * prev[comp][2][sum]) %= P;
                    if (comp - 1 >= 0) (dp[comp - 1][2][sum + (2 * comp - 2) * d] += (comp - 1) * prev[comp][2][sum]) %= P;
                }
                if (0 <= sum + (2 * comp - 1) * d && sum + (2 * comp - 1) * d <= l) {
                    if (comp + 1 <= n) (dp[comp + 1][2][sum + (2 * comp - 1) * d] += prev[comp][1][sum]) %= P;
                    (dp[comp][2][sum + (2 * comp - 1) * d] += prev[comp][1][sum]) %= P;
                }
            }
        }
        swap(dp, prev);
    }

    cout << accumulate(prev[1][2].begin(), prev[1][2].end(), 0LL) % P << '\n';
}

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