Submission #677746

#	Time	Username	Problem	Language	Result	Execution time	Memory
677746		bashkort	Power Plant (JOI20_power)	C++17	100 / 100	186 ms	37188 KiB

power

#include <bits/stdc++.h>

using namespace std;
using ll = long long;

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

    int n;
    cin >> n;

    vector<vector<int>> adj(n);

    for (int i = 1; i < n; ++i) {
        int a, b;
        cin >> a >> b;
        --a, --b;

        adj[a].push_back(b);
        adj[b].push_back(a);
    }

    string str;
    cin >> str;

    vector<bool> active(n);
    for (int i = 0; i < n; ++i) {
        active[i] = str[i] - '0';
    }

    if (active == vector(n, false)) {
        cout << 0 << '\n';
        return 0;
    }

    vector<int> dp(n);

    function<void(int, int)> dfs = [&](int v, int p) {
        for (int to : adj[v]) {
            if (to != p) {
                dfs(to, v);
                dp[v] += dp[to];
            }
        }
        dp[v] -= active[v];

        if (active[v]) {
            dp[v] = max(dp[v], 1);
        }

        dp[v] = max(dp[v], 0);
    };
    dfs(0, -1);

    int ans = 1;
    function<void(int, int, int)> gfs = [&](int v, int p, int up) {
        int sum = 0;
        for (int to : adj[v]) {
            if (to != p) {
                sum += dp[to];
            }
        }
        ans = max(ans, sum + up - active[v]);
        sum = sum + up - active[v];
        for (int to : adj[v]) {
            if (to != p) {
                int k = max(sum - dp[to], int(active[v]));
                ans = max(ans, dp[to] + k);
                gfs(to, v, k);
            }
        }
    };
    gfs(0, -1, 0);

    cout << ans << '\n';

    return 0;
}

• Subtask 1: 6 / 6
• Subtask 2: 41 / 41
• Subtask 3: 53 / 53