Submission #488553

#	Time	Username	Problem	Language	Result	Execution time	Memory
488553		alextodoran	Power Plant (JOI20_power)	C++17	100 / 100	174 ms	25140 KiB

power

/**
 ____ ____ ____ ____ ____
||a |||t |||o |||d |||o ||
||__|||__|||__|||__|||__||
|/__\|/__\|/__\|/__\|/__\|

**/

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

const int N_MAX = 200000;

int N;

vector <int> adj[N_MAX + 2];

bool plant[N_MAX + 2];

int down[N_MAX + 2];
int sumDown[N_MAX + 2];

void dfsDown (int u, int parent = -1) {
    for (int v : adj[u]) {
        if (v != parent) {
            dfsDown(v, u);
            sumDown[u] += down[v];
        }
    }
    down[u] = sumDown[u];
    if (plant[u] == true) {
        down[u] = max(sumDown[u] - 1, 1);
    }
}

int up[N_MAX + 2];

void dfsUp (int u, int parent = -1) {
    if (parent != -1) {
        up[u] = up[parent] + sumDown[parent] - down[u];
        if (plant[parent] == true) {
            up[u] = max(up[u] - 1, 1);
        }
    }
    for (int v : adj[u]) {
        if (v != parent) {
            dfsUp(v, u);
        }
    }
}

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

    cin >> N;
    for (int i = 1; i <= N - 1; i++) {
        int u, v;
        cin >> u >> v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }

    string str;
    cin >> str;
    for (int u = 1; u <= N; u++) {
        plant[u] = (str[u - 1] == '1');
    }

    int cntPlants = 0;
    for (int u = 1; u <= N; u++) {
        cntPlants += plant[u];
    }

    dfsDown(1);
    dfsUp(1);

    int answer = min(cntPlants, 2);
    for (int u = 1; u <= N; u++) {
        int full = up[u] + sumDown[u];
        if (plant[u] == true) {
            full = max(full - 1, 1);
        }
        answer = max(answer, full);
    }

    cout << answer << "\n";

    return 0;
}

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