Submission #286884

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Source Code Expand

#include <iostream>
#include <vector>

using namespace std;

class Solver {
    public:
        int n, x;
        int h[100], a[100], b[100];
        vector<int> next_nodes[100];
        int dfs(int current, int parent=-1) {
            int distance = 0;
            for (int i = 0; i < (int)next_nodes[current].size(); ++i) {
                int nn = next_nodes[current][i];
                if (nn != parent) {
                    int d = dfs(nn, current);
                    if (d > 0 || h[nn] > 0) {
                        distance += 1 + d;
                    }
                }
            }
            return distance;
        }
        int solve() {
            for (int i = 0; i < n; ++i) {
                next_nodes[i].clear();
            }
            for (int i = 0; i < n - 1; ++i) {
                next_nodes[a[i] - 1].push_back(b[i] - 1);
                next_nodes[b[i] - 1].push_back(a[i] - 1);
            }
            return dfs(x - 1) * 2;
        }
};

int main() {
    Solver s;
    cin >> s.n >> s.x;
    for (int i = 0; i < s.n; ++i) {
        cin >> s.h[i];
    }
    for (int i = 0; i < s.n - 1; ++i) {
        cin >> s.a[i] >> s.b[i];
    }
    cout << s.solve() << endl;
    return 0;
}

Submission Info

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