Submission #394455

#	Time	Username	Problem	Language	Result	Execution time	Memory
394455		Alma	Network (BOI15_net)	C++14	100 / 100	487 ms	51944 KiB

net

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

vector<int> a;

void f (int p, int n, vector<vector<int>> & g) {
    if ((int)g[n].size() == 1) a.push_back(n);
    for (int c: g[n]) {
        if (c != p) f (n, c, g);
    }
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(NULL); cout.tie(NULL);
    int n, u, v, s;
    cin >> n;
    vector<vector<int>> g(n, vector<int>());
    for (int i = 0; i < n-1; i++) {
        cin >> u >> v;
        u--; v--;
        g[u].push_back(v);
        g[v].push_back(u);
    }
    f (-1, 0, g);
    cout << ((int)a.size() + 1) / 2 << '\n';
    s = (int)a.size() / 2;
    for (int i = 0; i < s; i++) {
        cout << a[i] + 1 << ' ' << a[s+i] + 1 << '\n';
    }
    s = (int)a.size();
    if (s % 2 == 1) cout << a[0] + 1 << ' ' << a[s-1] + 1 << '\n';
    return 0;
}

• Subtask 1: 18 / 18
• Subtask 2: 45 / 45
• Subtask 3: 37 / 37