Submission #169006

#	Time	Username	Problem	Language	Result	Execution time	Memory
169006		_qVp_	Network (BOI15_net)	C++14	0 / 100	23 ms	23800 KiB

net

#include <bits/stdc++.h>

using namespace std;

const int md = 1e6 + 10;

vector < int > adj[md];
vector < int > leaves;
int n;

void dfs(int u, int par) {
    if (adj[u].size() == 1)
        leaves.push_back(u);
    for(auto v : adj[u]) {
        if (v != par)
            dfs(v, u);
    }
}

int main() {
    //freopen("test.in", "r", stdin);
    ios_base::sync_with_stdio(0);
    cin >> n;
    for(int i = 1; i < n; i++) {
        int u, v;
        cin >> u >> v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }
    leaves.push_back(0);
    dfs(1, -1);
    int len = leaves.size() - 1;
    cout << (len + 1) / 2 << '\n';
    for(int i = 1; i <= len / 2; i++) 
        cout << leaves[i] << " " << leaves[len - i + 1] << '\n';
    if (len & 1)
        cout << leaves[len / 2] << " " << leaves[len / 2 + 1];
    return 0;
}

• Subtask 1: 0 / 18
• Subtask 2: 0 / 45
• Subtask 3: 0 / 37