Submission #499900

#	Time	Username	Problem	Language	Result	Execution time	Memory
499900		SirCovidThe19th	Network (BOI15_net)	C++17	100 / 100	642 ms	47716 KiB

net

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

int n; vector<int> adj[500005], leaf;

void dfs(int cur, int p){
    if (adj[cur].size() == 1) leaf.push_back(cur);
    for (int nxt : adj[cur]) if (nxt != p) dfs(nxt, cur);
}

int main(){
    cin >> n;
    for (int i = 1; i < n; i++){
        int a, b; cin >> a >> b;
        adj[a].push_back(b); adj[b].push_back(a);
    }
    dfs(1, 0);
    int sz = leaf.size();
    cout<<(sz + 1) / 2<<"\n";
    for (int i = 0; i + sz / 2 < sz; i++) cout<<leaf[i]<<" "<<leaf[i + sz / 2]<<"\n";
}

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