제출 #990720

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
990720		Khanhcsp2	Network (BOI15_net)	C++14	100 / 100	198 ms	57684 KiB

net

#include <bits/stdc++.h>
#define el '\n'
#define fi first
#define sc second
#define int ll
#define pii pair<int, int>
#define all(v) v.begin(), v.end()
using namespace std;
using ll=long long;
using ull=unsigned long long;
using ld=long double;
const int mod=1e9+7;
const int N=5e5+11;
int n, root;
vector<int> adj[N], leaf;
void dfs(int u, int pa)
{
    if(adj[u].size()==1) leaf.push_back(u);
    for(int v:adj[u])
    {
        if(v!=pa) dfs(v, u);
    }
}
void sol()
{
    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);
    }
    for(int i=1;i<=n;i++) if(adj[i].size()>1) root=i;
    dfs(root, 0);
    int sz=leaf.size();
    cout << (sz+1)/2 << el;
    for(int i=0; i<(sz+1)/2; i++) cout << leaf[i] << ' ' << leaf[i + sz / 2] << el;
}
signed main()
{
//    freopen("divisor.INP", "r", stdin);
//    freopen("divisor.OUT", "w", stdout);
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    int t=1;
    //cin >> t;
    while(t--)
    {
        sol();
    }
}

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