제출 #1174023

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
1174023		iamhereforfun	Network (BOI15_net)	C++20	100 / 100	337 ms	45304 KiB

net

// IamHereForFun //

#include <bits/stdc++.h>

using namespace std;

#define LSOne(S) ((S) & -(S))

const int N = 5e5 + 5;
const int Q = 2e5 + 5;
const int M = 1e6 + 5;
const int LG = 18;
const int P = 31;
const long long INF = 4e18;
const int MOD = 1e9;

int n, sz = 0;
vector<vector<int>> adj(N);
vector<int> leaves;

void setLeaves(int cur, int par)
{
    if (adj[cur].size() == 1)
    {
        leaves.push_back(cur);
    }
    for (int i : adj[cur])
    {
        if (i == par)
            continue;
        setLeaves(i, cur);
    }
}

void prtSolve()
{
    cin >> n;
    for (int x = 0; x < n - 1; x++)
    {
        int a, b;
        cin >> a >> b;
        adj[a].push_back(b);
        adj[b].push_back(a);
    }
    setLeaves(1, 0);
    sz = leaves.size();
    cout << (sz + 1) / 2 << "\n";
    for (int x = 0; x < sz / 2; x++)
    {
        cout << leaves[x] << " " << leaves[x + (sz + 1) / 2] << "\n";
    }
    if (sz % 2 == 1)
    {
        cout << 1 << " " << leaves[sz / 2] << "\n";
    }
}

signed main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int t = 1;
    // cin >> t;
    for (int x = 1; x <= t; x++)
    {
        prtSolve();
    }
    return 0;
}

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