Submission #1179959

#	Time	Username	Problem	Language	Result	Execution time	Memory
1179959		nguyenkhangninh99	Network (BOI15_net)	C++20	0 / 100	11 ms	23880 KiB

net

#include <bits/stdc++.h>

using namespace std;

#define pii pair<int, int>
#define fi first
#define se second

const int maxn = 1e6 + 5;

vector<int> g[maxn];

void solve (){
    int n; cin >> n;

    for(int i = 1; i <= n - 1; i++){
        int u, v; cin >> u >> v;
        g[u].push_back(v);
        g[v].push_back(u);
    }
    int ans = 0;
    vector<int> v;

    for(int i = 1; i <= n; i++){
        if(g[i].size() == 1){
            ans++;
            v.push_back(i);
        }
    }

    cout << (ans + 1) / 2 << "\n";
    if(v.size() % 2 == 1) cout << 1 << " " << v.back() << "\n";
    for(int i = 0; i + 1 < v.size(); i += 2){
        cout << v[i] << " " << v[i + 1] << "\n";
    }

}

signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);

    solve();
}

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