Submission #320884

#	Time	Username	Problem	Language	Result	Execution time	Memory
320884		gustason	Network (BOI15_net)	C++14	100 / 100	519 ms	52192 KiB

net

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int maxN = 500005;
vector<int> adj[maxN], leafs;
void dfs(int v, int par) {
    if (adj[v].size() == 1) {
        leafs.push_back(v);
    }
    for(int u : adj[v]) {
        if (u != par) {
            dfs(u, v);
        }
    }
}
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    int n;
    cin >> n;
    for(int i = 0; i < n-1; i++) {
        int a, b;
        cin >> a >> b;
        adj[a].push_back(b);
        adj[b].push_back(a);
    }

    dfs(1, -1);
    int ls = leafs.size();
    if (ls % 2 == 0) {
        cout << ls / 2 << "\n";
        for(int i = 0; i < ls/2; i++) {
            cout << leafs[i] << " " << leafs[ls/2+i] << "\n";
        }
    } else {
        cout << ls / 2 + 1 << "\n";
        for(int i = 0; i < ls/2; i++) {
            cout << leafs[i] << " " << leafs[ls/2+i] << "\n";
        }
        cout << leafs.back() << " " << leafs[ls/2];
    }
    return 0;
}
//~ check for overflows

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