Submission #823021

#	Time	Username	Problem	Language	Result	Execution time	Memory
823021		serifefedartar	Network (BOI15_net)	C++17	100 / 100	371 ms	47664 KiB

net

#include <bits/stdc++.h>
using namespace std;
 
#define fast ios::sync_with_stdio(0);cin.tie(0);
typedef long long ll;
#define f first
#define s second
#define MOD 1000000009
#define LOGN 20
#define MAXN 2000100
 
vector<vector<int>> graph;
vector<int> leaves;
void dfs(int node, int parent) {
    if (graph[node].size() == 1)
        leaves.push_back(node);

    for (auto u : graph[node]) {
        if (u == parent)
            continue;
        dfs(u, node);
    }
}

int main() {
    fast
    int n, u, v;
    cin >> n;

    graph = vector<vector<int>>(n+1, vector<int>());
    for (int i = 1; i < n; i++) {
        cin >> u >> v;
        graph[u].push_back(v);
        graph[v].push_back(u);
    }
    dfs(1, 1);

    cout << (leaves.size()+1) / 2 << "\n";
    for (int i = 0; i < (leaves.size()+1)/2; i++) {
        cout << leaves[i] << " " << leaves[i + leaves.size()/2] << "\n";       
    }
}

Compilation message (stderr)

net.cpp: In function 'int main()':
net.cpp:39:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   39 |     for (int i = 0; i < (leaves.size()+1)/2; i++) {
      |                     ~~^~~~~~~~~~~~~~~~~~~~~

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