Submission #633953

#	Time	Username	Problem	Language	Result	Execution time	Memory
633953		MinaRagy06	Network (BOI15_net)	C++17	100 / 100	521 ms	56800 KiB

net

#include <bits/stdc++.h>
using namespace std;
#define lesgooo ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0)
#define endl    '\n'
#define int     long long

const int N = 5e5+5;
vector<int> adj[N], leaf;
void dfs(int i, int par)
{
    if (adj[i].size() == 1) return leaf.push_back(i), void();
    for (auto nxt : adj[i]) if (nxt != par) dfs(nxt, i);
}
int mx = 0, val = 0;
void dfs2(int i, int par, int sum)
{
    if (sum > mx) mx = sum ,val = i;
    for (auto nxt : adj[i]) if (nxt != par) dfs2(nxt, i, sum+1);
}
signed main()
{
    lesgooo;
    int n, u, v;
    cin >> n;
    for (int i =1 ; i < n; i++) cin >> u >> v, adj[--u].push_back(--v), adj[v].push_back(u);
    int mxx = 0, vall = 0;
    for (int i = 0; i < n; i++) if (adj[i].size() > mxx) mxx = adj[i].size(), vall = i;
    dfs(vall, -1);
    cout << (leaf.size()+1)/2 << endl;
    for (int i = 0; i < leaf.size()/2; i++) cout << leaf[i]+1 << " " << leaf[leaf.size()/2+i]+1 << endl;
    if (leaf.size()&1) dfs2(leaf.back(), -1, 0), cout << leaf.back()+1 << " " << val+1 << endl;
    return 0;
}

Compilation message (stderr)

net.cpp: In function 'int main()':
net.cpp:27:51: warning: comparison of integer expressions of different signedness: 'std::vector<long long int>::size_type' {aka 'long unsigned int'} and 'long long int' [-Wsign-compare]
   27 |     for (int i = 0; i < n; i++) if (adj[i].size() > mxx) mxx = adj[i].size(), vall = i;
      |                                     ~~~~~~~~~~~~~~^~~~~
net.cpp:30:23: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   30 |     for (int i = 0; i < leaf.size()/2; i++) cout << leaf[i]+1 << " " << leaf[leaf.size()/2+i]+1 << endl;
      |                     ~~^~~~~~~~~~~~~~~

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