Submission #605042

#	Time	Username	Problem	Language	Result	Execution time	Memory
605042		tamthegod	Network (BOI15_net)	C++14	0 / 100	16 ms	23864 KiB

net

#include<bits/stdc++.h>

#define int long long
#define pb push_back
#define fi first
#define se second
using namespace std;
using ll = long long;
using ld = long double;
using ull = unsigned long long;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const int maxN = 1e6 + 5;
const int mod = 1e9 + 7;
const ll oo = 1e18;
int n;
vector<int> adj[maxN];
void ReadInput()
{
    cin >> n;
    for(int i=1; i<n; i++)
    {
        int u, v;
        cin >> u >> v;
        adj[u].pb(v);
        adj[v].pb(u);
    }
}
void Solve()
{
    vector<int> leaf;
    for(int i=1; i<=n; i++)
    {
        if(adj[i].size() == 1) leaf.pb(i);
    }
    if(leaf.size() % 2 == 0)
    {
        cout << leaf.size() / 2 << '\n';
        for(int i=0; i<leaf.size(); i+=2) cout << leaf[i] << " " << leaf[i + 1] << '\n';
        return;
    }
    cout << leaf.size() / 2 + 1 << '\n';
    for(int i=0; i<leaf.size()-1; i+=2) cout << leaf[i] << " " << leaf[i + 1] << '\n';
    for(int i=1; i<=n; i++)
    {
        if(i != adj[leaf.back()][0])
        {
            cout << leaf.back() << " " << i;
            return;
        }
    }
}
int32_t main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    ReadInput();
    Solve();
}

Compilation message (stderr)

net.cpp: In function 'void Solve()':
net.cpp:38:23: 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]
   38 |         for(int i=0; i<leaf.size(); i+=2) cout << leaf[i] << " " << leaf[i + 1] << '\n';
      |                      ~^~~~~~~~~~~~
net.cpp:42:19: 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]
   42 |     for(int i=0; i<leaf.size()-1; i+=2) cout << leaf[i] << " " << leaf[i + 1] << '\n';
      |                  ~^~~~~~~~~~~~~~

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