Submission #1084973

#	Time	Username	Problem	Language	Result	Execution time	Memory
1084973		TheGreatAntivirus	Network (BOI15_net)	C++17	100 / 100	269 ms	48428 KiB

net

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define IOS ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define stdI freopen("input.txt", "r", stdin);
#define stdO freopen("output.txt", "w", stdout);
#define all(x) x.begin(), x.end()
#define mp(x, y) make_pair(x, y)
#define int long long
#define F first
#define S second
using namespace std;
using namespace __gnu_pbds;

typedef tree<int,
    null_type,less<int>,
    rb_tree_tag,
    tree_order_statistics_node_update> ordered_set;

typedef pair<int, int> pii;

const int MAXN = 5e5 + 100, INF = 1e18, MOD = 1e9 + 7;

vector<int> adj[MAXN];
vector<int> b;
int n;

void dfs(int v, int p)
{
    if(adj[v].size() == 1)
    {
        b.push_back(v);
    }
    for(auto u : adj[v])
    {
        if(u != p)
        {
            dfs(u, v);
        }
    }
}

void solve()
{
    cin >> n;
    for(int i = 1; i < n; i++)
    {
        int u, v; cin >> u >> v;
        adj[u].push_back(v); adj[v].push_back(u);
    }
    dfs(1, 0);
    if((b.size() & 1))
    {
        b.push_back(b[0]);
    }
    int nesf = b.size() / 2;
    cout << nesf << "\n";
    for(int i = 0; i < nesf; i++)
    {
        cout << b[i] << " " << b[nesf + i] << "\n";
    }
}

int32_t main()
{
    IOS;
    int t = 1;
    //cin >> t;
    while(t--)
    {
        solve();
    }
    return 0;
}

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