Submission #917650

#	Time	Username	Problem	Language	Result	Execution time	Memory
917650		VMaksimoski008	Network (BOI15_net)	C++17	100 / 100	457 ms	47820 KiB

net

#include <bits/stdc++.h>

#define pb push_back
#define eb emplace_back
#define sz(x) (int)x.size()
#define all(x) x.begin(), x.end()
#define uniq(x) x.erase(unique(all(x)), x.end())
#define rall(x) x.rbegin(), x.rend()
//#define int long long

using namespace std;

using ll = long long;
using ull = unsigned long long;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;

const int mod = 1e9 + 7;
const int LOG = 20;
const int maxn = 1e5 + 5;
const double eps = 1e-9;

void setIO() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
}

int n;
vector<vector<int> > graph;
vector<int> leaves;

void dfs(int u, int p) {
    for(int &v : graph[u]) {
        if(v == p) continue;
        dfs(v, u);
    }

    if(graph[u].size() == 1) leaves.push_back(u);
}

int32_t main() {
    setIO();

    cin >> n;
    graph.resize(n+1);

    for(int i=0; i<n-1; i++) {
        int a, b;
        cin >> a >> b;
        graph[a].push_back(b);
        graph[b].push_back(a);
    }

    dfs(1, 0);

    cout << (sz(leaves) + 1) / 2 << '\n';
    for(int i=0; i<sz(leaves)/2; i++)
        cout << leaves[i] << " " << leaves[i+sz(leaves)/2] << '\n';
    if(sz(leaves) % 2 == 1) cout << leaves[0] << " " << leaves.back() << '\n';
    return 0;
}

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