Submission #380564

#	Time	Username	Problem	Language	Result	Execution time	Memory
380564		vishesh312	Network (BOI15_net)	C++17	100 / 100	518 ms	47888 KiB

net

#include "bits/stdc++.h"
using namespace std;
/*
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
using ordered_set = tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update>;
*/

#define all(x) begin(x), end(x)
#define sz(x) (int)x.size()

using ll = long long;
const int mod = 1e9+7;

vector<int> leaf;
vector<vector<int>> adj;

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

void solve(int tc) {
    int n;
    cin >> n;
    adj.resize(n);
    for (int i = 0; i < n-1; ++i) {
        int u, v;
        cin >> u >> v;
        --u, --v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }
    dfs(0, -1);
    cout << (sz(leaf)+1)/2 << '\n';
    for (int i = 0; i < sz(leaf)/2; ++i) {
        cout << leaf[i]+1 << " " << leaf[i+sz(leaf)/2]+1 << '\n';
    }
    if (sz(leaf)&1) cout << leaf[0]+1 << " " << leaf.back()+1 << '\n';
}

signed main() {
    ios_base::sync_with_stdio(false); cin.tie(NULL);
    int tc = 1;
    //cin >> tc;
    for (int i = 1; i <= tc; ++i) solve(i);
    return 0;
}

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