Submission #252223

#	Time	Username	Problem	Language	Result	Execution time	Memory
252223		Blagojce	Network (BOI15_net)	C++11	0 / 100	8 ms	12160 KiB

net

#include <bits/stdc++.h> 
#define fr(i, n, m) for(int i = (n); i < (m); i ++)
#define pb push_back
#define st first
#define nd second
#define pq priority_queue
#define all(x) begin(x), end(x)
#include <time.h>
#include <cmath>

using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int,int> pii;

const int i_inf = 1e9;
const ll inf = 1e18;
const ll mod = 1000000007;
const ld eps = 1e-13;
const ld pi  = 3.14159265359;
 
mt19937 _rand(time(NULL));
clock_t timer = clock();
const int mxn = 5e5;

int n;
vector<int> g[mxn];
vector<int> v;
void dfs(int u, int p){
	for(auto e : g[u]){
		if(e == p) continue;
		dfs(e, u);
	}
	if((int)g[u].size() == 1){
		v.pb(u);
	}
}

void solve(){
	cin >> n;
	fr(i, 0, n-1){
		int u, v;
		cin >> u >> v;
		
		--u, --v;
		g[u].pb(v);
		g[v].pb(u);
	}
	dfs(0, 0);
	vector<pii> ans;
	for(int i = 1; i < (int)v.size()-1; i += 2){
		ans.pb({v[i], v[i+1]});
	}
	ans.pb({v[0], v.back()});
	
	cout<<ans.size()<<endl;
	
	for(auto u : ans) cout<<u.st+1<<' '<<u.nd+1<<endl;
	
}

 
int main(){


	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	solve();
}

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