Submission #311451

#	Time	Username	Problem	Language	Result	Execution time	Memory
311451		sofapuden	Network (BOI15_net)	C++14	100 / 100	1056 ms	60012 KiB

net

#include <bits/stdc++.h>

using namespace std;

vector<vector<int>> v;
vector<int> o;
vector<int> lea;

void dfs(int x, int p){
	for(int y : v[x]){
		if(y == p)continue;
		dfs(y,x);
	}
	o.push_back(x);
}

int main(){
	int n; cin >> n;
	v.resize(n);
	for(int i = 0; i < n-1; ++i){
		int a, b; cin >> a >> b;
		a--, b--;
		v[a].push_back(b);
		v[b].push_back(a);
	}
	int root = 0;
	for(int i = 0; i < n; ++i){
		if(v[i].size() >= 2)root = i;
	}
	dfs(root,root);
	for(int x : o){
		if(v[x].size() == 1)lea.push_back(x);
	}
	int ln = lea.size();
	cout << (ln+1)/2 << "\n";
	for(int i = 0; i < ln/2; ++i){
		cout << lea[i]+1 << " " << lea[(ln+1)/2+i]+1 << "\n";
	}
	if(ln&1){
		cout << root+1 << " " << lea[ln/2]+1 << "\n";
	}
		
}
		

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