Submission #900115

#	Time	Username	Problem	Language	Result	Execution time	Memory
900115		LCJLY	Network (BOI15_net)	C++14	100 / 100	345 ms	48592 KiB

net

#include <bits/stdc++.h>
using namespace std;

#define int long long
#define ld long double
#define show(x,y) cout << y << " " << #x << endl;
#define show2(x,y,i,j) cout << y << " " << #x << "  " << j << " " << #i << endl;
#define show3(x,y,i,j,p,q) cout << y << " " << #x << "  " << j << " " << #i << "  " << q << " " << #p << endl; 
#define show4(x,y) for(auto it:x) cout << it << " "; cout << #y << endl;
typedef pair<long long,long long>pii;
typedef pair<pii,pii>pi2;

vector<int>adj[500005];
vector<int>leaf;

void dfs(int index, int par){
	if(adj[index].size()==1)leaf.push_back(index);
	
	for(auto it:adj[index]){
		if(it==par) continue;
		dfs(it,index);
	}
}

void solve(){	
	int n;
	cin >> n;
	
	int temp,temp2;
	for(int x=0;x<n-1;x++){
		cin >> temp >> temp2;
		adj[temp].push_back(temp2);
		adj[temp2].push_back(temp);
	}
	
	for(int x=1;x<=n;x++){
		if(adj[x].size()>1){
			dfs(x,-1);
			break;
		}
	}
	
	int sz=leaf.size();
	cout << (sz+1)/2 << "\n";
	for(int x=sz/2;x<sz;x++){
		cout << leaf[x] << " " << leaf[x-sz/2] << "\n";
	}
	cout << "\n";
	
	
}	

int32_t main(){										
	ios::sync_with_stdio(0);	
	cin.tie(0);
	int t=1;
	//cin >> t;
	while(t--){
		solve();
	}
}

		

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