Submission #397012

#	Time	Username	Problem	Language	Result	Execution time	Memory
397012		The_Blitz	Network (BOI15_net)	C++17	0 / 100	1 ms	304 KiB

net

// Restart
// += O(logn) ; + = O(n)
 
//#pragma GCC optimize("Ofast")
//#pragma GCC optimize("unroll-loops")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp> // Common file
#include <ext/pb_ds/tree_policy.hpp> // Including tree_order_statistics_node_update
 
#define fastio ios_base::sync_with_stdio(0);cin.tie(0)
#define fst first
#define snd second
#define all(x) (x).begin(), (x).end()
#define pb push_back
#define sz size()
#define FORN(i,j,n) for(int i=j; i<(int)n;i++) 
#define FOR(i,n) FORN(i,0,n)
#define FORIT(i,x) for( auto i = x.begin() ; i != x.end() ; i++ )
#define MOD 998244353LL
#define MOD1 1000000007LL
#define LIM 262150
#define ones(x) __builtin_popcount(x)
#define trace(x)    cerr << #x << ": " << x << endl;
#define trace2(x, y) cerr << #x << ": " << x << " | " << #y << ": " << y << endl;
#define trace3(x, y,z) cerr << #x << ": " << x << " | " << #y << ": " << y << " | " << #z << ": " << z << endl;
#define INF 1000000000
#define in(x)  cin>>x;
#define out(x) cout<<x;
#define MAXIMO 1LL<<60

#define loga2(x) __builtin_ctzll(x)
//SOLO PARA POTENCIAS DE 2
 
using namespace std;
using namespace __gnu_pbds;
 
typedef long long ll ;
typedef unsigned long long ull ;
typedef vector <int> vi;
typedef pair <int,int> ii;
typedef pair <int,ii> iii;
typedef vector <string> vs;
typedef vector <ii> vii;
typedef vector <iii> viii;
typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update> ordered_set;

int degree[500005] = {0};
int v[500005] = {0};
set<int> ans;

vi v1;
vi v2;
vi v3;

void go(){

	int n; cin>>n;
	
	for(int i=1; i<n;i++){
		int x, y; cin >> x >> y;
		v[x] = y;
		v[y] = x;
		degree[x]++;
		degree[y]++;
	}

	for(int i=1; i<=n;i++){
		if(degree[i] == 1) ans.insert(i);
	}

	cout<< (ans.size() + 1)/2 <<"\n";
	
	for(int i=1; i<=n;i++){
		if(ans.count(i)){
			if(degree[i] == 1 && degree[v[i]] == 1){
				v1.pb(i); v2.pb(v[i]);
				ans.erase(v[i]);
			}
			else v3.pb(i);
			ans.erase(i);
		}
	}

	for( int i =0 ; i<v1.size() ; i++){
		swap(v3[i], v2[i]);
		cout<<v1[i]<<" "<<v2[i] << "\n";
	}

	for( int i =0 ; i<(v3.size() + 1)/2 ; i++){
		cout<<v3[i]<<" "<<v3[i + v3.size()/2] << "\n";
	}

}


void timer(){
	clock_t begin = clock();
	go();
	clock_t end = clock();
	double time_spent = (double)(end - begin) / CLOCKS_PER_SEC;
	cout<<time_spent<<"\n";
}	

 
int main() {
  //fastio;
  go();
  //timer();
  return 0;
}

Compilation message (stderr)

net.cpp: In function 'void go()':
net.cpp:85:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   85 |  for( int i =0 ; i<v1.size() ; i++){
      |                  ~^~~~~~~~~~
net.cpp:90:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   90 |  for( int i =0 ; i<(v3.size() + 1)/2 ; i++){
      |                  ~^~~~~~~~~~~~~~~~~~

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