제출 #404156

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
404156		SavicS	Network (BOI15_net)	C++14	0 / 100	1 ms	324 KiB

net

#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <bits/stdc++.h>

#define fi first
#define se second
#define pb push_back
#define sz(a) (int)a.size()
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define ff(i,a,b) for(int i=a;i<=b;i++)
#define fb(i,b,a) for(int i=b;i>=a;i--)

using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
typedef pair<int,int> pii;
const int maxn = 500005;
const int inf = 1e9 + 5;

template<typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

// os.order_of_key(k) the number of elements in the os less than k
// *os.find_by_order(k)  print the k-th smallest number in os(0-based)

int n;
int deg[maxn];

int main()
{
    ios::sync_with_stdio(false);
    cout.tie(nullptr);
    cin.tie(nullptr);
	cin >> n;
	ff(i,1,n - 1){
		int u, v;
		cin >> u >> v;
		deg[u] += 1, deg[v] += 1;
	}
	
	vector<int> res;
	ff(i,1,n)if(deg[i] == 1)res.pb(i);
	
	int len = (sz(res) + 1) / 2, add = sz(res) / 2;
	
	cout << len << endl;
	ff(i,0,len - 1)cout << res[i] << " " << res[i + add] << '\n';
	
    return 0;
}
/**



// probati bojenje sahovski ili slicno

**/

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