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Submission #765436

# Submission time Handle Problem Language Result Execution time Memory
765436 2023-06-24T13:25:18 Z vjudge1 Network (BOI15_net) C++17
0 / 100
 6 ms 12072 KB 
#include <bits/stdc++.h>
#define int long long
#define ull unsigned long long
#define mps make_pair
#define pb push_back
#define pf push_front
#define F first
#define S second
#define sz(x) (x).size() 
#define all(x) (x).begin(), (x).end()
#define booster ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define fopen(s) freopen(s".in","r",stdin);freopen(s".out","w",stdout)
 
using namespace std;

const int N = 5e5 + 123;

vector <int> g[N],vec;

bool used[N];

int n;

void dfs(int v){
	used[v] = true;

	if(sz(g[v]) == 1){
		vec.pb(v);
	}

	for(auto i : g[v]){
		if(!used[i]){
			dfs(i);
		}
	}
}

signed main()
{ 
	booster

	cin >> n;

	for(int i = 1; i <= n - 1; i++){
		int x,y;
		cin >> x >> y;

		g[x].pb(y);
		g[y].pb(x);
	}

	for(int i = 1; i <= n; i++){
		if(sz(g[i]) != 1){
			dfs(i);
			break;
		}
	}

	vector <pair<int,int>> pr;

	for(int i = 0; i < sz(vec) / 2; i++){
		pr.pb(mps(vec[i], vec[i + sz(vec) / 2]));
	}

	if(sz(vec) % 2 == 1){
		for(auto i : g[vec[sz(vec) - 1]]){
			if(i != 1){
				pr.pb(mps(vec[sz(vec) - 1], 1));
			}
			else {
				pr.pb(mps(vec[sz(vec) - 1], 2));
			}
		}
	}

	cout << sz(pr) << '\n';

	for(auto i : pr){
		cout << i.F << ' ' << i.S << '\n';
	}

	return 0;
}

/*
1 2 3 4 5 
0 1 2 3 4
*/

Compilation message

net.cpp: In function 'int main()':
net.cpp:61:19: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   61 |  for(int i = 0; i < sz(vec) / 2; i++){
      |                 ~~^~~~~~~~~~~~~

Subtask #1
0 / 18.0

# Verdict Execution time Memory Grader output
1 Correct 5 ms 11988 KB Output is correct
2 Correct 5 ms 12072 KB Output is correct
3 Correct 5 ms 11988 KB Output is correct
4 Correct 5 ms 11988 KB Output is correct
5 Correct 5 ms 11988 KB Output is correct
6 Correct 6 ms 11988 KB Output is correct
7 Incorrect 5 ms 11988 KB Breaking single line is causing network to disconnect.
8 Halted 0 ms 0 KB -

Subtask #2
0 / 45.0

# Verdict Execution time Memory Grader output
1 Correct 5 ms 11988 KB Output is correct
2 Correct 5 ms 12072 KB Output is correct
3 Correct 5 ms 11988 KB Output is correct
4 Correct 5 ms 11988 KB Output is correct
5 Correct 5 ms 11988 KB Output is correct
6 Correct 6 ms 11988 KB Output is correct
7 Incorrect 5 ms 11988 KB Breaking single line is causing network to disconnect.
8 Halted 0 ms 0 KB -

Subtask #3
0 / 37.0

# Verdict Execution time Memory Grader output
1 Correct 5 ms 11988 KB Output is correct
2 Correct 5 ms 12072 KB Output is correct
3 Correct 5 ms 11988 KB Output is correct
4 Correct 5 ms 11988 KB Output is correct
5 Correct 5 ms 11988 KB Output is correct
6 Correct 6 ms 11988 KB Output is correct
7 Incorrect 5 ms 11988 KB Breaking single line is causing network to disconnect.
8 Halted 0 ms 0 KB -