Submission #356237

#	Time	Username	Problem	Language	Result	Execution time	Memory
356237		nikita4109	Network (BOI15_net)	C++17	0 / 100	10 ms	12140 KiB

net

#include <bits/stdc++.h>

using namespace std;

random_device rd;
mt19937 rnd(rd());
#define pt pair<int, int>
#define x first
#define y second
#define what_is(x) cerr << #x << " is " << x << endl;
#define ok cerr << "ok" << endl;
#define endl '\n'
#define int long long
#define ld long double

const int N = 5e5 + 5;

vector<int> g[N];

signed main()
{
	cin.tie(0), cout.tie(0), ios::sync_with_stdio(0);

	int n;
	cin >> n;
	for (int i = 0, x, y; i < n - 1; ++i)
	{
		cin >> x >> y;
		--x, --y;
		g[x].push_back(y);
		g[y].push_back(x);
	}

	vector<int> a;
	for (int i = 0; i < n; ++i)
	{
		assert((int)g[i].size() > 0);
		if (g[i].size() == 1)
			a.push_back(i + 1);
	}

	int len = a.size();
	if (len % 2)
	{
		cout << len / 2 + 1 << endl;
		cout << a[0] << " " << a.back();
		for (int i = 0; i < a.size() / 2; ++i)
			cout << a[i] << " " << a[i + a.size() / 2] << endl;
	}
	else
	{
		cout << len / 2 << endl;
		for (int i = 0; i < a.size() / 2; ++i)
			cout << a[i] << " " << a[i + a.size() / 2] << endl;
	}


	return 0;
}

Compilation message (stderr)

net.cpp: In function 'int main()':
net.cpp:47:21: 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]
   47 |   for (int i = 0; i < a.size() / 2; ++i)
      |                   ~~^~~~~~~~~~~~~~
net.cpp:53:21: 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]
   53 |   for (int i = 0; i < a.size() / 2; ++i)
      |                   ~~^~~~~~~~~~~~~~

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