Tietoverkko

#include <iostream>
#include <utility>
#include <vector>

using namespace std;

int main()
{
	int n;
	cin >> n;

	vector< vector<int> > nodes;
	vector<int> c;
	vector<bool> been;

	nodes.resize(n);
	c.resize(n, 0);
	been.resize(n, false);

	for(int i = 0; i < n; i++)
	{
		int a, b;
		cin >> a >> b;
		a--; b--;

		nodes[a].push_back(b);
		nodes[b].push_back(a);

		c[a]++;
		c[b]++;
	}

	int ret = 0;

	for(int i = 0; i < n; i++)
	{
		if(c[i] > 1)
			continue;
		
		ret++;
		int p = nodes[i][0], pp = i;
		been[i] = true;

		while(nodes[p].size() == 2 && !been[p])
		{
			been[p] = true;
			for(int j = 0; j < 2; j++)
			{
				if(nodes[p][j] == pp)
					continue;

				pp = p;
				p = nodes[p][j];
			}

			ret++;
		}
	}

	cout << ret << endl;
}

Test 1

Group: 1

Verdict: WRONG ANSWER

Test 2

Group: 1

Verdict: WRONG ANSWER

Test 3

Group: 1

Verdict: WRONG ANSWER

Test 4

Group: 1

Verdict: WRONG ANSWER

Test 5

Group: 1

Verdict: ACCEPTED

Test 6

Group: 2

Verdict: WRONG ANSWER

Test 7

Group: 2

Verdict: WRONG ANSWER

Test 8

Group: 2

Verdict: WRONG ANSWER

Test 9

Group: 2

Verdict: WRONG ANSWER

Test 10

Group: 2

Verdict: ACCEPTED