Tietoverkko

#include <bits/stdc++.h>
using namespace std;
int n, a, b, c, d, w;
vector<int> v[101010];
set<pair<int, int>> s;
int z[101010]={0};
int e[101010]={0};
int f[101010]={0};
pair <int, int> p;

void haku (int s, int r) {
	f[s]=r;
	if (z[s]) {
	e[s]=1;
	w=f[r];
	e[f[r]]=1;
	e[f[f[r]]]=1;
	e[f[f[f[r]]]]=1;
	while(s!=w) {
		w=f[w];
		e[w]=1;
}
	return;
}
	z[s]=1;
	
	for (auto u : v[s]) {
		if (u==r) continue;	
		
		haku(u, s);
	}
	
}

int main () {
	cin >> n;
	for (int i=0; i<n; i++) {
		cin >> a >> b;
		v[a].push_back(b);
		v[b].push_back(a);
		s.insert({a,b});
	}
	c=n;
	d=0;
	haku(1, 0);
	for (int i=1; i<=n; i++) {
		if (e[i]) c--;
}
	cout << c;
}

Test 1

Group: 1

Verdict: ACCEPTED

Test 2

Group: 1

Verdict: ACCEPTED

Test 3

Group: 1

Verdict: ACCEPTED

Test 4

Group: 1

Verdict: ACCEPTED

Test 5

Group: 1

Verdict: ACCEPTED

Test 6

Group: 2

Verdict: ACCEPTED

Test 7

Group: 2

Verdict: ACCEPTED

Test 8

Group: 2

Verdict: ACCEPTED

Test 9

Group: 2

Verdict: ACCEPTED

Test 10

Group: 2

Verdict: ACCEPTED