Tanssiaiset

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

int main () {
	cin >> n;
	for (int i=0; i<=(n/2); i++) {
		cin >> a >> b;
		p[i]={a, b};
		if (s.count(a)) {
			d[a]=i;
			e[a]=t[a];
}
		if (s.count(b)) {
			d[b]=i;
			e[b]=t[b];
}
		s.insert(a);
		s.insert(b);
		t[a]=i;
		t[b]=i;
}
	for (int i=0; i<n; i++) {
		if (d[i]) z.insert(d[i]);
		if (e[i]) z.insert(e[i]);
}
	for (int i=0; i<n; i++) {
		if (z.count(i)==2) cout << p[i].first << " "<< p[i].second;
}
}

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