Love For The Twins

#include<bits/stdc++.h>
using namespace std;

int countFreq(int arr[], int n)
{
	unordered_map<int, int> freq;
	int count = 0;
	for (int i = 0; i < n; i++)
		freq[arr[i]]++;
	for (int i = 0; i < n; i++) {
		if (freq[arr[i]] != -1)
		{
			count += (2 * (freq[arr[i]] / 2));
			freq[arr[i]] = -1;
		}
	}
	return count;
}


int main() {
#ifndef ONLINE_JUDGE
	//get input from input1.txt
	freopen("input1.txt", "r", stdin);
	//write output in output1.txt
	freopen("output1.txt", "w", stdout);
#endif
	int t;
	cin >> t;
	while (t--) {
		int n;
		cin >> n;
		int arr[n];
		for (int i = 0; i < n; i++) {
			cin >> arr[i];
		}
		cout << countFreq(arr, n) << endl;
	}
	return 0;
}