View Code of Problem 3929

#include<iostream>
#include<vector>
#include<algorithm>
#include<iomanip>
#include<string>
#include<cmath>
#include<unordered_map>
#include<stack>

using namespace std;


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

	for (int i = 0; i < T; i++) {

		int n;
		cin >> n;

		unordered_map<int, int> map;

		for (int j = 0; j < n; j++) {

			int temp;
			cin >> temp;
			map[temp]++;
		}

		int sum = 0;
		for (auto item : map) {

			if (item.second % 2 != 0)
				sum = sum ^ item.first;
		}

		cout << sum << endl;
	}
}