View Code of Problem 3929

#include<iostream>
#include<vector>
#include<algorithm> 
using namespace std;

int main() {
	int T;
	cin >> T;
	while (T--) {
		int n; cin >> n;
		vector<int> arr(n);
		while (n--)
			cin >> arr[n];
		sort(arr.begin(), arr.end());
		for(int i=0;i<arr.size()-1;i++)
			if (arr[i] == arr[i + 1]) {
				arr.erase(arr.begin() + i);
				arr.erase(arr.begin() + i);
				i--;
			}
		if (arr.empty())continue;
		int result = arr[0];
		for (int i = 1; i < arr.size(); i++) 
			result ^= arr[i];
		cout << result << endl;
		
	}
}