View Code of Problem 3929

#include<iostream>
#include<string>
#include<algorithm>
#include<stack>
#include<vector>

using namespace std;

int main() {
	int t, n;
	cin >> t;
	while (t--)
	{
		cin >> n;
		vector<long long> arr;
		long long temp;
		for (int i = 0; i < n; i++)
		{
			cin >> temp;
			arr.push_back(temp);
		}
		sort(arr.begin(), arr.end());
		arr.push_back(-1);//末位添加-1，防止循环判断漏掉原本末位的数字
		int num = 1, sum = 0;
		for (int i = 0; i < arr.size()-1; i++)
		{
			if (arr[i] != arr[i+1])
			{
				if (num%2!=0)
					sum ^= arr[i];
				num = 1;
			}
			else
				num++;
		}
		cout << sum << endl;
	}
	return 0;
}