View Code of Problem 3929

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

using namespace std;

//根据性质(a^b)^c == a^(b^c)、x^x=0和x^0=x可知，异或和会自动除去出现次数为偶数的数字，保留出现次数为奇数的数字
//故无需利用数组存储数字计算各数字出现的次数

int main() {
	int t, n;
	cin >> t;
	while (t--)
	{
		int sum = 0, temp;
		cin >> n;
		for (int i = 0; i < n; i++)
		{
			cin >> temp;
			sum ^= temp;
		}
		cout << sum << endl;
	}
	return 0;
}