Find the element that appears once in sorted array

#include<bits/stdc++.h>
using namespace std;
int main()
{
	int t;
    scanf("%d",&t);
    while(t--){
        int n;
        cin >> n;
        int arr[n];
        for(int i=0;i<n;i++) cin >> arr[i];
        int x=arr[0];
        for(int i=1;i<n;i++){
            x=x^arr[i];
        }
        cout << x << endl;
    }
	return 0;
}