# Single Number II

Posted: 14 Jan, 2021
Difficulty: Easy

## PROBLEM STATEMENT

#### You are given an arbitrary array ‘arr’ consisting of N non-negative integers, where every element appears thrice except one. You need to find the element that appears only once.

##### Input Format:
``````The first line of the input contains a single integer T, representing the number of test cases.

The first line of each test case consists of a single integer N, representing the number of elements in the given array.

The second line of each test case contains N space-separated integers, denoting the elements of the array.
``````
##### Output Format:
``````For each test case, print a single integer representing the element that appears only once in the array.
``````
##### Note:
``````You do not need to print anything. It has already been taken care of. Just implement the given function.
``````
##### Constraints:
``````1 <= T <= 100
4 <= N <= 10^4
0 <= arr[i] < 10^9
Time Limit: 1sec
``````
``````Try to solve this problem in O(N) time and O(1) space complexity.