Missing Number Statement

Given an array ARR of integers with size N, where all elements appear an even number of times except for one element which appears an odd number of times, identify the element that appears an odd number of times.

Example:

Input:

N = 5
ARR = 1 2 3 2 3

Output:

1

Explanation:

All numbers occur an even number of times except for number 1.

Input:

The first line will contain an integer T, the number of test cases. For each test case, provide the following:
The first line contains a single integer, N, representing the size of the array.
The second line contains N space-separated integers representing the array elements.

Output:

For each test case, print a single integer indicating the number that appears an odd number of times.

Constraints:

• 1 <= T <= 10
• 1 <= N <= 10^4
• 1 <= ARR[i] <= 10^5
• Time Limit: 1 sec

Note:

You don't need to print anything, as it will be handled. Implement the function to determine the result.