Find Duplicate in Array Problem Statement

You are provided with an array of integers 'ARR' consisting of 'N' elements. Each integer is within the range [1, N-1], and the array contains exactly one duplicated element.

Your task is to identify the duplicated element.

Example:

Input:

ARR = [3, 1, 3, 4, 2]

Output:

3

Explanation:

The element 3 occurs more than once, hence it is the duplicate.

Constraints:

• 1 <= T <= 5
• 1 <= N <= 105
• 1 <= ARR[i] <= N - 1
• Time Limit: 1 sec

Input:

The first line of input contains an integer ‘T’ representing the number of test cases. 
For each test case, the first line includes an integer ‘N’ for the number of elements in the array. 
The following line for each test case contains ‘N’ space-separated integers representing elements of the array.

Output:

For each test case, print the duplicate element in the array.
Each test case's result should be on a new line.

Note:

You are not required to print anything, as that's handled already. Your task is to implement the function to return the answer.