Help me for this assignment please!?

Given an array of 2N+1 elements, N elements occur twice in the array. Find the element that occurs in the array only once.
You are expected to complete the function getUniqueElement(), 
which takes the array as a parameter and return the unique element present in it.
Constraints:
0 ? N ? 100000 and each element would range between 0 to 10^9
Sample Test Cases:

Input #00:
1 4 2 2 3 3 1

Output #00:
4

Explanation:
In the given array only 4 doesn't occur twice.