Problem Link - Bit Manipulation - Single Number

### Problem Statement

You are given an array A_1, A_2, \dots, A_N of length N. Each distinct element appears twice except for one. Find that single one.

### Approach

The code uses the **XOR** operation to identify the unique element in the array, leveraging these key properties:

**XOR of a number with itself is 0**: x⊕x=0.**XOR of a number with 0 is the number itself**: x⊕0=x.**XOR is commutative and associative**: The order does not affect the result.

By **XORing** all elements, pairs cancel each other out, leaving only the unique element.

### Time Complexity

O(N) - where N is the number of elements in the array.

### Space Complexity

O(1) - since we are using a constant amount of extra space.