111. Find Unique Number in Array with Duplicates (Except One)

Objective: - Given an Integer array. An array contains duplicates of all the numbers in the array except for one number. Find that number.

Example :

int [] A = { 2,1,3,5,5,3,2,1,6,7,7,8,8};
Output: Missing duplicate is 6

Approach:

The naive solution is to use map or dictionary (Space complexity - O(n))
Better solution - XOR
A^A = 0 and A^B^A = B, so if we XOR all the elements, the answer will be the missing number.
If we have only one element, the missing no will be that no

Output:

Missing duplicate is 6