I have the following problem to solve:
Given a non-empty array A consisting of N integers, the task is to find the first unique number in the array. A unique number is defined as a number that occurs exactly once in the array. The desired output is the unique number with the lowest position in the array.
For example, consider the following array A:
A = 4 A = 10 A = 5 A = 4 A = 2 A = 10
In this array, the unique numbers are 5 and 2. The first unique number with the lowest position is 5 because A = 5.
The problem requires an algorithm and the time complexity for finding the first unique number in the given array. The algorithm should be able to handle a generic case where the given array A can have any size N and any set of integers.