Get the Next Small Integer in Python
The challenge
Write a function:
def solution(A)
that, given an array A of N integers, returns the smallest positive integer (greater than 0) that does not occur in A.
For example, given A = [1, 3, 6, 4, 1, 2]
, the function should return 5.
Given A = [1, 2, 3]
, the function should return 4.
Given A = [−1, −3]
, the function should return 1.
Write an efficient algorithm for the following assumptions:
 N is an integer within the range [1..100,000];
 each element of array A is an integer within the range [−1,000,000..1,000,000].
The solution

