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

def solution(A):
    # sort the list and create a set
    # this will remove all duplicates
    A = set(sorted(A))
    
    # create the default answer of 1
    answer = 1
    
    # loop through all items in set
    for i in A:
        # if the same as answer
        if i == answer:
            # increment
            answer+=1
    
    
    # return the answer
    return answer
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