[Leet Code] Kth Missing Positive Number

Leetcode: https://leetcode.com/problems/kth-missing-positive-number/

Problem:

Given an array arr of positive integers sorted in a strictly increasing order, and an integer k.

Find the kth positive integer that is missing from this array.

Example 1:

Input: arr = [2,3,4,7,11], k = 5
Output: 9
Explanation: The missing positive integers are [1,5,6,8,9,10,12,13,...]. The 5th missing positive integer is 9.

Example 2:

Input: arr = [1,2,3,4], k = 2
Output: 6
Explanation: The missing positive integers are [5,6,7,...]. The 2nd missing positive integer is 6.

Solution:

        counter = 0
        for i in range(1,10000):
            if i not in arr and counter == k-1:
                return i
            if i not in arr:
                counter += 1

The description in this doesn’t clearly tell us the upper bounds, but this is a very resource heavy bruteforce method of completing this task.