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.
Constraints:
1 <= arr.length <= 10001 <= arr[i] <= 10001 <= k <= 1000arr[i] < arr[j] for 1 <= i < j <=
arr.length