Given an unsorted array of integers nums and a positive integer k, return the first `k` missing positive integers that are not present in nums.
The result should be returned in ascending order.
Example 1:
Input: nums = [3, -1, 4, 5, 5], k = 3
Output: [1, 2, 6]
Explanation: Missing positives in order: 1, 2, 6, 7... The first 3 are [1, 2, 6].
Example 2:
Input: nums = [2, 3, 4], k = 3
Output: [1, 5, 6]
Explanation: Missing positives: 1, 5, 6, 7... The first 3 are [1, 5, 6].
Example 3:
Input: nums = [1, 2, 3, 4], k = 2
Output: [5, 6]
Explanation: All of [1..4] are present, missing starts at 5.
1 <= nums.length <= 10^4-10^5 <= nums[i] <= 10^51 <= k <= 50