The elves are working on a system to verify children's gift lists 👧👦. However, some lists are incomplete and numbers are missing!
Your task is to write a function that, given an array of numbers, finds all the numbers that are missing between 1 and n (where n is the size of the array or the highest number in the array).
Keep in mind that:
- Numbers may appear more than once and others may be missing
- The array always contains positive integers
- Counting always starts from 1
findMissingNumbers([1, 2, 4, 6]) // Expected result: [3, 5]
findMissingNumbers([4, 8, 7, 2]) // Expected result: [1, 3, 5, 6]
findMissingNumbers([3, 2, 1, 1]) // Expected result: []
findMissingNumbers([5, 5, 5, 3, 3, 2, 1]) // Expected result: [4]