class Solution:
  def findNumbers(self, nums):
    missing = []

    def swap(i, j):
      nums[i], nums[j] = nums[j], nums[i]
    
    for i in range(len(nums)):
      # nums[i] != nums[nums[i] - 1] = an item that is in the correctly positioned
      # while the item is miss positioned and not referring to an item that in the correctly positioned. keep swapping
      while nums[i] != i + 1 and nums[i] != nums[nums[i] - 1]:
        swap(i, nums[i] - 1)

    # like in 1, 2, 3, 1, 5, 3, 2, 8
    for i in range(len(nums)):
      if nums[i] != i + 1:
        missing.append(i + 1)
    
    return missing