Leetcode 448 Find All Numbers Disappeared in an Array

        for all numbers in array
            Each number is treated as index (-1)
            Mark that "index" in the array as "seen" (add a -)
        Any positive indexes left will be numbers missing

class Solution:
    def findDisappearedNumbers(self, nums: List[int]) -> List[int]:
        # Alternative Solution 1:
        #   Generate hashmap of 1..n
        #   Mark each number in hashmap as "seen"
        #   Find values in hashmap that are 0 and return it
        # Time Complexity: O(n)
        # Space Complexity: O(n)

        # Alternative Solution 2:
        #   Sort list O(n log n)
        #   check index + 1 = cur if not then it missing
        # Time Complexity: O(n log n)
        # Space Complexity: O(n)

        for i, num in enumerate(nums):
            # real index num - 1
            rIndex = abs(num) - 1
            # Take the value at that index and make it negative
            nums[rIndex] = abs(nums[rIndex]) * -1

        return_list = []
        # Any numbers that are positive add index + 1 them return list
        for i,num in enumerate(nums):
            if num > 0:
                return_list.append(i + 1)

        return return_list