[Solved] Given an array nums of n integers where nums[i] is in the range [1, n], return an array of all the integers in the range [1, n] that do not appear in nums.

Question

Given an array nums of n integers where nums[i] is in the range [1, n], return an array of all the integers in the range [1, n] that do not appear in nums.

Example 1:

Input: nums = [4,3,2,7,8,2,3,1]
Output: [5,6]

Example 2:

Input: nums = [1,1]
Output: [2]

Constraints:

• n == nums.length
• 1 <= n <= 105
• 1 <= nums[i] <= n

Follow up: Could you do it without extra space and in O(n) runtime? You may assume the returned list does not count as extra space.

Python Solution

class Solution:
    def findDisappearedNumbers(self, nums: List[int]) -> List[int]:

        for i in nums:
            if nums[abs(i)-1]>0:
                nums[abs(i)-1]*=-1
                
        return [i + 1 for i in range(len(nums)) if nums[i] > 0]