find-all-numbers-disappeared-in-an-array

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Description

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.

Solution(Python)

class Solution:
    def findDisappearedNumbers(self, nums: List[int]) -> List[int]:
        integers = set(i+1 for i in range(len(nums)))
        for num in nums:
            if num in integers:
                integers.remove(num)
        return list(integers)