# LeetCode 448. Find All Numbers Disappeared in an Array

## Description

https://leetcode.com/problems/find-all-numbers-disappeared-in-an-array/

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: 
```

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.

## Explanation

Find the length of nums list and check which number is missing in the list number range.

## Python Solution

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

n = len(nums)

nums = set(nums)

results = []
for i in range(1, n + 1):
if i not in nums:
results.append(i)

return results``````
• Time Complexity: O(N).
• Space Complexity: O(N).