Find All Numbers Disappeared in an Array
Difficulty: Easy
Category: DSA
Topics: Array, Hash Table
Asked at: Amazon
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.