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# 448. Find All Numbers Disappeared in an Array

## Easy

***

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:**

<pre><code>Input: nums = [4,3,2,7,8,2,3,1]
<strong>Output:
</strong> [5,6]
</code></pre>

**Example 2:**

<pre><code>Input: nums = [1,1]
<strong>Output:
</strong> [2]
</code></pre>

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**Constraints:**

* `n == nums.length`
* `1 <= n <= 105`
* `1 <= nums[i] <= n`

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**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.