# Solving Leetcode Interviews in Seconds with AI: Find All Numbers Disappeared in an Array


	# Introduction
	In this blog post, we will explore how to solve the LeetCode problem "448" using AI. LeetCode is a popular platform for preparing for coding interviews, and with the help of AI tools like [Chatmagic](https://www.chatmagic.app), we can generate solutions quickly and efficiently - helping you pass the interviews and get the job offer without having to study for months.

	# Problem Statement
	> 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. 

	# Explanation
	Here's the breakdown of the approach, complexities, and Python code:

*   **In-place Modification:** The core idea is to utilize the input array `nums` itself as a hash table. We iterate through the array. For each number `num`, we find its corresponding index (`num - 1`). We then negate the value at that index if it's positive. This marks the presence of the number `num` in the array.

*   **Identifying Missing Numbers:** After marking all present numbers by negating the values at corresponding indices, we iterate through the modified array. Any index `i` with a positive value indicates that the number `i + 1` is missing from the original array.

*   **Returning the Result:** We collect the missing numbers (`i + 1`) into a result list and return it.

*   **Complexity:** O(n) time complexity and O(1) extra space complexity (excluding the output list, as specified in the problem).

	
	# Code
	```python
	def findDisappearedNumbers(nums):
    """
    Finds all numbers that are missing from the range [1, n] in an array of n integers.

    Args:
        nums: A list of integers where nums[i] is in the range [1, n].

    Returns:
        A list of all integers in the range [1, n] that do not appear in nums.
    """
    n = len(nums)
    for num in nums:
        index = abs(num) - 1
        if nums[index] > 0:
            nums[index] *= -1

    result = []
    for i in range(n):
        if nums[i] > 0:
            result.append(i + 1)

    return result
	```