# Solving Leetcode Interviews in Seconds with AI: Missing Number


	# Introduction
	In this blog post, we will explore how to solve the LeetCode problem "268" 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 containing n distinct numbers in the range [0, n], return the only number in the range that is missing from the array.   Example 1:  Input: nums = [3,0,1] Output: 2 Explanation: n = 3 since there are 3 numbers, so all numbers are in the range [0,3]. 2 is the missing number in the range since it does not appear in nums.  Example 2:  Input: nums = [0,1] Output: 2 Explanation: n = 2 since there are 2 numbers, so all numbers are in the range [0,2]. 2 is the missing number in the range since it does not appear in nums.  Example 3:  Input: nums = [9,6,4,2,3,5,7,0,1] Output: 8 Explanation: n = 9 since there are 9 numbers, so all numbers are in the range [0,9]. 8 is the missing number in the range since it does not appear in nums.                      Constraints:  n == nums.length 1 <= n <= 104 0 <= nums[i] <= n All the numbers of nums are unique.    Follow up: Could you implement a solution using only O(1) extra space complexity and O(n) runtime complexity? 

	# Explanation
	Here's a breakdown of the solution and the Python code:

*   **Approach:**
    *   Use the mathematical formula for the sum of an arithmetic series (sum of numbers from 0 to n).
    *   Calculate the expected sum (sum of 0 to n).
    *   Subtract the actual sum of the numbers in the input array from the expected sum. The result is the missing number.

*   **Complexity:** O(n) time complexity, O(1) space complexity.

	
	# Code
	```python
	def missingNumber(nums):
    """
    Finds the missing number in an array containing n distinct numbers in the range [0, n].

    Args:
        nums: A list of integers.

    Returns:
        The missing number in the range.
    """
    n = len(nums)
    expected_sum = n * (n + 1) // 2
    actual_sum = sum(nums)
    return expected_sum - actual_sum
	```