# Solving Leetcode Interviews in Seconds with AI: Single Number


	# Introduction
	In this blog post, we will explore how to solve the LeetCode problem "136" 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 a non-empty array of integers nums, every element appears twice except for one. Find that single one. You must implement a solution with a linear runtime complexity and use only constant extra space.   Example 1:  Input: nums = [2,2,1] Output: 1  Example 2:  Input: nums = [4,1,2,1,2] Output: 4  Example 3:  Input: nums = [1] Output: 1    Constraints:  1 <= nums.length <= 3 * 104 -3 * 104 <= nums[i] <= 3 * 104 Each element in the array appears twice except for one element which appears only once.  

	# Explanation
	Here's the solution to find the single number in an array where every other number appears twice, optimized for linear runtime and constant space:

*   **Leverage XOR:** The XOR (exclusive OR) operation has the property that `a ^ a = 0` and `a ^ 0 = a`. Therefore, XORing all elements in the array will cancel out the pairs, leaving only the single number.
*   **Iterate and XOR:** Iterate through the array, applying the XOR operation cumulatively.
*   **Return the Result:** The final result of the XOR operation will be the single number.

*   **Runtime Complexity:** O(n), **Storage Complexity:** O(1)

	
	# Code
	```python
	def singleNumber(nums):
    """
    Finds the single number in an array where every other number appears twice.

    Args:
        nums: A list of integers.

    Returns:
        The single number that appears only once.
    """
    result = 0
    for num in nums:
        result ^= num
    return result
	```