# Solving Leetcode Interviews in Seconds with AI: Decode XORed Array


	# Introduction
	In this blog post, we will explore how to solve the LeetCode problem "1720" 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
	> There is a hidden integer array arr that consists of n non-negative integers. It was encoded into another integer array encoded of length n - 1, such that encoded[i] = arr[i] XOR arr[i + 1]. For example, if arr = [1,0,2,1], then encoded = [1,2,3]. You are given the encoded array. You are also given an integer first, that is the first element of arr, i.e. arr[0]. Return the original array arr. It can be proved that the answer exists and is unique.   Example 1:  Input: encoded = [1,2,3], first = 1 Output: [1,0,2,1] Explanation: If arr = [1,0,2,1], then first = 1 and encoded = [1 XOR 0, 0 XOR 2, 2 XOR 1] = [1,2,3]  Example 2:  Input: encoded = [6,2,7,3], first = 4 Output: [4,2,0,7,4]    Constraints:  2 <= n <= 104 encoded.length == n - 1 0 <= encoded[i] <= 105 0 <= first <= 105  

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

*   **Approach:**
    *   Initialize the original array `arr` with the given `first` element.
    *   Iterate through the `encoded` array. For each element `encoded[i]`, calculate `arr[i+1]` using the XOR property: `arr[i+1] = arr[i] ^ encoded[i]`. Append the calculated value to `arr`.
    *   Return the constructed `arr`.

*   **Complexity:**
    *   Runtime Complexity: O(n), where n is the length of the `encoded` array.
    *   Storage Complexity: O(n) to store the resulting `arr` array.

	
	# Code
	```python
	def decode(encoded, first):
    """
    Decodes the original array from the encoded array and the first element.

    Args:
        encoded: The encoded array.
        first: The first element of the original array.

    Returns:
        The original array.
    """
    arr = [first]
    for i in range(len(encoded)):
        arr.append(arr[i] ^ encoded[i])
    return arr
	```