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, 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

    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