Introduction

In this blog post, we will explore how to solve the LeetCode problem "1695" 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

You are given an array of positive integers nums and want to erase a subarray containing unique elements. The score you get by erasing the subarray is equal to the sum of its elements. Return the maximum score you can get by erasing exactly one subarray. An array b is called to be a subarray of a if it forms a contiguous subsequence of a, that is, if it is equal to a[l],a[l+1],...,a[r] for some (l,r). Example 1: Input: nums = [4,2,4,5,6] Output: 17 Explanation: The optimal subarray here is [2,4,5,6]. Example 2: Input: nums = [5,2,1,2,5,2,1,2,5] Output: 8 Explanation: The optimal subarray here is [5,2,1] or [1,2,5]. Constraints: 1 <= nums.length <= 105 1 <= nums[i] <= 104

Explanation

Here's the solution:

• Sliding Window: Use a sliding window to maintain a subarray of unique elements. Expand the window to the right, and if a duplicate is encountered, shrink the window from the left until the duplicate is removed.
• Sum Calculation: Maintain a running sum of the elements within the current window. Update the maximum score encountered so far.

• Hash Set for Uniqueness: Employ a hash set (or dictionary) to efficiently track the elements present in the current window, enabling fast duplicate detection and removal.

• Runtime Complexity: O(n), where n is the length of the input array.

• Storage Complexity: O(k), where k is the number of unique elements in the input array (at most 10^4 based on constraints).

Code

    def maximumUniqueSubarray(nums):
    """
    Calculates the maximum score of a subarray with unique elements.

    Args:
        nums: A list of positive integers.

    Returns:
        The maximum score.
    """

    seen = set()
    max_score = 0
    current_score = 0
    left = 0

    for right in range(len(nums)):
        while nums[right] in seen:
            seen.remove(nums[left])
            current_score -= nums[left]
            left += 1

        seen.add(nums[right])
        current_score += nums[right]
        max_score = max(max_score, current_score)

    return max_score