Introduction

In this blog post, we will explore how to solve the LeetCode problem "2760" 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 a 0-indexed integer array nums and an integer threshold. Find the length of the longest subarray of nums starting at index l and ending at index r (0 <= l <= r < nums.length) that satisfies the following conditions: nums[l] % 2 == 0 For all indices i in the range [l, r - 1], nums[i] % 2 != nums[i + 1] % 2 For all indices i in the range [l, r], nums[i] <= threshold Return an integer denoting the length of the longest such subarray. Note: A subarray is a contiguous non-empty sequence of elements within an array. Example 1: Input: nums = [3,2,5,4], threshold = 5 Output: 3 Explanation: In this example, we can select the subarray that starts at l = 1 and ends at r = 3 => [2,5,4]. This subarray satisfies the conditions. Hence, the answer is the length of the subarray, 3. We can show that 3 is the maximum possible achievable length. Example 2: Input: nums = [1,2], threshold = 2 Output: 1 Explanation: In this example, we can select the subarray that starts at l = 1 and ends at r = 1 => [2]. It satisfies all the conditions and we can show that 1 is the maximum possible achievable length. Example 3: Input: nums = [2,3,4,5], threshold = 4 Output: 3 Explanation: In this example, we can select the subarray that starts at l = 0 and ends at r = 2 => [2,3,4]. It satisfies all the conditions. Hence, the answer is the length of the subarray, 3. We can show that 3 is the maximum possible achievable length. Constraints: 1 <= nums.length <= 100 1 <= nums[i] <= 100 1 <= threshold <= 100

Explanation

• Iterate and Check: The solution iterates through the nums array, using each index as a potential starting point (l) for a valid subarray. For each l, it extends the subarray to the right (r) as long as the conditions are met.
  • Condition Verification: Inside the inner loop, it checks if each element nums[i] within the subarray is less than or equal to the threshold and if the parity (even or odd) alternates between consecutive elements. The starting element must be even.
  • Maximum Length: The solution keeps track of the maximum length of a valid subarray found so far and updates it whenever a longer valid subarray is encountered.

• Runtime Complexity: O(n^2), Storage Complexity: O(1)

Code

    def longest_alternating_subarray(nums, threshold):
    """
    Finds the length of the longest subarray of nums starting at index l and ending at index r
    that satisfies the given conditions.

    Args:
        nums: A 0-indexed integer array.
        threshold: An integer.

    Returns:
        An integer denoting the length of the longest such subarray.
    """
    max_length = 0
    n = len(nums)

    for l in range(n):
        if nums[l] % 2 == 0 and nums[l] <= threshold:
            current_length = 1
            for r in range(l + 1, n):
                if nums[r] <= threshold and nums[r] % 2 != nums[r - 1] % 2:
                    current_length += 1
                else:
                    break
            max_length = max(max_length, current_length)

    return max_length