Introduction

In this blog post, we will explore how to solve the LeetCode problem "3471" 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 integer array nums and an integer k. An integer x is almost missing from nums if x appears in exactly one subarray of size k within nums. Return the largest almost missing integer from nums. If no such integer exists, return -1. A subarray is a contiguous sequence of elements within an array. Example 1: Input: nums = [3,9,2,1,7], k = 3 Output: 7 Explanation: 1 appears in 2 subarrays of size 3: [9, 2, 1] and [2, 1, 7]. 2 appears in 3 subarrays of size 3: [3, 9, 2], [9, 2, 1], [2, 1, 7]. 3 appears in 1 subarray of size 3: [3, 9, 2]. 7 appears in 1 subarray of size 3: [2, 1, 7]. 9 appears in 2 subarrays of size 3: [3, 9, 2], and [9, 2, 1]. We return 7 since it is the largest integer that appears in exactly one subarray of size k. Example 2: Input: nums = [3,9,7,2,1,7], k = 4 Output: 3 Explanation: 1 appears in 2 subarrays of size 4: [9, 7, 2, 1], [7, 2, 1, 7]. 2 appears in 3 subarrays of size 4: [3, 9, 7, 2], [9, 7, 2, 1], [7, 2, 1, 7]. 3 appears in 1 subarray of size 4: [3, 9, 7, 2]. 7 appears in 3 subarrays of size 4: [3, 9, 7, 2], [9, 7, 2, 1], [7, 2, 1, 7]. 9 appears in 2 subarrays of size 4: [3, 9, 7, 2], [9, 7, 2, 1]. We return 3 since it is the largest and only integer that appears in exactly one subarray of size k. Example 3: Input: nums = [0,0], k = 1 Output: -1 Explanation: There is no integer that appears in only one subarray of size 1. Constraints: 1 <= nums.length <= 50 0 <= nums[i] <= 50 1 <= k <= nums.length

Explanation

Here's the approach, complexity, and code:

• Count Occurrences: Iterate through all subarrays of size k and maintain a count of how many times each number appears in the subarrays.
• Filter and Find Max: Identify numbers that appear exactly once across all subarrays.

• Return Largest: Return the largest of these numbers, or -1 if none exist.

• Runtime Complexity: O(n*k), where n is the length of nums and k is the window size. Storage Complexity: O(n) in the worst case (if all elements of nums are distinct), to store the counts.

Code

    def largest_almost_missing(nums, k):
    """
    Finds the largest almost missing integer from nums.

    Args:
        nums: An integer array.
        k: An integer representing the subarray size.

    Returns:
        The largest almost missing integer from nums, or -1 if no such integer exists.
    """

    counts = {}
    n = len(nums)

    for i in range(n - k + 1):
        subarray = nums[i:i + k]
        for num in subarray:
            counts[num] = counts.get(num, 0) + 1

    almost_missing = []
    for num, count in counts.items():
        if count == 1:
            almost_missing.append(num)

    if not almost_missing:
        return -1
    else:
        return max(almost_missing)