Introduction

In this blog post, we will explore how to solve the LeetCode problem "2615" 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. There exists an array arr of length nums.length, where arr[i] is the sum of |i - j| over all j such that nums[j] == nums[i] and j != i. If there is no such j, set arr[i] to be 0. Return the array arr. Example 1: Input: nums = [1,3,1,1,2] Output: [5,0,3,4,0] Explanation: When i = 0, nums[0] == nums[2] and nums[0] == nums[3]. Therefore, arr[0] = |0 - 2| + |0 - 3| = 5. When i = 1, arr[1] = 0 because there is no other index with value 3. When i = 2, nums[2] == nums[0] and nums[2] == nums[3]. Therefore, arr[2] = |2 - 0| + |2 - 3| = 3. When i = 3, nums[3] == nums[0] and nums[3] == nums[2]. Therefore, arr[3] = |3 - 0| + |3 - 2| = 4. When i = 4, arr[4] = 0 because there is no other index with value 2. Example 2: Input: nums = [0,5,3] Output: [0,0,0] Explanation: Since each element in nums is distinct, arr[i] = 0 for all i. Constraints: 1 <= nums.length <= 105 0 <= nums[i] <= 109 Note: This question is the same as 2121: Intervals Between Identical Elements.

Explanation

Here's the breakdown of the problem and the solution:

• High-Level Approach:

  • Use a dictionary to store the indices of each number in nums.
  • Iterate through nums. For each element, retrieve the list of indices where the same number appears. Calculate the sum of absolute differences between the current index and all other indices in the list.
  • Store the calculated sum in the result array arr.

• Complexity:

  • Runtime: O(n), where n is the length of nums.
  • Storage: O(n), where n is the length of nums. This is because, in the worst case, all the elements in nums can be the same, and the dictionary might store all the indices.

Code

    def interval_between_identical_elements(nums):
    """
    Calculates the sum of absolute differences between indices of identical elements.

    Args:
        nums: A 0-indexed integer array.

    Returns:
        An array arr of the same length as nums, where arr[i] is the sum of |i - j|
        over all j such that nums[j] == nums[i] and j != i.
    """
    index_map = {}
    for i, num in enumerate(nums):
        if num not in index_map:
            index_map[num] = []
        index_map[num].append(i)

    arr = [0] * len(nums)
    for i in range(len(nums)):
        if nums[i] in index_map:
            indices = index_map[nums[i]]
            for j in indices:
                if i != j:
                    arr[i] += abs(i - j)

    return arr