Introduction

In this blog post, we will explore how to solve the LeetCode problem "2574" 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 of size n. Define two arrays leftSum and rightSum where: leftSum[i] is the sum of elements to the left of the index i in the array nums. If there is no such element, leftSum[i] = 0. rightSum[i] is the sum of elements to the right of the index i in the array nums. If there is no such element, rightSum[i] = 0. Return an integer array answer of size n where answer[i] = |leftSum[i] - rightSum[i]|. Example 1: Input: nums = [10,4,8,3] Output: [15,1,11,22] Explanation: The array leftSum is [0,10,14,22] and the array rightSum is [15,11,3,0]. The array answer is [|0 - 15|,|10 - 11|,|14 - 3|,|22 - 0|] = [15,1,11,22]. Example 2: Input: nums = [1] Output: [0] Explanation: The array leftSum is [0] and the array rightSum is [0]. The array answer is [|0 - 0|] = [0]. Constraints: 1 <= nums.length <= 1000 1 <= nums[i] <= 105

Explanation

• Prefix and Suffix Sums: Calculate the total sum of the array. Then, iterate through the array, maintaining a running left_sum. The right_sum can be efficiently computed by subtracting left_sum and the current element from the total sum.
  • Avoid Extra Arrays: The leftSum and rightSum arrays are not explicitly created, saving space. The calculations are done inline to compute the absolute difference efficiently.
  • In-place Calculation: The absolute differences are calculated and stored directly in the result array.

• Runtime Complexity: O(n), Storage Complexity: O(1) (excluding the output array).

Code

    def leftRightDifference(nums):
    n = len(nums)
    answer = [0] * n
    total_sum = sum(nums)
    left_sum = 0
    for i in range(n):
        right_sum = total_sum - left_sum - nums[i]
        answer[i] = abs(left_sum - right_sum)
        left_sum += nums[i]
    return answer