Grokking Data Structures & Algorithms for Coding Interviews
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Problem 3: Left and Right Sum Differences (easy)
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Problem Statement

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Problem Statement

Given an input array of integers nums, find an integer array, let's call it differenceArray, of the same length as an input integer array.

Each element of differenceArray, i.e., differenceArray[i], should be calculated as follows: take the sum of all elements to the left of index i in array nums (let's call it leftSum<sup>i</sup>), and subtract it from the sum of all elements to the right of index i in array nums (let's call it rightSum<sup>i</sup>), taking the absolute value of the result:

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differenceArray[i] = | leftSum<sup>i</sup> - rightSum<sup>i</sup> |

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If there are no elements to the left or right of i, the corresponding sum should be taken as 0.

Examples

Example 1:

  • Input: nums = [2, 5, 1, 6, 1]
  • Expected Output: [13, 6, 0, 7, 14]
  • Explanation:
    • For i=0: |(0) - (5+1+6+1)| = |0 - 13| = 13
    • For i=1: |(2) - (1+6+1)| = |2 - 8| = 6
    • For i=2: |(2+5) - (6+1)| = |7 - 7| = 0
    • For i=3: |(2+5+1) - (1)| = |8 - 1| = 7
    • For i=4: |(2+5+1+6) - (0)| = |14 - 0| = 14

Example 2:

  • Input: nums = [3, 3, 3]
  • Expected Output: [6, 0, 6]
  • Explanation:
    • For i=0: |(0) - (3+3)| = 6
    • For i=1: |(3) - (3)| = 0
    • For i=2: |(3+3) - (0)| = 6

Example 3:

  • Input: nums = [1, 2, 3, 4, 5]
  • Expected Output: [14, 11, 6, 1, 10]
  • Explanation:
    • Calculations for each index i will follow the above-mentioned logic.

Constraints:

  • 1 <= nums.length <= 1000
  • 1 <= nums[i] <= 10<sup>5</sup>

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Python3
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Table of Contents

Problem Statement

Examples

Try it yourself