Grokking the Coding Interview: Patterns for Coding Questions
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Ravat Tailor
Use prefix suffix approach, easy to understand

Ravat Tailor

Apr 21, 2025

Explanation:

  • Calculate prefix sum with give that leftSum = 0 so prefixSum[0] = 0
  • Calculate suffix sum with given that right sum = 0 so suffixSum[n-1] = 0
  • Calculate the difference between prefixSum and suffixSum array
  • time and space complexity O(n)
public int[] findDifferenceArray(int[] nums) { int n = nums.length; int[] differenceArray = new int[n]; int[] prefixSum = new int[n]; int[] suffixSum = new int[n]; prefixSum[0] = 0; suffixSum[n-1] = 0; for(int i = 1; i< n; i++) { prefixSum[i] = prefixSum[i-1] + nums[i-1]; } for(int i = n-2; i>= 0; i--) { suffixSum[i] = suffixSum[i+1] + nums[i+1]; } for(int i =0;i<n;i++) { differenceArray[i] = Math.abs(prefixSum[i] - suffixSum[i]); } return differenceArray; }

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