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Grokking the Coding Interview Patterns in JavaScript

Solution: Count Pairs in Two Arrays

Explore how to count valid index pairs in two arrays where the sum of elements in the first array is greater than that in the second. Understand how to optimize from a brute force O(n²) method to an efficient O(n log n) approach by using difference arrays, sorting, and binary search. Gain practical skills useful for coding interviews to solve problems involving sorting and search techniques.

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Statement

You are given two positive integer arrays, nums1 and nums2, both of length nn. Your task is to count and return the number of pairs of indexes (i,j)(i, j) where:

  • i<ji < j , and

  • nums1[i]+nums1[j]>nums2[i]+nums2[j]\text{nums1}[i] + \text{nums1}[j] > \text{nums2}[i] + \text{nums2}[j]

In simpler terms, the sum of two elements from nums1 must be greater than that of the corresponding elements from nums2.

Constraints:

  • n=n = ...