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Grokking the Coding Interview Patterns in Go

Solution: Count Pairs in Two Arrays

Explore how to count pairs (i, j) where the sum from one array exceeds the other using sorting and binary search. Understand how to reduce a complex condition to a difference array, and apply sorting and binary search techniques to efficiently count valid pairs with improved time complexity from O(n²) to O(n log n). This lesson helps you build confidence in applying algorithmic strategies like binary search and sorting to solve array comparison problems efficiently.

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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 = ...