#Arrays

Given an array of integers representing the heights of barriers, compute how much water can be trapped after raining. You need to provide an optimized approach that performs better than O(n^2).

Solve the Array Intersection problem. Please discuss your approach and consider edge cases in your solution.

What are the advantages of using hashmaps over arrays?

Discuss the differences between arrays and hashmaps in JavaScript.

Given two sorted arrays, merge them into the first array without using extra space. Handle cases where one of the arrays may include missing elements represented by -1.