Calculate trapped water between elevation bars
Company: Tesla
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: Medium
Interview Round: Technical Screen
Given an array of non-negative integers representing the heights of unit-width vertical bars, compute the total water retained after rainfall. Start by presenting a brute-force approach and analyze its time and space complexity. Then optimize to a linear-time solution that uses constant extra space, explain the intuition, and implement the final method.
Quick Answer: This question evaluates array manipulation, algorithmic optimization, and complexity analysis, specifically the ability to reason about time and space trade-offs and design a linear-time, constant-space approach for computing trapped water.