Calculate trapped rain water: No basin

What this Python exercise asks you to practise

This scenario tests calculate trapped rain water. It belongs to the Algorithm Foundations: Arrays, Searching, Sorting, and Hashing roadmap and uses the leetcode pattern · two pointers · hard pattern.

Complexity, linear and binary search, sorted() trade-offs, prefix ideas, two pointers, sliding windows, and hash-map patterns.

Pattern relevance

This exercise strengthens leetcode pattern · two pointers · hard. Be ready to explain the input, the rule, the boundary cases, and why the chosen approach is appropriate.