The Trapped Pool

A hard Python interview practice problem on DataDriven. Write and execute real python code with instant grading.

Domain

Python

Difficulty

hard

Seniority

L5

Problem

A terrain survey hands you an elevation profile as a list of non-negative `heights`, each bar one unit wide. After a storm, water pools in the dips between taller bars, while anything past the outer edges drains away. Return the total units of water the profile holds once the level settles.

Summary

What collects in the valleys after the rain?

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