Design In-Memory File System

Start by clarifying the exact contract for In-Memory File System: input representation, mutation rules, duplicate behavior, and what should happen on invalid or empty input. The core idea is tree modeling and path-operation semantics. Work a tiny example aloud and name the invariant after each step, because that is the proof that the approach stays correct as the input grows.

A dependable implementation plan is to represent directories with child maps; normalize path components; traverse from root; create directories as specified; distinguish append from overwrite. Files cannot safely act as intermediate directories. Keep the code aligned with that invariant instead of adding special cases that silently change the contract. Test the smallest input, a normal case, duplicates or ties where relevant, an adversarial boundary, and a case that exercises the failure path. The expected complexity is O(k) traversal for k path components. Explain both time and auxiliary memory, including recursion or helper structures; do not hide sorting, copying, or repeated scans. If the title omits critical constraints, say what you need to know before committing to a more specialized solution.