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This is a Medium difficulty Coding & Algorithms question, commonly asked during Technical Screen rounds at DoorDash.

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This question is commonly asked for Software Engineer candidates at DoorDash during technical interviews.

Implement string-path file system operations

Company: DoorDash

Role: Software Engineer

Category: Coding & Algorithms

Difficulty: Medium

Interview Round: Technical Screen

##### Question LeetCode 1166. Design File System – extended to support Create(path, value), Get(path), Set(path, value) and Delete(path) with validation rules. https://leetcode.com/problems/design-file-system/description/

Quick Answer: This question evaluates competency in designing data structures for hierarchical string-path file systems, including string parsing, stateful API semantics, validation logic, and efficient lookup/update operations.

Implement a simple path-based file system that supports four operations over UNIX-like paths using strings. You are given a list of operations to process; return a result for each operation in order. Paths must start with '/', use '/' as a separator, have no empty segments, and may not end with '/' unless the path is exactly '/'. The root '/' exists by default and cannot be created, set, or deleted. The operations are: 1) Create(path, value): Create a node at 'path' with integer 'value' only if its parent exists and the path does not already exist. Returns True on success, False otherwise. 2) Get(path): Return the integer value stored at 'path', or -1 if the path does not exist or if 'path' is invalid or is '/'. 3) Set(path, value): Update the value at 'path' to 'value'. Returns True if the path exists and is valid (not '/'), otherwise False. 4) Delete(path): Remove the entire subtree rooted at 'path'. Returns True if the path exists and is not '/', otherwise False. Return for each operation: Create/Set/Delete -> boolean; Get -> integer. Input is a list of operations where each operation is one of: ['Create', path, value], ['Get', path], ['Set', path, value], ['Delete', path].

Constraints

1 <= len(ops) <= 50000
Sum of path lengths across all operations <= 2e6
Each value is a 32-bit signed integer
Paths use '/' as separator, start with '/', have no empty segments, and do not end with '/' unless the path is exactly '/'
Root '/' exists initially and cannot be created, set, or deleted
Create requires the immediate parent of the path to exist and the path to not already exist

Hints

Store the directory tree as nested hash maps (a trie-like structure).
Validate path format before performing any operation.
For Create, traverse to the parent; for Set/Get/Delete, traverse to the exact node.
Delete can be implemented by removing the child entry from its parent's map.

Quick Overview

This question evaluates competency in designing data structures for hierarchical string-path file systems, including string parsing, stateful API semantics, validation logic, and efficient lookup/update operations.