How should I practice In-Memory Filesystem Commands?

Start by reading the full statement, solve the visible examples, then compare the pattern against related Perplexity AI phone screen problems in FastPrep.

Is In-Memory Filesystem Commands associated with Perplexity AI?

FastPrep tags this as a Perplexity AI phone screen coding practice problem when the problem catalog has that company and stage context.

Problem · Design

In-Memory Filesystem Commands

Learn this problem

● Medium

Perplexity AIFULLTIMEPHONE SCREEN

Problem statement

Process a sequence of commands against an in-memory filesystem. The root directory / exists initially, and the current directory starts at the root. Paths beginning with / are absolute; every other path is resolved beneath the current directory.

["MKDIR", path] creates one empty directory when its parent directory exists and the path is unused.
["TOUCH", path] creates one file under an existing directory when the path is unused.
["LS", path] lists the immediate child names of an existing directory in lexicographic order, joined by commas.
["RM", path] removes an existing file.
["RMDIR", path] removes an existing empty directory unless it is the root, the current directory, or an ancestor of the current directory.
["CD", path] changes the current directory when the path identifies an existing directory.

Return one string per command. A successful mutation or directory change returns "true", while a rejected one returns "false". A failed LS returns "NULL"; listing an empty directory returns the empty string.

Function

runFileSystem(operations: String[][]) → String[]

Examples

Example 1

operations = [["MKDIR","/docs"],["TOUCH","/docs/readme"],["CD","/docs"],["MKDIR","drafts"],["TOUCH","drafts/plan"],["LS","/docs"],["CD","drafts"],["RM","plan"],["RMDIR","/docs"],["CD","/"],["RMDIR","/docs/drafts"],["LS","/docs"]]return = ["true","true","true","true","true","drafts,readme","true","true","false","true","true","readme"]

Relative paths use the current directory. An ancestor of the current directory cannot be removed, but the empty drafts directory can be removed after returning to the root.

Example 2

operations = [["MKDIR","/b"],["MKDIR","/a"],["TOUCH","/a/z"],["TOUCH","/a/m"],["LS","/"],["LS","/a"],["LS","/a/z"],["CD","/missing"],["RM","/a"],["RMDIR","/"]]return = ["true","true","true","true","a,b","m,z","NULL","false","false","false"]

Listings are lexicographic, LS on a file returns NULL, and commands reject targets of the wrong type.

Constraints

1 <= operations.length <= 100000
Every operation has exactly one documented shape.
A path is either / or a canonical absolute or relative path. Non-root paths contain one or more lowercase ASCII letter, digit, or underscore components separated by single slashes, with no leading slash for relative paths and no trailing slash.
Paths do not contain . or .. components.
Each path has at most 100 components and at most 1000 characters.
The total number of characters across all operations is at most 1000000.
The total number of child names emitted by all successful LS commands is at most 200000.