The In-Memory File System

The file system comes up more than any other coding problem at Perplexity. It's mostly a phone screen question, with a few sightings at the onsite. You build it in parts inside one CoderPad session, and part one tends to look like LeetCode 588.

The later parts are where time runs out, since each one adds a rule that changes how a path is handled.

Neither of those needs new tree code if part one was built around one shared path lookup, a single helper that walks a path from the root and returns the node. If you copy the path loop into each method instead, every new rule turns into several edits against the clock. So write that helper first, and have every command go through it. Below are the three parts as separate problems, worked in order, so you can see how the same core carries each new rule.

PerplexityPremium lesson · Coding round

The 3 Perplexity problems are below.

1. 1A Premium questionCoding · Medium · Signature problem
2. 2A Premium questionCoding · Hard · Frequently asked
3. 3A Premium questionCoding · Medium · Frequently asked

Each with hints, the follow-up and a tested solution.

Get the Perplexity questions

$49 a year · all 100 companies · cancel anytime

From 20,000+ candidate reports, forum threads behind logins and write-ups in Chinese.

Read a free Perplexity lesson firstAlready a member? Sign in