Robinhood Software Engineer Onsite Coding Questions

I got the interview through a referral. Their questions were all the same ones I'd seen on forums and other sites, but I didn't pass because I felt I answered them quite well. The interviewers seemed

**Problem Statement** Exchanges only trade in whole shares, but the brokerage offers fractional shares to customers. The brokerage must manage an internal inventory to bridge this gap. The system must

Codewriting Overview: Our goal is to build a simplified version of a real Robinhood system that reads prices from a stream and aggregates those prices into historical datapoints aka candlestick charts. We\u2019re...

For onsite, I was asked an algorithms question similar to this: Users can refer each other to Robinhood. We want keep track of who is responsible for the most referrals and...

LeetCode #68: Text Justification. Difficulty: Hard. Topics: Array, String, Simulation. Asked at Robinhood in the last 6 months.

LeetCode #121: Best Time to Buy and Sell Stock. Difficulty: Easy. Topics: Array, Dynamic Programming. Asked at Robinhood in the last 6 months.

## Problem Given a list of words and a line width `W`, implement full text justification (like a word processor). Words on each line (except the last) must be spaced so the total line length equals exactly `W`. Spaces are distributed as evenly as possible; if uneven, extra spaces go to the leftmost gaps. The last line is left-justified with single spaces. ```python def full_justify(words: list[str], W: int) -> list[str]: pass ``` ## Example ``` Input: words = ["This", "is", "an", "example", "of", "text", "justification."] W = 16 Output: ["This is an", "example of text", "justification. "] ``` ## Follow-ups 1. How does your greedy line-breaking strategy perform vs. dynamic programming (Knuth-Plass)? 2. Extend to support RTL (right-to-left) text. 3. How would you handle words longer than `W`? 4. In a mobile layout context (variable-width fonts), how does the algorithm change?

## Problem: Build a Weekly Calendar (7x24) UI With Event Creation Implement a web **Weekly Calendar** component that displays a 7-day week. ### UI/Interaction Requirements 1. The calendar is a 2D g

## Referral Count (Descendant Count in a Referral Tree) You are given a referral network where each user (node) has **at most one referrer (parent)**. The relationships form a **tree or a forest**.

## Fractional Shares: Process Trades and Maintain Inventory Implement a program that processes a sequence of stock trade operations and maintains an up-to-date inventory (positions) per ticker. Trade

Given a list of non-empty strings `strings` and an integer `k` (number of lines/buckets). Process the strings in order and assign each string to one line. **Part 1 (any placement)** - Implement a met

You are given a sequence of calendar booking requests. Each request is an interval `[start, end)` (inclusive of `start`, exclusive of `end`) where time is represented by integers. Design a calendar s

You are given a sequence of requests, each represented as a string. The system supports (at least) the following request types: 1. `SIGNUP <user>`: register a new user. 2. `FRIEND_REQUEST <from> <to>

You are given a directed acyclic graph (DAG) describing service dependencies (edge `A -> B` means service A calls service B). Each service has a base request load (e.g., QPS). The effective load on a

## Problem: Implement Two Core Methods in an Android Stock Trading System Skeleton You are given an **Android/Java/Kotlin-style** stock trading system code skeleton (the interviewer provides several

## Problem: System Dependency Load Factor You are given a list of running programs `programs` and a 2D array `prerequisites` where `prerequisites[i] = [a, b]` means program **a depends on b** (a dire

## Problem statement Design a string validation system that handles security-related constraints. It should prevent maliciously constructed inputs from bypassing validation and maintain performance u

Given a directed acyclic graph with a specified entry point, each trigger of the entry point triggers its child nodes once and continues to trigger subsequent nodes. Calculate the trigger count for al

Implement the `findViewById(int id)` method in Android. Suppose you have a simple View hierarchy where each View has a unique ID. You need to find and return the corresponding View for a given ID. Des

Design a referral program leaderboard with relational support such that if A refers B, and B refers C, C's count adds to both A and B. Implement an efficient method to query the top 3 in the leaderboa