Citadel Software Engineer Interview Questions
Practice the exact questions companies are asking right now.
Compute max team size with a core interval
You are given n employees’ working-time intervals, where employee i works during the inclusive interval [startTime[i], endTime[i]]. You want to form a...
Build models for housing and wind power prediction
Two-Part Machine Learning Take-Home Part 1 — Binary Classification: "Can Buy" vs "Cannot Buy" Given applicant and market data, design a binary classif...
Describe current work and relocation willingness
Behavioral Screen: Responsibilities, Project Deep Dive, and Relocation You are interviewing for a Software Engineer role in a behavioral/leadership HR...
Explain career motivations and choices
Behavioral Fit Prompts for a Software Engineer (Technical Screen) Context: You are interviewing for a Software Engineer role in the finance industry d...
Solve four algorithmic problems
Answer the following independent algorithmic questions: 1) Count extendable prefixes for '10' subsequences: Given a binary string s and an integer k, ...
Explain role, motivations, values, and relocation expectations
HR Screen: Role, Motivation, Values, and NYC Relocation/Compensation Context: You are interviewing for a Software Engineer role. The recruiter wants a...
Find earliest common meeting slot
Given K participants' calendars, each a list of busy intervals [start, end) within a working window [workStart, workEnd], and a meeting duration d min...
Discuss queues, NoSQL, and concurrency
System Design Concepts: Messaging, Storage Choices, and Concurrency Context: You are designing distributed services that communicate via events and mu...
Design a low-latency trading system
System Design: Low-Latency Electronic Trading Platform (Equities) You are designing a single-region electronic trading platform (exchange/ATS-like) th...
Explain background, priorities, and relocation terms
HR Screen: Self-Introduction, Team Context, Transition, Values, Relocation, Compensation Context You are preparing for an HR screen for a Software Eng...
Minimize image processing cost with discount
Question You have n images. For the i-th image, processing costs filterCost[i] per day and must run from startDay[i] to endDay[i] inclusive. Each day ...
Minimize changes for k-periodic palindrome
Question Given a string currentPassword (length N) and an integer k (1 ≤ k < N, N ≤ 2·10^5, lowercase letters, N divisible by k), find the minimum num...
Optimize password transform and discount scheduling
Part 1 — Transform to palindromic k-periodic string: Input: a lowercase string currentPassword and integer k. Constraints: 1 <= k < len(currentPasswor...
Explain JS types, Promises, Maps, WebSockets
JavaScript Types, Promises, Collections, and WebSocket Ordering You are interviewing for a software engineering role. Answer the following about JavaS...
Explain hash maps and solve array intersection
1) Explain the internal implementation of a hash map: underlying array/bucket layout, hash function choice, collision resolution strategies (separate ...
Solve two DS&A optimization problems
Problem 1 — Maximize alternating-sum over four array partitions: Given an integer array arr[1..n] (1-based). Choose indices a, b, c with 1 ≤ a ≤ b ≤ c...