Cracking the Citadel Software Engineer Interview: Insights on OLS and Coding Challenges

Software Engineering
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citadel | Software Engineer | Interview Experience

Interview Date: Not specified
Result: Not specified
Difficulty: Not specified

Interview Process

The interview consisted of four rounds, each lasting approximately 45 minutes.

  • First Round: Focused on coding questions without any extensive review of the resume. The candidate was asked to perform an Ordinary Least Squares (OLS) regression using a given nxp matrix, selecting columns as target and feature variables, and to analyze the time complexity. The candidate initially used a straightforward method before discussing a more efficient approach.

  • Second Round: This round involved a deeper exploration of the candidate’s resume. The coding question required the candidate to determine the number of islands in a given mxn 2D grid representing land and water. Additionally, the candidate was presented with a problem involving stock return prediction based on a random walk model, requiring them to devise a prediction strategy and compute the correlation between predicted and actual returns.

  • Third Round: The interviewer briefly reviewed the candidate’s resume and posed a coding challenge related to caching stock prices. The candidate was tasked with implementing a long-term cache solution and optimizing data retrieval for large datasets, discussing potential methods using JSON, pickle, and file handling.

  • Fourth Round: This round included a simple review of the resume followed by a coding question involving probability. The candidate was asked to calculate the probability that a tetrahedron formed by four randomly selected points on a sphere contains the origin, which the candidate approached through a Monte Carlo simulation.

Technical Questions

  1. Coding: Given an nxp matrix A, perform OLS regression.
  2. Coding: Given an mxn 2D grid, return the number of islands. (Leetcode 200)
  3. Problem: Predict the stock return based on a random walk model.
  4. Coding: Implement a cache for stock prices and optimize data retrieval.
  5. Coding: Calculate the probability that a tetrahedron formed by four points on a sphere contains the origin using Monte Carlo simulation.

Tips & Insights

  • Focus on understanding the underlying concepts of algorithms and data structures.
  • Be prepared to discuss your resume in detail and relate your past experiences to the interview questions.
  • Practice coding problems from platforms like Leetcode to familiarize yourself with common interview questions.
  • When faced with complex problems, consider breaking them down into simpler components or using simulations to find solutions.