Citadel is a fintech company that many science and engineering students dream of, especially its Quant and Software Engineer positions, which have high salaries, hardcore technology, and difficult questions. This article organizes Citadel OA real experience + three mock questions review, suitable for students who are ready to submit the collection.
Introduction to the Interview Process
Citadel The OA is generally conducted by the CodeSignal or HackerRank platforms, and is overall on the LeetCode Hard difficulty side.
Question Coverage:
- Algorithms + Data Structures (HF: heap, greedy, double pointer, interval handling)
- Mathematical modeling (portfolio / simulated trading behavior)
- String and Matrix Handling (looks simple, but stuck at the border)
OA Question Review
Q1. Task Scheduling with Limited Threads
Title in brief:
You are given a set of tasks, each with startTime respond in singing endTime, indicating that it can only be executed in this time interval. You have k Threads can perform tasks in parallel. Ask how many tasks can be completed at most?
Input Example:
tasks = [[1, 4], [2, 6], [4, 7], [5, 8]]
k = 2
Output:
3Q2. Profit Maximization with Transaction Cooldown
Title in brief:
Given an array of stock prices pricesIf you buy, you must wait at least one day before you can sell, and you must wait one day after you sell before you can buy again (cooldown 1 day). Maximize profit.
Input Example:
prices = [1, 2, 3, 0, 2]
Output:
3Problem Solving Ideas:
Three states are designed: Hold / Cool / Empty, which are realized by the state transfer equation DP.
Q3. String Mutation Validation
Title in brief:
Given two strings s1 respond in singing s2, determine whether the s1 change into s2: Each operation can replace a segment of consecutive characters with another character (segment length is unlimited) for an unlimited number of operations.
Input Example:
s1 = "aabbcc"
s2 = "xyzxyz"
Output:
TrueProblem Solving Ideas:
Divide the string into chunks, keep the character mapping consistent between corresponding chunks, and check the mapping relationship of each segment.
High Frequency Stops & Suggestions for Passing the Levels
- There is a lot of time pressure:Proficiency in heap, state machine DP, and interval processing is recommended.
- Limited debugging window:The platform does not have a complete log, and the logic must be written correctly at once.
- Code Style:Clear variable names + appropriate comments.
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