Recursion Puzzles Quant Interview Guide
Recursion puzzles quant interview guide for state definitions, recurrence equations, base cases, examples, sanity checks, and mistakes.
Candidates solving repeated-state and self-similar puzzle prompts.
Recursion starts with state
A recursive puzzle needs a state variable that captures everything relevant about the remaining problem. Bad state definitions create messy or wrong recurrences.
Base cases stop the loop
Every recurrence needs clear base cases. For probability puzzles, boundaries often have values zero or one; for counting puzzles, small sizes anchor the sequence.
Concrete example
A hitting-probability problem can define p(i) as the chance of hitting the upper boundary from state i, then express p(i) using neighboring states.
Solve or reason from the recurrence
Sometimes the recurrence has a closed-form solution; sometimes the setup and small-case evaluation are enough. State what the interviewer is asking for.
Common mistakes
Candidates often write equations before defining state. The lazy reliable order is state, base cases, transition equation, then solve.
Practice the pattern
Use the LeetQuidity curriculum and calibration to turn this topic into a focused practice plan.