Compiler, Math and Logic Puzzle Interview Questions

All 59 questions

1. What is the difference between a compiler and an interpreter?

   Asked in 3 of 374 interviews · last asked Oct 18 · Concept · Junior

   Show answer

   A compiler translates code into another form, such as machine code or bytecode, for execution. An interpreter runs code by processing its instructions at runtime. Both can work together: CPython compiles Python source to bytecode, then runs that bytecode in its interpreter.

   • Compilation does not always produce machine code.
   • Interpreters do not necessarily execute source code one line at a time.
   • Some systems also compile code during execution, called just-in-time compilation.

   What the interviewer checks: The interviewer checks whether you understand translation versus execution and how both can work together.

   Other ways it was asked

   • “What is the difference between a compiler and an interpreter when executing Python?”
   • “What is a compiler and an interpreter?”

2. What is an annotated parse tree?

   Asked in 2 of 374 interviews · last asked Mar 27 · Concept · Junior

   Other ways it was asked

   • “What is the difference between a parse tree and an annotated parse tree, and what is a parse tree?”
   • “What is a parse tree?”

3. What are the phases of a compiler?

   Asked in 2 of 374 interviews · last asked Mar 27 · Concept · Junior

4. Do Gauss's variation equations always allow larger time steps, or can they become numerically unstable?

   Asked once · last asked Apr 15 · Concept · Senior

   Other ways it was asked

   • “What other conditions can make Gauss's variation equations numerically unstable?”

5. If q(x) = k(x-a)(x-b)(x-c) and p(x) = q(x) + 7, what is the general form of p(x)?

   Asked once · last asked Jul 21 · Concept · Junior

   Other ways it was asked

   • “If q(x) = p(x) - 7 and q(x) = k(x-a)(x-b)(x-c), what condition must hold at x = d for q(d) to equal 3?”
   • “For q(x) = k(x-a)(x-b)(x-c), what must k(d-a)(d-b)(d-c) equal for q(d) to equal 3?”
   • “If q(x) = k(x-a)(x-b)(x-c) and p(x) = q(x) + 7, does the factor k change when forming p(x)?”

6. What are LLVM and MLIR, and how are they used in compiler development?

   Asked once · last asked Aug 12 · Concept · Senior

7. You have 16 memory sticks in a server and one is faulty. How would you locate it with the fewest iterations?

   Asked once · last asked Feb 3 · Scenario · Mid-level

8. What is the difference between top-down and bottom-up parsing?

   Asked once · last asked Mar 27 · Concept · Junior

   Other ways it was asked

   • “When would you use top-down versus bottom-up parsing in a real-time application?”

9. In what cases would the condition that the time derivative of the relative distance is zero fail to identify the time of closest approach?

   Asked once · last asked Apr 15 · Scenario · Senior

10. When would you choose analytical rather than numerical propagation, or vice versa, and what are the forces and trade-offs involved?

    Asked once · last asked Apr 15 · Concept · Senior

11. Why use an adaptive step size rather than a fixed one, and in what situations would you use each?

    Asked once · last asked Apr 15 · Concept · Mid-level

12. How would adaptive versus fixed step sizes affect orbit propagation in near-Earth orbit and GEO?

    Asked once · last asked Apr 15 · Scenario · Senior

13. What methods do you commonly use in numerical analysis?

    Asked once · last asked May 19 · Concept · Mid-level

14. How do you use Lean, Rocq, or Isabelle in research involving formal proofs?

    Asked once · last asked Jul 16 · Tooling · Mid-level

15. How would you translate reinforcement learning work into a formal proof workflow using Lean or Isabelle?

    Asked once · last asked Jul 16 · Tooling · Senior

16. How would you parse colon-delimited input into an object and determine which value belongs to each field?

    Asked once · last asked Jul 16 · Write code · Mid-level

17. How would you split colon-delimited records and convert them into a list of objects?

    Asked once · last asked Jul 16 · Write code · Mid-level

18. What should a tokenizer output, and how can that output affect the parser and later execution?

    Asked once · last asked Jul 16 · Concept · Mid-level

19. Let p be a cubic polynomial with value 7 at three distinct integers and value 10 at another integer. What happens to the three points where p(x) = 7 when you shift p down by 7?

    Asked once · last asked Jul 21 · Concept · Mid-level

20. If q(x) = k(x-a)(x-b)(x-c), what is its degree, and how is its leading coefficient related to k?

    Asked once · last asked Jul 21 · Concept · Junior

21. What makes an optimization pass correct, and how would you test and validate it?

    Asked once · last asked Aug 12 · Concept · Senior

22. You have nine identical-looking tennis balls, one of which is heavier than the others. What is the minimum number of weighings on a balance scale needed to guarantee finding the heavier ball?

    Asked once · last asked Aug 27

    Other ways it was asked

    • “Let's say I give you nine tennis balls. They all look the same, but one is heavier. With a balanced scale, how many minimum tries do you need to find the heavy ball?”
    • “If there are n balls and one is heavier, what is the minimum number of weighings needed to identify it with a balanced scale?”

23. There are two pirates. Pirate one has seven troops, and pirate two has eight troops. There are three ships worth five, three, and two points, respectively. Pirate one may distribute his seven troops among the ships however he likes, including assigning zero troops to a ship. Pirate two distributes his eight troops uniformly at random among the three ships. For each ship, the pirate who assigns more troops wins its points; if they assign the same number, the points are split equally. Assuming pirate one chooses his deployment optimally, what is his expected final score?

    Asked once · last asked Aug 29

24. Why would you choose interpolation as an approach to a problem?

    Asked once · last asked Aug 31 · Concept · Mid-level

25. How would you represent a large exponent b as an array of digits and process it?

    Asked once · last asked Sep 7 · Write code · Mid-level

26. You have 10 bags of coins: nine contain 10-gram coins, and one contains 9-gram coins. How can you identify the odd bag using a digital scale and only one weighing?

    Asked once · last asked Sep 11

27. An infinitely large hotel has a guest in every room. Can it still accommodate a new guest?

    Asked once · last asked Sep 11

28. In a hotel with infinitely many rooms, all occupied, where could the guest in room 300 move as part of a plan to accommodate one new guest?

    Asked once · last asked Sep 11

    Other ways it was asked

    • “In an infinitely full hotel, where should the guest in room 300 move to make room for a new guest?”

29. How can you measure exactly 4 liters of water using an unmarked 3-liter jug and an unmarked 5-liter jug?

    Asked once · last asked Sep 11

30. How can you measure exactly 45 minutes using two ropes that each take 60 minutes to burn but burn unevenly?

    Asked once · last asked Sep 11

31. What is the smaller angle between the hour and minute hands of an analog clock at 3:15?

    Asked once · last asked Sep 11

32. What does a dot product such as 5 or −1 indicate about the directions of two vectors, and how can it help assess their alignment?

    Asked once · last asked Dec 18 · Concept · Junior

33. How would you parse a variable number of JSON objects from one string, and is a regular expression the right approach?

    Asked once · last asked Oct 1 · Scenario · Mid-level

34. How would you extract three JSON objects from one string?

    Asked once · last asked Oct 1 · Scenario · Mid-level

35. Five houses are arranged in a row: white, gray, brown, pink, and orange. The white house is somewhere to the left of the brown house, orange is immediately to the right of pink, brown is not at either end, and gray is between white and brown. How are they arranged?

    Asked once · last asked Oct 13

36. In the range 1 to 100, how many odd prime numbers are present, and how do you find them?

    Asked once · last asked Oct 14 · Write code · Junior

    Other ways it was asked

    • “In the range 1 to 100, how many odd numbers are present, and how do you determine that count?”

37. How can a compiler efficiently resolve function lookups across an inheritance hierarchy?

    Asked once · last asked Oct 16 · Scenario · Senior

38. What does “RK” stand for in RK4 and RK45?

    Asked once · last asked Apr 15 · Concept · Junior

    Other ways it was asked

    • “What do the “4” in RK4 and the “4/5” in RK45 stand for?”

39. What is a finite-state machine?

    Asked once · last asked Feb 9 · Concept · Junior

    Other ways it was asked

    • “What are finite-state machines used for?”

40. What are some examples of simple finite-state machines?

    Asked once · last asked Feb 9 · Concept · Junior

41. What is a basic block?

    Asked once · last asked Mar 27 · Concept · Junior

42. What is a flow graph?

    Asked once · last asked Mar 27 · Concept · Junior

43. What is the purpose of the Lex tool?

    Asked once · last asked Mar 27 · Concept · Junior

44. Which tool is used to generate a parser?

    Asked once · last asked Mar 27 · Concept · Junior

45. What is passed to the parser?

    Asked once · last asked Mar 27 · Concept · Junior

46. What are the different methods of parsing?

    Asked once · last asked Mar 27 · Concept · Junior

47. Can you explain the spline method?

    Asked once · last asked May 19 · Concept · Junior

48. What is bicubic interpolation?

    Asked once · last asked May 19 · Concept · Junior

49. Write pseudocode to solve an equation provided as a string.

    Asked once · last asked Nov 17 · Write code · Junior

50. If q(x) = p(x) - 7, how can you express p(x) in terms of q(x)?

    Asked once · last asked Jul 21 · Concept · Junior

51. How does adding 7 to q(x) affect the roots of the resulting polynomial p(x) = q(x) + 7?

    Asked once · last asked Jul 21 · Concept · Mid-level

52. What are permutations and combinations? Please provide a simple example for each.

    Asked once · last asked Jul 27 · Concept · Junior

53. What is the Roman numeral for 3, and how would you approach converting integers to Roman numerals?

    Asked once · last asked Aug 31 · Write code · Junior

54. What is 90 in Roman numerals?

    Asked once · last asked Aug 31 · Write code · Junior

55. What is a compiler?

    Asked once · last asked Sep 3 · Concept · Junior

56. Why is the Fibonacci series important?

    Asked once · last asked Sep 8 · Concept · Junior

57. What are arithmetic, geometric, and harmonic progressions?

    Asked once · last asked Sep 8 · Concept · Junior

58. What applications do dot products have, and what kinds of problems are they used to solve?

    Asked once · last asked Dec 18 · Concept · Junior

59. How do you calculate the dot product of two vectors when their coordinates are known?

    Asked once · last asked Dec 18 · Concept · Junior

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How this list is made

Every question here was asked by a real interviewer in a real job interview that a candidate ran MeetAssist in. After the call, the interviewer's questions are pulled from the transcript. Practice sessions, tests, exams and anything that was not a job interview are dropped.

Questions are rewritten so they make sense on their own: names of people, employers and clients are removed, and speech-to-text mistakes are fixed. Small talk, logistics and questions about one candidate's own résumé are left out. Rephrasings of the same question are merged, and the count is the number of different interviews it came up in.

The interviews come from candidates who use MeetAssist, so they lean towards software, data and AI roles: the shares describe these interviews, not every Data Structures and Algorithms interview. Answers to the most asked questions are written and checked by an editor; a "common mistake" is shown only when reviews of real answers in these interviews show it, with the count.

374 interviews, 269 candidates, Sep 2025 to Oct 2026. Updated every month with new interviews.