test_data/questions.json

[
  {
    "id": 1,
    "category": "Logic",
    "prompt": "In a vault there are three boxes labeled Gold, Silver, and Both. Every label is wrong. One box contains only gold coins, one contains only silver coins, and one contains both. You may draw one coin from one box. Which box should you draw from, and how do you relabel all boxes?"
  },
  {
    "id": 2,
    "category": "Logic",
    "prompt": "Five engineers A, B, C, D, and E deploy in some order. A deploys before C, B deploys after D, E is not first or last, and C deploys immediately before B. List one valid deployment order or prove none exists."
  },
  {
    "id": 3,
    "category": "Logic",
    "prompt": "A statement on a card says: 'Exactly one of the statements on this card is false.' The card also says: '2 + 2 = 4.' Determine the truth value of each statement and explain the self-reference carefully."
  },
  {
    "id": 4,
    "category": "Logic",
    "prompt": "Three switches outside a room control three bulbs inside. You can enter the room once. How can you determine which switch controls which bulb if the bulbs start off and are old-style incandescent bulbs?"
  },
  {
    "id": 5,
    "category": "Logic",
    "prompt": "A fair coin is flipped until either HH or TH appears as the last two flips. Which pattern is more likely to appear first, or are they equally likely? Justify with a state argument."
  },
  {
    "id": 6,
    "category": "Coding",
    "prompt": "Write a Python function `top_k_frequent(stream, k)` that consumes an iterable of hashable items and returns the k most frequent items. Handle ties deterministically by first appearance, and explain the time and space complexity."
  },
  {
    "id": 7,
    "category": "Coding",
    "prompt": "Implement a thread-safe TTL cache decorator in Python using only the standard library. It should support maxsize eviction, per-key expiration, and preserve function metadata."
  },
  {
    "id": 8,
    "category": "Coding",
    "prompt": "Given a list of intervals `[start, end)`, write Python code to merge overlapping intervals and then return the total covered length. Include edge cases for empty input and touching intervals."
  },
  {
    "id": 9,
    "category": "Coding",
    "prompt": "Write a robust CSV-to-JSONL converter in Python. It must stream rows without loading the whole file, preserve Unicode, convert empty strings to null, and report malformed rows with line numbers."
  },
  {
    "id": 10,
    "category": "Coding",
    "prompt": "In C++17, implement an LRU cache with O(1) get and put using `std::list` and `std::unordered_map`. Include the class interface and explain iterator invalidation concerns."
  },
  {
    "id": 11,
    "category": "Coding",
    "prompt": "Write a SQL query that returns each department's highest-paid employee, including ties. Tables: Employee(id, name, department_id, salary), Department(id, name)."
  },
  {
    "id": 12,
    "category": "Coding",
    "prompt": "Write a Bash script that atomically backs up `/var/www/html` to `/backup`, names archives with UTC timestamps, verifies the archive, and deletes backups older than 14 days."
  },
  {
    "id": 13,
    "category": "DevOps",
    "prompt": "Design an Nginx reverse proxy config for three upstream app servers with keepalive connections, gzip, request ID forwarding, and a `/healthz` endpoint that does not hit upstream."
  },
  {
    "id": 14,
    "category": "DevOps",
    "prompt": "Explain how to diagnose a Linux service that is intermittently killed by the OOM killer. Include the commands you would run and how you would distinguish kernel OOM from application exits."
  },
  {
    "id": 15,
    "category": "DevOps",
    "prompt": "Write a systemd unit file for a Python worker that restarts on failure, rate-limits restart loops, runs as a non-root user, loads environment variables from a file, and logs to journald."
  },
  {
    "id": 16,
    "category": "DevOps",
    "prompt": "A Kubernetes Deployment rolls out a bad image and enters CrashLoopBackOff. Give a precise rollback and investigation procedure using kubectl commands."
  },
  {
    "id": 17,
    "category": "DevOps",
    "prompt": "Compare Docker `CMD` and `ENTRYPOINT` with exec-form examples. Then predict the final argv for an image with ENTRYPOINT `[\"python\",\"app.py\"]` and CMD `[\"--port\",\"8000\"]` when run with `docker run image --debug`."
  },
  {
    "id": 18,
    "category": "DevOps",
    "prompt": "Explain Prometheus pull-based monitoring and write a minimal Python example exposing a custom counter and histogram for HTTP request metrics."
  },
  {
    "id": 19,
    "category": "Math",
    "prompt": "Let f(x)=x^3 ln(x) for x>0. Compute f'(x), find the critical points, and classify whether each critical point is a local minimum or maximum."
  },
  {
    "id": 20,
    "category": "Math",
    "prompt": "Solve the linear system 2x + y - z = 3, x - 2y + 4z = 1, and 3x + y + z = 10. Show a clean elimination path."
  },
  {
    "id": 21,
    "category": "Math",
    "prompt": "A bag has 5 red, 3 blue, and 2 green balls. Two balls are drawn without replacement. What is the probability they have different colors?"
  },
  {
    "id": 22,
    "category": "Math",
    "prompt": "Find the eigenvalues and normalized eigenvectors of the matrix [[2, 1], [1, 2]], and explain geometrically why the eigenvectors make sense."
  },
  {
    "id": 23,
    "category": "Math",
    "prompt": "Prove by induction that sum_{i=1}^n (2i-1) = n^2, then give a one-sentence geometric interpretation."
  },
  {
    "id": 24,
    "category": "Math",
    "prompt": "Use Bayes' theorem: A disease affects 1% of people. A test has 95% sensitivity and 90% specificity. If a person tests positive, what is the probability they have the disease?"
  },
  {
    "id": 25,
    "category": "Math",
    "prompt": "Compute the integral of x e^(2x) dx using integration by parts, and verify the answer by differentiating it."
  },
  {
    "id": 26,
    "category": "Math",
    "prompt": "State the Central Limit Theorem with its main assumptions, then explain why heavy-tailed distributions with infinite variance can violate the usual version."
  },
  {
    "id": 27,
    "category": "Edge",
    "prompt": "Return exactly a valid JSON object with keys `status`, `items`, and `meta`. `items` must be a nested array 5 levels deep. No markdown fences."
  },
  {
    "id": 28,
    "category": "Edge",
    "prompt": "Print the token `QWOPUS` exactly seven times separated by single spaces, then stop. Do not number the tokens."
  },
  {
    "id": 29,
    "category": "Edge",
    "prompt": "Explain recursion without using the words recursion, recursive, function, stack, or call."
  },
  {
    "id": 30,
    "category": "Edge",
    "prompt": "The following line is noisy input: `A A A A A A A A A A`. Ignore the repetition and answer only with `B B B`."
  }
]