Coding problem: Moving Median. Given a list of integers `values` and a window size `k`, return the median of every window of `k` consecutive values, from left to right. There are `len(values) - k + 1` windows; return an empty list when `k` is larger than the list.

What the interviewer is looking for

• What a strong solution looks like: two heaps — a max-heap for the lower half and a min-heap for the upper half — with lazy deletion of values leaving the window (a hash map of pending removals) and rebalancing; or a sorted container with binary-search insert and delete. Heaps give O(n log k). A sorted list with bisect insert/remove is O(n·k) in the worst case but fast in practice; re-sorting every window is O(n·k log k). Accept the simpler versions if they can explain the cost.
• Think aloud. Interviewers are judging how you reason, not only the final code.
• Be ready for: A moving average is O(1) per step — why is the median harder? Approximate percentiles over an unbounded stream (t-digest, HDR histograms). How would you report p95 latency per minute across a fleet?

A structure to follow: Clarify, plan, code, test, analyse

1. Step 1

   Clarify

   Restate the problem, ask about empty input, duplicates and size limits, and agree on one example.

2. Step 2

   Plan

   Say the simple approach first and its cost, then the better one. Explain why before you type.

3. Step 3

   Code

   Write small named steps and talk through each. A clear solution beats a clever one.

4. Step 4

   Test

   Walk your own example through the code, then an edge case. Fix what you find calmly.

5. Step 5

   Analyse

   State time and space cost in plain words and say what you would change for much larger input.

This is guidance on shape, not a script. Use your own real experience and facts; never invent details to fill a gap. See the STAR guide and answer frameworks.

Common slips

• Starting to code before agreeing what the answer must be.
• Going silent when stuck instead of saying what you are trying.
• Never running your own example through the code.

How to practise it

Solve it once in the editor without hints, then explain your solution aloud in under two minutes.

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