How do you implement a circular queue with a fixed array?
PICTURE THIS: ARRAY IN MEMORY
Index starts at 0. Scan once for max — O(n).
Simple meaning
Keep a buffer, head index, count (or head and tail), and capacity.
WHY — Queue instead of guessing?
Why interviewers care about Queue:
question about Queue.
trade-offs, and what you would actually do on a DSA project - not buzzwords.
Name the idea, why it exists, then one short example.
End with when you use it and one common pitfall.
STEPS — What happens step by step?
Before you speak the answer, walk the interviewer through these steps:
- 1Keep a buffer, head
index, count (or head and tail), and capacity.
- 2Why it exists
Enqueue writes at (head+count)%cap
- 3How it works
dequeue reads head then advances.
- 4All operations are O(1)
time and O(k) space.
- 5Using count avoids the
full/empty aliasing that a tail pointer alone can cause.
- 6Close
When you pick this over the alternative.
EXAMPLE — See it in action
Here's a short line you can speak, broken into clear beats:
Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.
Key takeaway
Keep a buffer, head index, count (or head and tail), and capacity. Enqueue writes at (head+count)%cap