How do you solve House Robber II when houses are in a circle?
PICTURE THIS: HOW TO EXPLAIN IT
Simple meaning
You cannot rob both first and last, so take the max of linear-rob on [0..n-2] and on [1..n-1], with a one-house base case.
WHY — DP instead of guessing?
Why interviewers care about DP:
question about DP.
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:
- 1You cannot rob both
first and last, so take the max of linear-rob on [0..n-2] and on [1..n-1], with a one-house base case.
- 2Each linear pass is
O(n) time and O(1) space.
- 3A single DP over
a circle without splitting double-counts the wrap edge.
- 4Give an example
One tiny concrete case you can say aloud.
- 5Common mistake
What juniors usually get wrong.
- 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
You cannot rob both first and last, so take the max of linear-rob on [0..n-2] and on [1..n-1], with a one-house base case. Each linear pass is O(n) time and O(1) space.