How do you solve climbing stairs when you may take 1 or 2 steps?
PICTURE THIS: HOW TO EXPLAIN IT
Simple meaning
The number of ways to reach n is ways(n-1) plus ways(n-2), the same recurrence as Fibonacci.
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:
- 1The number of ways
to reach n is ways(n-1) plus ways(n-2), the same recurrence as Fibonacci.
- 2Bottom-up O(n) time and
O(1) space by keeping two previous counts.
- 3Recursion without memo is
exponential and will time out in interviews.
- 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
The number of ways to reach n is ways(n-1) plus ways(n-2), the same recurrence as Fibonacci. Bottom-up O(n) time and O(1) space by keeping two previous counts.