How do you find the minimum window in s that covers all characters of t, including duplicates?
PICTURE THIS: HOW TO EXPLAIN IT
Simple meaning
Expand right while missing needed counts, then shrink left as long as the window stays valid, tracking the smallest span.
WHY — Strings instead of guessing?
Why interviewers care about Strings:
question about Strings.
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:
- 1Expand right while missing
needed counts, then shrink left as long as the window stays valid, tracking the smallest span.
- 2With a need map
and a missing counter each pointer moves O(n): O(|s| + |t|) time and O(alphabet) space.
- 3Nested search of every
start is O(n^2) and too slow.
- 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
Expand right while missing needed counts, then shrink left as long as the window stays valid, tracking the smallest span. With a need map and a missing counter each pointer moves O(n): O(|s| + |t|) time and O(alphabet) space.