How do you find the smallest range that includes at least one number from each of k sorted lists?
PICTURE THIS: GIT FLOW
Simple meaning
Push the current head of each list into a min-heap and track the max among those k heads
WHY — Sliding Window instead of guessing?
Why interviewers care about Sliding Window:
question about Sliding Window.
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:
- 1Push the current head
of each list into a min-heap and track the max among those k heads
- 2pop the min, replace
it with the next from that list, and update max.
- 3Heap operations give O(n
log k) time and O(k) space for n total elements.
- 4A two-pointer merge on
flattened pairs also works after tagging list ids.
- 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
Push the current head of each list into a min-heap and track the max among those k heads pop the min, replace it with the next from that list, and update max.