How do you add two numbers stored as reversed linked lists?
PICTURE THIS: STACK VS QUEUE
Simple meaning
Walk both lists with a carry, creating a new node for (sum % 10) and carrying sum // 10.
WHY — Linked List instead of guessing?
Why interviewers care about Linked List:
question about Linked List.
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:
- 1Walk both lists with
a carry, creating a new node for (sum % 10) and carrying sum // 10.
- 2Handle unequal lengths and
a final leftover carry.
- 3Time is O(max(n,m)) and
space is O(max(n,m)) for the result.
- 4If digits were stored
forward, reverse first or use stacks.
- 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
Walk both lists with a carry, creating a new node for (sum % 10) and carrying sum // 10. Handle unequal lengths and a final leftover carry.