How do you find all unique quadruplets that sum to a target?
PICTURE THIS: HASH MAP
Simple meaning
Sort, then two nested loops plus an inner two-pointer pair, skipping duplicates at every level.
WHY — Two Pointers instead of guessing?
Why interviewers care about Two Pointers:
question about Two Pointers.
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:
- 1Sort, then two nested
loops plus an inner two-pointer pair, skipping duplicates at every level.
- 2Time is O(n^3) after
O(n log n) sort, extra space O(1) besides output.
- 3Hashing inner two-sums is
similar time with more memory and messier dedup.
- 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
Sort, then two nested loops plus an inner two-pointer pair, skipping duplicates at every level. Time is O(n^3) after O(n log n) sort, extra space O(1) besides output.