How do you remove duplicates from a sorted array in place?
PICTURE THIS: ARRAY IN MEMORY
Index starts at 0. Scan once for max — O(n).
Simple meaning
A slow pointer marks the end of the unique prefix
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:
- 1A slow pointer marks
the end of the unique prefix
- 2a fast pointer copies
a value only when it differs from the last unique.
- 3One O(n) pass and
O(1) extra space, returning the new length.
- 4This only works because
equals are adjacent after sorting.
- 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
A slow pointer marks the end of the unique prefix a fast pointer copies a value only when it differs from the last unique.