What strategy removes duplicates from a sorted array efficiently?
This question focuses on modifying a sorted array in-place to remove duplicates. It tests the two-pointer technique and space optimization.
Why Interviewers Ask This
Interviewers use this to test the candidate's ability to optimize space usage by modifying arrays in-place. It checks if they understand the properties of sorted arrays and can leverage them for efficient algorithms. The question also evaluates attention to detail regarding return values and array lengths.
How to Answer This Question
Explain using a slow pointer to track the position of unique elements and a fast pointer to scan the array. When a new unique element is found, copy it to the slow pointer's position and increment the slow pointer. Return the new length. Emphasize O(n) time and O(1) space.
Key Points to Cover
- Sorted property utilization
- Slow and fast pointers
- In-place modification
- Correct length calculation
Sample Answer
Since the array is sorted, duplicates will be adjacent. I can use a two-pointer approach where the slow pointer marks the end of the unique subarray. The fast pointer scans through the array. Whenever the fast pointer fi…
Common Mistakes to Avoid
- Allocating a new array
- Incorrect pointer movement logic
- Returning wrong length value
Sound confident on this question in 5 minutes
Answer once and get a 30-second AI critique of your structure, content, and delivery. First attempt is free — no signup needed.