My first instinct was to sort the whole array and then do a sliding window pass, which works fine.
Clarify the problem and constraints, then propose sorting the array and using a sliding window to find the longest contiguous subarray with adjacent differences less than k. Since the subsequence must have distinct elements, handle duplicates by deduplication before applying the sliding window.
Pro tip: Always discuss edge cases and time/space complexity upfront; Amazon values candidates who consider scalability and real-world constraints like large inputs or duplicates.
Ask about input size, value ranges, and whether the subsequence must preserve original order. Confirm that 'subsequence' here means selecting elements and sorting them, so order doesn't matter.
Sort the array to bring close values together, then remove duplicates to ensure distinct elements. This simplifies the problem to finding the longest contiguous subarray where adjacent differences are less than k.
Use two pointers to maintain a window where the difference between the maximum and minimum elements is less than k. Since the array is sorted, this condition is equivalent to adjacent differences being less than k.
Expand the right pointer and shrink the left pointer when the condition fails, updating the maximum window length. Return the maximum length found.
State that sorting takes O(n log n) and the sliding window is O(n), so overall O(n log n) time and O(n) space for the sorted array. Walk through edge cases like k=1, empty array, or all duplicates.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.