Is Valid K-Unique Subarrays II easy or hard?

This problem is rated Hard. The brute force is easy, but the optimal sliding window requires the right insight, making it challenging under interview conditions. It is a common follow-up to easier substring counting problems.

Valid K-Unique Subarrays II Python solution?

The Python solution uses a helper function atMost(k) with a dictionary. Iterate right, add to freq, shrink left while len(freq) > k, then add right - left + 1. Finally return atMost(k) - atMost(k-1).

How to solve Valid K-Unique Subarrays II in O(n)?

Use two pointers to maintain a window with at most K distinct elements. Track frequencies in a hash map. For each right pointer, adjust the left pointer until the map size is ≤ K, then add right - left + 1 to the count. Compute atMost(K) and atMost(K-1) and subtract.

What is the best approach for Valid K-Unique Subarrays II?

The sliding window approach that counts subarrays with at most K distinct elements and subtracts atMost(K-1) is the best. It runs in O(n) time and uses O(n) space, making it both efficient and interview-friendly.

Is Valid K-Unique Subarrays II asked at Google/Amazon/Meta?

Yes, this problem is classic and frequently appears in interviews at top companies like Google, Amazon, and Meta. It tests your ability to apply sliding window and hash map patterns under time pressure.

What data structure is used in Valid K-Unique Subarrays II?

A hash map (dictionary) is used to store frequencies of elements inside the current window. It allows O(1) insertion, deletion, and lookups, which is essential for the O(n) sliding window solution.

What is the time complexity of Valid K-Unique Subarrays II?

The optimal solution using sliding window achieves O(n) time complexity, where n is the array length. The space complexity is O(n) in the worst case due to the frequency map.

4042. Valid K-Unique Subarrays II - Practice Online

4042. Valid K-Unique Subarrays II

Hard50.0% AcceptancePremium

PremiumFree on FleetCode

Problem description not available.

Loading editor...

No test cases available.