Return the K Most Frequent Values with a Larger-Value Tie-Break

Question

The question asks the candidate to implement a function that returns the k most frequent elements from an array, ensuring that in the case of ties in frequency, the larger value is prioritized.

Codemia · Accepted Answer

To solve the problem of finding the k most frequent elements, I will first count the frequency of each element using a HashMap. Then, I will use a PriorityQueue to keep track of the top k elements based on their frequencies. If two elements have the same frequency, the larger element will be prioritized.

1. Create a HashMap to store the frequency of each element.
2. Iterate through the array and populate the HashMap.
3. Use a PriorityQueue (min-heap) to store the elements based on their frequencies. If the size of the heap exceeds k, remove the smallest element.
4. Extract the elements from the PriorityQueue into a list and return it.

Here is the Python code implementation:
```python
from collections import Counter
import heapq

def topKFrequent(nums, k):
    # Count the frequency of each element
    count = Counter(nums)
    # Use a min-heap to keep track of the top k elements
    heap = []
    for num, freq in count.items():
        heapq.heappush(heap, (freq, num))
        if len(heap) > k:
            heapq.heappop(heap)
    # Prepare the result list
    return [num for freq, num in heap]
```

The time complexity of this solution is O(N log k), where N is the number of elements in the input array. This is due to the insertion operation in the PriorityQueue which takes O(log k) time. The space complexity is O(N) for storing the frequency counts in the HashMap.

It is important to handle edge cases such as when k is greater than the number of unique elements in the array. In such cases, the function should return all unique elements sorted by their value.

Interviewers will look for clarity in your explanation, the ability to articulate your thought process, and how well you handle edge cases. They will also assess your coding skills, particularly your use of data structures and algorithm efficiency.

Return the K Most Frequent Values with a Larger-Value Tie-Break

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