kFrequent

Given a (possibly empty) Python list of integers and a non-negative integer k, find the k most frequent elements in the Python list using heap.

Note:

• k may not always be valid, i.e., the number of distinct elements in the Python list may be less than k.

• If two elements have the same frequency and they can not both be included, then only the smaller element is included.

• Return the elements in a Python list. The order of the elements does not matter.

• The runtime is O(min(k, n)logn). When not using heap, the runtime is O(nlogn).

• Example: Given nums = [5,3,9,10,10,6,6,5] and k = 2, return [6,5] (or [5,6]).