python 的 heapq.heapify() 在接近堆的列表上是否更快？

Question

Like the title says, I would like to know if python's heapq.heapify() will work faster on a list that is close to a heap or does it do the entire operation element by element on every list?

I'm debating on how often to use heapify().

Answer 1

The obvious answer is yes. If you supply a sorted array to heapify it won't have to perform any swaps at all. If you supply a reverse-sorted array it will have to perform the maximum number of swaps.

That said, there is no benefit to pre-sorting the array before passing it to heapify because the total time (ie analyzing and arranging the array, plus heapify time) will exceed the maximum time required for heapify to do its work on even the worst-case arrangement.