Peeking in a heap in python
Question:
What is the official way of peeking in a python heap as created by the heapq libs? Right now I have
def heappeak(heap):
smallest = heappop(heap)
heappush(heap, smallest)
return smallest
which is arguably, not very nice. Can I always assume that heap[0] is the top of the heap and use that? Or would that assume too much of the underlying implementation?
Answers:
Yes, you can make this assumption, because it is stated in the documentation:
Heaps are arrays for which heap[k] <= heap[2*k+1] and heap[k] <=
heap[2*k+2] for all k, counting
elements from zero. For the sake of
comparison, non-existing elements are
considered to be infinite. The
interesting property of a heap is that
heap[0] is always its smallest
element.
(And that’s probably the reason there is no peek function: there is no need for it.)
If you’re using Python 2.4 or newer, you can also use heapq.nsmallest().
What is the official way of peeking in a python heap as created by the heapq libs? Right now I have
def heappeak(heap):
smallest = heappop(heap)
heappush(heap, smallest)
return smallest
which is arguably, not very nice. Can I always assume that heap[0] is the top of the heap and use that? Or would that assume too much of the underlying implementation?
Yes, you can make this assumption, because it is stated in the documentation:
Heaps are arrays for which
heap[k] <= heap[2*k+1]andheap[k] <=for all k, counting
heap[2*k+2]
elements from zero. For the sake of
comparison, non-existing elements are
considered to be infinite. The
interesting property of a heap is that
heap[0]is always its smallest
element.
(And that’s probably the reason there is no peek function: there is no need for it.)
If you’re using Python 2.4 or newer, you can also use heapq.nsmallest().