Question

使用python heap implementation的一个简单示例是

>>> from heapq import heappush, heappop
>>> heap = []
>>> data = [1, 3, 5, 7, 9, 2, 4, 6, 8, 0]
>>> for item in data:
        heappush(heap, item)

在一个更复杂的场景中，我有一组像

这样的元组

tuples = [(5,"foo",True),(2,"bar", False),(8,"foobar",True)]

并希望将每个元组的第一个条目用作堆密钥，即元组应根据堆中的元组中的数字进行排序。

我该怎么做？

Answer 1

您可以直接使用元组。 Python documentation explicitly makes note等用法：

堆元素可以是元组。这对于在跟踪的主记录旁分配比较值（例如任务优先级）非常有用：
>>> h = []
>>> heappush(h, (5, 'write code'))
>>> heappush(h, (7, 'release product'))
>>> heappush(h, (1, 'write spec'))
>>> heappush(h, (3, 'create tests'))
>>> heappop(h)
(1, 'write spec')

只需将元组推入堆中，并在需要时将其弹出：

>>> from heapq import heappush, heappop
>>> 
>>> heap = []
>>> tuples = [(5,"foo",True),(2,"bar", False),(8,"foobar",True)] 
>>> 
>>> for tup in tuples:
...     heappush(heap, tup)
... 
>>> heappop(heap)
(2, 'bar', False)

因为the implementation for heap使用元组的默认排序

while pos > startpos:
    ...
    if newitem < parent:
        ...
    ...
...

并且Python按元素排序元组，确保首先对元组进行排序的对象。

为元组数组定义堆键

1 个答案: