python - Python中的最小/最大堆实现

这是我在python中实现的MinHeap和MaxHeap。这使用比较器来反转MaxHeap中的存储顺序

import heapq


class MinHeap:
    def __init__(self):
        self.heap = []

    def push(self, item):
        heapq.heappush(self.heap, item)

    def pop(self):
        return heapq.heappop(self.heap)

    def peek(self):
        return self.heap[0]

    def __getitem__(self, item):
        return self.heap[item]

    def __len__(self):
        return len(self.heap)


class MaxHeap(MinHeap):
    def push(self, item):
        heapq.heappush(self.heap, Comparator(item))

    def pop(self):
        return heapq.heappop(self.heap)

    def peek(self):
        return self.heap[0]

    def __getitem__(self, i):
        return self.heap[i].val


class Comparator:
    def __init__(self, val):
        self.val = val

    def __lt__(self, other):
        return self.val > other

    def __eq__(self, other):
        return self.val == other




if __name__ == '__main__':
    max_heap = MaxHeap()
    max_heap.push(12)
    max_heap.push(3)
    max_heap.push(17)
    print(max_heap.pop())

MinHeap似乎工作正常，但是MaxHeap抛出以下错误。

<__main__.Comparator object at 0x10a5c1080>

我似乎不太了解我在这里做错了什么。有人可以帮我弄这个吗。

最佳答案

我已将__repr__和__gt__方法添加到您的Comparator类中，因此代码现在可以运行，并且Comparator实例在打印时显示其val。

重要的是要使这些比较方法在两个Comparator实例之间正确进行比较。

您会注意到，我从MaxHeap中删除​​了大多数方法。不需要它们是因为从MinHeap继承的方法可以正常工作。您不妨将其还原到MaxHeap

def __getitem__(self, i):
    return self.heap[i].val

取决于您打算如何使用MaxHeap。

import heapq

class MinHeap:
    def __init__(self):
        self.heap = []

    def push(self, item):
        heapq.heappush(self.heap, item)

    def pop(self):
        return heapq.heappop(self.heap)

    def peek(self):
        return self.heap[0]

    def __getitem__(self, item):
        return self.heap[item]

    def __len__(self):
        return len(self.heap)

class MaxHeap(MinHeap):
    def push(self, item):
        heapq.heappush(self.heap, Comparator(item))

class Comparator:
    def __init__(self, val):
        self.val = val

    def __lt__(self, other):
        return self.val > other.val

    def __eq__(self, other):
        return self.val == other.val

    def __repr__(self):
        return repr(self.val)

if __name__ == '__main__':
    max_heap = MaxHeap()
    max_heap.push(12)
    max_heap.push(3)
    max_heap.push(17)

    while True:
        try:
            print(max_heap.pop())
        except IndexError:
            # The heap's empty, bail out
            break

输出

17
12
3

为Comparator提供全套丰富的比较方法可能是一个好主意。他们不需要使上面的代码正常工作，但是可以使Comparator实例更加灵活。因此，如果您需要它们，这里是：

def __lt__(self, other):
    return self.val > other.val

def __le__(self, other):
    return self.val >= other.val

def __gt__(self, other):
    return self.val < other.val

def __ge__(self, other):
    return self.val <= other.val

def __eq__(self, other):
    return self.val == other.val

def __ne__(self, other):
    return self.val != other.val