python计算最小优先级队列代码分享

代码如下:
# -*- coding: utf-8 -*-

class Heap(object):

    @classmethod
    def parent(cls, i):
        """父结点下标"""
        return int((i - 1) >> 1);

    @classmethod
    def left(cls, i):
        """左儿子下标"""
        return (i << 1) + 1;

    @classmethod
    def right(cls, i):
        """右儿子下标"""
        return (i << 1) + 2;

class MinPriorityQueue(list, Heap):

    @classmethod
    def min_heapify(cls, A, i, heap_size):
        """最小堆化A[i]为根的子树"""
        l, r = cls.left(i), cls.right(i)
        if l < heap_size and A[l] < A[i]:
            least = l
        else:
            least = i
        if r < heap_size and A[r] < A[least]:
            least = r
        if least != i:
            A[i], A[least] = A[least], A[i]
            cls.min_heapify(A, least, heap_size)

    def minimum(self):
        """返回最小元素，伪码如下：
        HEAP-MINIMUM(A)
        1  return A[1]

        T(n) = O(1)
        """
        return self[0]

    def extract_min(self):
        """去除并返回最小元素，伪码如下：
        HEAP-EXTRACT-MIN(A)
        1  if heap-size[A] < 1
        2    then error "heap underflow"
        3  min ← A[1]
        4  A[1] ← A[heap-size[A]] // 尾元素放到第一位
        5  heap-size[A] ← heap-size[A] - 1 // 减小heap-size[A]
        6  MIN-HEAPIFY(A, 1) // 保持最小堆性质
        7  return min

        T(n) = θ(lgn)