# -*- coding:utf-8 -*- class Array(object): def __init__(self, size=32): self._size = size self._items = [None] * size def __getitem__(self, index): return self._items[index] def __setitem__(self, index, value): self._items[index] = value def __len__(self): return self._size def clear(self, value=None): for i in range(len(self._items)): self._items[i] = value def __iter__(self): for item in self._items: yield item class MaxHeap(object): def __init__(self, maxsize=None): self.maxsize = maxsize self._elements = Array(maxsize) self._count = 0 def __len__(self): return self._count def add(self, value): if self._count >= self.maxsize: raise Exception('full') self._elements[self._count] = value self._count += 1 self._siftup(self._count-1) def _siftup(self, ndx): if ndx > 0: parent = int((ndx-1)/2) if self._elements[ndx] > self._elements[parent]: self._elements[ndx], self._elements[parent] = self._elements[parent], self._elements[ndx] self._siftup(parent) def extract(self): if self._count <= 0: raise Exception('empty') value = self._elements[0] self._count -= 1 self._elements[0] = self._elements[self._count] self._siftdown(0) return value def _siftdown(self, ndx): left = 2 * ndx + 1 right = 2 * ndx + 2 # determine which node contains the larger value largest = ndx if (left < self._count and # 有左孩子 self._elements[left] >= self._elements[largest] and self._elements[left] >= self._elements[right]): # 原书这个地方没写实际上找的未必是largest largest = left elif right < self._count and self._elements[right] >= self._elements[largest]: largest = right if largest != ndx: self._elements[ndx], self._elements[largest] = self._elements[largest], self._elements[ndx] self._siftdown(largest) def test_maxheap(): import random n = 5 h = MaxHeap(n) for i in range(n): h.add(i) for i in reversed(range(n)): assert i == h.extract() def heapsort_reverse(array): length = len(array) maxheap = MaxHeap(length) for i in array: maxheap.add(i) res = [] for i in range(length): res.append(maxheap.extract()) return res def test_heapsort_reverse(): import random l = list(range(10)) random.shuffle(l) assert heapsort_reverse(l) == sorted(l, reverse=True) def heapsort_use_heapq(iterable): from heapq import heappush, heappop items = [] for value in iterable: heappush(items, value) return [heappop(items) for i in range(len(items))] def test_heapsort_use_heapq(): import random l = list(range(10)) random.shuffle(l) assert heapsort_use_heapq(l) == sorted(l) 