algorithm: heap sort in python 算法导论 堆排序

An Python implementation of heap-sort

based on the detailed algorithm description in Introduction to Algorithms Third Edition

import random



def max_heapify(arr, i, length):

    while True:

        l, r = i * 2 + 1, i * 2 + 2

        largest = l if l < length and arr[l] > arr[i] else i

        if r < length and arr[r] > arr[largest]:

            largest = r

        if largest != i:

            arr[i], arr[largest], i = arr[largest], arr[i], largest

        else:

            break



def build_heap(arr):

    for i in range(len(arr) / 2, -1, -1):

        max_heapify(l, i, len(arr))



def heap_sort(arr):

    build_heap(arr)

    length = len(arr)

    for i in range(1, length):

        arr[0], arr[-i] = arr[-i], arr[0]

        max_heapify(arr, 0, length - i)



if __name__ == '__main__':

    l = [random.randint(1, 113) for i in range(18)]

    print l

    heap_sort(l)

    print l