algorithm: heap sort in python 算法导论 堆排序

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