python实现堆排序

#!/usr/bin/env python
# -*- coding: utf-8 -*-

def heap_sort(arr):
l = len(arr)
for i in xrange(l/2, -1, -1):
form_heap(arr, i, l-1)
for i in xrange(l-1, 0, -1):
arr[i],arr[0] = arr[0],arr[i]
form_heap(arr, 0, i-1)
return

def form_heap(arr, start, end):
while(start < end):
tmp = start * 2
if tmp > end:
break
if tmp +1 <= end and  arr[tmp + 1] > arr[tmp]:
tmp = tmp + 1
if arr[tmp] > arr[start]:
arr[tmp],arr[start] = arr[start], arr[tmp]
start = tmp

heap_sort(arr)
#form_heap(arr, 3,len(arr) -1)
print arr