algorithm-in-python/sort/quickSort.py
2018-10-02 21:24:06 +08:00

108 lines
3.3 KiB
Python

''' mbinary
#########################################################################
# File : quickSort.py
# Author: mbinary
# Mail: zhuheqin1@gmail.com
# Blog: https://mbinary.coding.me
# Github: https://github.com/mbinary
# Created Time: 2018-07-06 10:31
# Description:
#########################################################################
'''
def quickSort(lst):
'''A optimized version of Hoare partition'''
def partition(a,b):
pivot = lst[a]
while a!=b:
while a<b and lst[b]>pivot: b-=1
if a<b:
lst[a] = lst[b]
a+=1
while a<b and lst[a]<pivot: a+=1
if a<b:
lst[b] = lst[a]
b-=1
lst[a] = pivot
return a
def _sort(a,b):
if a>=b:return
mid = (a+b)//2
# 三数取中值置于第一个作为 pivot
if (lst[a]<lst[mid]) ^ (lst[b]<lst[mid]): lst[a],lst[mid] = lst[mid],lst[a] # lst[mid] 为中值
if (lst[a]<lst[b]) ^ (lst[b]>lst[mid]): lst[a],lst[b] = lst[b],lst[a] # lst[b] 为中值
i = partition(a,b)
_sort(a,i-1)
_sort(i+1,b)
_sort(0,len(lst)-1)
return lst
def quickSort2(lst):
'''A version of partition from <Introduction of Algorithm>, a little bit slow'''
def partition(a,b):
pivot = lst[b]
j = a-1
for i in range(a,b):
if lst[i]<=pivot:
j+=1
if i!=j: lst[i], lst[j] = lst[j], lst[i]
lst[j+1],lst[b] = lst[b],lst[j+1]
return j+1
def _sort(a,b):
if a>=b:return
mid = (a+b)//2
# 三数取中值置于第一个作为 pivot
if (lst[a]<lst[mid]) ^ (lst[b]<lst[mid]): lst[b],lst[mid] = lst[mid],lst[b] # lst[mid] 为中值
if (lst[a]>lst[b]) ^ (lst[a]>lst[mid]): lst[a],lst[b] = lst[b],lst[a] # lst[b] 为中值
i = partition(a,b)
_sort(a,i-1)
_sort(i+1,b)
_sort(0,len(lst)-1)
return lst
def quickSort3(lst):
'''A rear recursive optimization version'''
def partition(a,b):
pivot = lst[b]
j = a-1
for i in range(a,b):
if lst[i]<=pivot:
j+=1
if i!=j: lst[i], lst[j] = lst[j], lst[i]
lst[j+1],lst[b] = lst[b],lst[j+1]
return j+1
def _sort(a,b):
while a<b:
mid = (a+b)//2
# 三数取中值置于第一个作为 pivot
if (lst[a]<lst[mid]) ^ (lst[b]<lst[mid]): lst[b],lst[mid] = lst[mid],lst[b] # lst[mid] 为中值
if (lst[a]>lst[b]) ^ (lst[a]>lst[mid]): lst[a],lst[b] = lst[b],lst[a] # lst[b] 为中值
i = partition(a,b)
_sort(a,i-1)
a = i+1
_sort(0,len(lst)-1)
return lst
from time import time
def timer(func,lst,n=100):
t = time()
for i in range(n):func(lst)
t = time()-t
print('{}: {}s'.format(func.__name__,t))
return t
if __name__ == '__main__':
from random import randint
print('5000 items, repeat 100 times for each')
lst = [randint(0,100) for i in range(5000)]
timer(quickSort,lst.copy())
timer(quickSort2,lst.copy())
timer(quickSort3,lst.copy())
lst = [randint(0,100) for i in range(15)]
print(lst)
print(quickSort(lst.copy()))
print(quickSort2(lst.copy()))
print(quickSort3(lst.copy()))