#! /usr/bin/env python3
# -*- coding=utf-8 -*-
'''
@Date: 2017-10-10
@Author: Henry
Python各种排序算法
'''
def bubble_sort(ls):
'''
冒泡排序
'''
if ls == None:
return []
else:
for j in range(len(ls)-1):
for k in range(len(ls)-j-1):
if ls[k] > ls[k+1]:
ls[k], ls[k+1] = ls[k+1], ls[k]
return ls
def fast_sort(ls):
'''
使用python的列表生成式的快速排序
'''
if len(ls) < 2:
return ls
else:
return fast_sort([x for x in ls[1:] if x <= ls[0]])
+ [ls[0]] + fast_sort([y for y in ls[1:] if y > ls[0]])
'''
标准快速排序
'''
def partition(L, first, last):
pivot = L[first]
leftmark = first + 1
rightmark = last
while True:
while L[leftmark] <= pivot:
if leftmark == rightmark:
break
leftmark += 1
while L[rightmark] > pivot:
rightmark -= 1
if leftmark < rightmark:
L[leftmark], L[rightmark] = L[rightmark], L[leftmark]
else:
break
L[first], L[rightmark] = L[rightmark], L[first]
return rightmark
def rand_partition(L, first, last):
'''
随机取得比较用的随机值
'''
import random
rand_num = random.randint(first, last)
L[first], L[rand_num] = L[rand_num], L[first]
pivot = L[first]
leftmark = first + 1
rightmark = last
while True:
while L[leftmark] <= pivot:
if leftmark == rightmark:
break
leftmark += 1
while L[rightmark] > pivot:
rightmark -= 1
if leftmark < rightmark:
L[leftmark], L[rightmark] = L[rightmark], L[leftmark]
else:
break
L[first], L[rightmark] = L[rightmark], L[first]
return rightmark
def std_quick_sort(L, first, last):
if first < last:
split = partition(L, first, last)
# split = rand_partition(L, first, last)
std_quick_sort(L, first, split-1)
std_quick_sort(L, split+1, last)
def stdQuickSort(L):
std_quick_sort(L, 0, len(L)-1)
# 标准快速排序结束
'''
选择排序，每次从剩余列表中选择最大值放在最后面，冒泡排序的升级，减少了swap操作
'''
def selection_sort(L):
for pos in range(len(L)-1, 0, -1):
positionMax = 0
for location in range(1, pos+1):
if L[location] > L[positionMax]:
positionMax = location
L[pos], L[positionMax] = L[positionMax], L[pos]
'''
插入排序
'''
def insertion_sort(alist):
for index in range(1, len(alist)):
currentvalue = alist[index]
position = index
while position > 0 and alist[position-1] > currentvalue:
alist[position] = alist[position-1]
position = position - 1
alist[position] = currentvalue
'''
shell 排序
'''
def shell_sort(alist):
sublist_count = len(alist) // 2
while sublist_count > 0:
for startposition in range(sublist_count):
gap_insertion_sort(alist, startposition, sublist_count)
sublist_count = sublist_count // 2
def gap_insertion_sort(alist, start, gap):
for index in range(start, len(alist), gap):
currentvalue = alist[index]
position = index
while position > start and alist[position-gap] > currentvalue:
alist[position] = alist[position-gap]
position = position - gap
alist[position] = currentvalue
'''
归并排序
'''
def merge_sort(alist):
if len(alist) < 2:
return alist
middle = len(alist) // 2
left = merge_sort(alist[:middle])
right = merge_sort(alist[middle:])
return merge(left, right)
def merge(left, right):
i = 0
j = 0
k = 0
result = []
while i < len(left) and j < len(right):
if left[i] < right[j]:
result.append(left[i])
i += 1
else:
result.append(right[j])
j += 1
k += 1
result += right[j:]
result += left[i:]
return result
if __name__ == '__main__':
# print(bubble_sort([]))
# print(bubble_sort([2, 1, 3, 45, 5, 5]))
# print(fast_sort([2, 1, 3, 45, 5, 5]))
# print(fast_sort([2, 2, 2, 2]))
import random
ls = [random.randint(1, 100) for x in range(0, 100)]
# import time
# t1 = time.time()
# stdQuickSort(ls)
# # print(ls)
# t2 = time.time()
# print(t2 - t1)
# selection_sort(ls)
# insertion_sort(ls)
# shell_sort(ls)
print(merge_sort(ls))