Python常用排序算法实例

Python几个常用排序算法实例例如直接插入排序、直接选择排序、冒泡排序、快速排序等。 

下面用Python实现了几个常用的排序，如快速排序，选择排序，以及二路并归排序等等。

#encoding=utf-8

# www.jbxue.com

import random

from copy import copy

def directInsertSort(seq):

""" 直接插入排序 """

size = len(seq)

for i in range(1,size):

tmp, j = seq[i], i

while j > 0 and tmp < seq[j-1]:

seq[j], j = seq[j-1], j-1

seq[j] = tmp

return seq

def directSelectSort(seq):

""" 直接选择排序 """

size = len(seq)

for i in range(0,size - 1):

k = i;j = i+1

while j < size:

if seq[j] < seq[k]:

k = j

j += 1

seq[i],seq[k] = seq[k],seq[i]

return seq

def bubbleSort(seq):

"""冒泡排序"""

size = len(seq)

for i in range(1,size):

for j in range(0,size-i):

if seq[j+1] < seq[j]:

seq[j+1],seq[j] = seq[j],seq[j+1]

return seq

def _divide(seq, low, high):

"""快速排序划分函数"""

tmp = seq[low]

while low != high:

while low < high and seq[high] >= tmp: high -= 1

if low < high:

seq[low] = seq[high]

low += 1

while low < high and seq[low] <= tmp: low += 1

if low < high:

seq[high] = seq[low]

high -= 1

seq[low] = tmp

return low

def _quickSort(seq, low, high):

"""快速排序辅助函数"""

if low >= high: return

mid = _divide(seq, low, high)

_quickSort(seq, low, mid - 1)

_quickSort(seq, mid + 1, high)

def quickSort(seq):

"""快速排序包裹函数"""

size = len(seq)

_quickSort(seq, 0, size - 1)

return seq

def merge(seq, left, mid, right):

tmp = []

i, j = left, mid

while i < mid and j <= right:

if seq[i] < seq[j]:

tmp.append(seq[i])

i += 1

else:

tmp.append(seq[j])

j += 1

if i < mid: tmp.extend(seq[i:])

if j <= right: tmp.extend(seq[j:])

seq[left:right+1] = tmp[0:right-left+1]

def _mergeSort(seq, left, right):

if left == right: 

return

else:

mid = (left + right) / 2

_mergeSort(seq, left, mid)

_mergeSort(seq, mid + 1, right)

merge(seq, left, mid+1, right)

#二路并归排序

def mergeSort(seq):

size = len(seq)

_mergeSort(seq, 0, size - 1)

return seq

if __name__ == '__main__':

s = [random.randint(0,100) for i in range(0,20)]

print s

print "\n"

print directSelectSort(copy(s))

print directInsertSort(copy(s))

print bubbleSort(copy(s))

print quickSort(copy(s))

print mergeSort(copy(s))

运行结果：

E:\python_project\practice>sorting.py
[10, 47, 56, 76, 64, 84, 26, 8, 47, 51, 88, 81, 32, 95, 91, 29, 28, 69, 61, 45]

[8, 10, 26, 28, 29, 32, 45, 47, 47, 51, 56, 61, 64, 69, 76, 81, 84, 88, 91, 95]
[8, 10, 26, 28, 29, 32, 45, 47, 47, 51, 56, 61, 64, 69, 76, 81, 84, 88, 91, 95]
[8, 10, 26, 28, 29, 32, 45, 47, 47, 51, 56, 61, 64, 69, 76, 81, 84, 88, 91, 95]
[8, 10, 26, 28, 29, 32, 45, 47, 47, 51, 56, 61, 64, 69, 76, 81, 84, 88, 91, 95]
[8, 10, 26, 28, 29, 32, 45, 47, 47, 51, 56, 61, 64, 69, 76, 81, 84, 88, 91, 95]