python：4种基本排序算法
2018-03-13 13:57:38         来源：小沫_jie的博客

## 1.冒泡排序

```# -*- coding:utf-8 -*-

def bubble_sort(A):
for i in range(len(A)-1):  # 决定进行的轮数
for j in range(0, len(A)-i-1):  # 列表下标
if A[j] > A[j+1]:
A[j+1], A[j] = A[j], A[j+1]
return A

A = [0, 5, 4, 3, 2, 1]
print(bubble_sort(A))```

## 2.快速排序

```# -*- coding:utf-8 -*-

def partition(A, low, high):
pivot = A[low]
while low < high:
while low < high and A[high] >= pivot:
high -= 1
A[low] = A[high]
while low < high and A[low] <= pivot:
low += 1
A[high] = A[low]
A[low] = pivot
return low

def quick_sort(A, low, high):
if low < high:
pivot = partition(A, low, high)
print(A, low, high)
quick_sort(A, low, pivot-1)
quick_sort(A, pivot+1, high)
return A

A = [3, 5, 4, 8, 2, 1]
print(quick_sort(A, 0, 5))

```

## 3.归并排序

```# -*- coding:utf-8 -*-

def merge_sort(A):
if len(A) == 1:
return A
mid = len(A)//2
left = merge_sort(A[:mid])
right = merge_sort(A[mid:])

return merge(left, right)

def merge(left, right):
result = []
while len(left) > 0 and len(right) > 0:
if left[0] < right[0]:
result.append(left.pop(0))
else:
result.append(right.pop(0))
result += left
result += right
return  result

A = [3, 5, 4, 8, 2, 1]
print(merge_sort(A))```

## 4. 插入排序

```# -*- coding:utf-8 -*-

def insert_sort(A):
for i in range(1, len(A)):
j = i-1
if A[i] < A[j]:
temp = A[i]
A[i] = A[j]
j = j-1
while j >= 0 and A[j] > temp:
A[j+1] = A[j]
j -= 1
A[j+1] = temp
return A

A = [3, 5, 4, 8, 2, 1]
print(insert_sort(A))```