数据结构面试中经常会被问到篇排序相关的问题，那么这篇文章会研究下怎么用python来实现排序。

冒泡排序

#coding：utf-8

# 冒泡排序
def maopao():
    a = [2,1,4,3,9,5,6,8,7]
    for i in range(len(a)-1):
        for j in range(len(a)-1-i):
            if a[j]>a[j+1]:
                temp = a[j]
                a[j] = a[j+1]
                a[j+1] = temp
    print(a)
maopao()

结果为：

[1, 2, 3, 4, 5, 6, 7, 8, 9]

归并排序

# 归并排序
def merge(a,b):
    i,j = 0,0
    c = []
    while i<=len(a)-1 and j<=len(b)-1:
        if a[i]<b[j]:
            c.append(a[i])
            i+=1
        else:
            c.append(b[j])
            j+=1
    if i<=len(a)-1:
        for m in a[i:]:
            c.append(m)
    
    if j<=len(b)-1:
        for n in b[j:]:
            c.append(n)
    return c

def guibing(a):
    if len(a)<=1:
        return a
    center = int(len(a)/2)
    left = guibing(a[:center])
    right = guibing(a[center:])
    return merge(left,right)

print(guibing([2,1,4,3,9,5,6,8,7]))

结果为：

[1, 2, 3, 4, 5, 6, 7, 8, 9]

#　快速排序

#　快速排序    
def kpsort(left,right,a):
    based = a[left]
    i = left
    j = right
    while i < j:
        # 从数组右边开始遍历
        while a[j]>=based and i<j:
            j -= 1
        a[i] = a[j]
        while a[i]<=based and i<j:
            i += 1
        
        a[j]= a[i]
        a[i] = based

    return i
    
def kuaipai(left,right,a):
    if left<right:
        p = kpsort(left,right,a)
        kuaipai(left,p-1,a)
        kuaipai(p+1,right,a)

    return a
            
print(kuaipai(0,8,a =[2,1,4,3,9,5,6,8,7]))

结果为

[1, 2, 3, 4, 5, 6, 7, 8, 9]