常用排序算法的Python实现

最近一段时间学习了python，发现python真是个强大，强大到和Matlab相媲美。为了熟悉python，将之前的各种排序算法用python实现了一下。

常用的时间复杂度为O(n^2)的排序算法有冒泡排序，插入排序和选择排序，时间复杂度为O(nlog2(n))的算法有快速排序，归并排序和堆排序，

这里的快速排序的初始比较值partition是随机给定的，在用python进行编写时能更清楚的理解整个排序算法的过程。

import random
def BubbleSort(num):
    n=len(num)
    for i in range(0,n):
        for j in range(i,n):
            if num[i]>=num[j]:
                num[i],num[j]=num[j],num[i]
    return num
def SelectSort(num):
    for i in range(0,len(num)):
        mindex=i
        for j in range(i,len(num)):
            if num[mindex]>num[j]:
                mindex=j
        num[mindex],num[i]=num[i],num[mindex]
    return num
def InsertSort(num):
    for i in range(1,len(num)):
        j=i-1
        tmp=num[i]
        while j>0 and tmp<num[j]:
            num[j+1]=num[j]
            j-=1
        num[j]=tmp
    return num
def MergerSort(num):
    if len(num)<=1:
        return num
    left=MergerSort(num[:len(num)/2])
    right=MergerSort(num[len(num)/2:])
    result=[]
    while len(left)>0 and len(right)>0:
        if left[0]>right[0]:
            result.append(right.pop(0))
        else:
            result.append(left.pop(0))
    if len(left)>0:
        result.extend(MergerSort(left))
    else:
        result.extend(MergerSort(right))
    return result
def QuickSort(num):
    if len(num)<=1:
        return num
    greater=[]
    less=[]
    p=num.pop(random.randint(0,len(num)-1))
    for item in num:
        if item < p:
            less.append(item)
        else:
            greater.append(item)
    return QuickSort(less)+[p]+QuickSort(greater)
############################################################
def InsertIntoHeap(x,heap):
    if len(heap)==0:
        heap=[x]
        return heap
    heap.append(x)
    pos=len(heap)
    while True:
        if pos==1:
            return heap
        father=pos/2
        if heap[father-1]<heap[pos-1]:
            heap[father-1],heap[pos-1]=heap[pos-1],heap[father-1]
            pos=father
        else:
            return heap
def CreateHeap(x):
    b=[]
    for i in x:
        InsertIntoHeap(i,b)
    return b 
def HandHeap(a):
    if a==None or type(a)!=list:
        return 
    if a==[] or len(a)==1:
        return a 
    pos=0
    while True:
        if 2*(pos+1)>len(a):
            return a 
        if 2*(pos+1)==len(a):
            if a[pos]<a[2*pos+1]:
                a[pos],a[2*pos+1]=a[2*pos+1],a[pos]
            return a 
        if 2*(pos+1)+1<=len(a):
            if a[pos]<a[2*pos+1]and a[2*pos+1]>=a[2*pos+2]:  
                a[pos],a[2*pos+1]=a[2*pos+1],a[pos]  
                pos=2*pos+1  
            elif a[pos]<a[2*pos+2]and a[2*pos+1]<a[2*pos+2]:  
                a[pos],a[2*pos+2]=a[2*pos+2],a[pos]  
                pos=2*pos+2  
            else:  
                return a 
def HeapSort(num):
    if num==None or type(num)!=list:
        return 
    b=CreateHeap(num)
    a=[]
    while b:
        a.append(b[0])
        b[0]=b[len(b)-1]
        b.pop()
        b=HandHeap(b)
    return a
    

接下来学习python的面向对象编程。