排序算法python实现

参考java版的算法书，使用python重写了一遍。初学，自己写的，代码比较粗糙，意思明白就好。 末尾补上了字符串排序和python封装好的排序函数用法

import numpy as np
import random
####验证排序算法是否正确
a=[x for x in range(35)]
random.shuffle(a)
print(a)
rank(a)  ###rank为主函数
print(a)

接下来是不同算法实现

def exch(a,i,j):
        t=a[j]
        a[j]=a[i]
        a[i]=t
####冒泡
def rank(a):
    for i in range(len(a)-1):
        for j in range(i+1,len(a)):
            if a[i]>a[j]:
                exch(a,i,j)
    return a
#####选择排序
def rank(a):
    for i in range(len(a)-1):
        flag=i
        for j in range(i+1,len(a)):
            if a[flag]>a[j]:
                flag=j
        if flag!=i:
           exch(a,i,flag)
    return a
###########插入排序
def rank(a):
    for i in range(1,len(a)):
        j=i
        while j>0 and a[j]<a[j-1]:
            exch(a,j,j-1)
            j-=1
    return a

#######归并排序
def rank(a):
    rankhelper(a,0,len(a)-1)
def rankhelper(a,lo,hi):
    if hi<=lo:
        return
    mid=int((hi-lo)/2+lo)
    rankhelper(a,lo,mid)
    rankhelper(a, mid + 1,hi)
    merg(a,lo,mid,hi)
def merg(a,lo,mid,hi):

    i=lo
    j=mid+1
    result=np.ones(len(a),dtype=int)  ####建空数组会降低排序效率，待改进
    result[lo:hi+1]=a[lo:hi+1]

    for k in range(lo,hi+1):
        if i>mid:
            a[k]=result[j]
            j+=1
        elif j>hi:
            a[k]=result[i]
            i+=1
        elif result[i]<result[j]:
            a[k]=result[i]
            i+=1
        else:
            a[k]=result[j]
            j+=1

####快排
def rank(a):
    random.shuffle(a)
    rankhelper(a,0,len(a)-1)
def rankhelper(a,lo,hi):
    if lo>=hi:
        return
    j=partition(a,lo,hi)
    rankhelper(a,lo,j-1)
    rankhelper(a,j+1,hi)
def partition(a,lo,hi):
    l1=lo+1
    l2=hi
    while True:
        while a[l1]<a[lo]:
            if l1==hi:
                break
            l1+=1
        while a[l2]>a[lo]:
            if l2==lo:
                break
            l2-=1
        if l1>=l2:
            break
        exch(a,l1,l2)
    exch(a,lo,l2)
    return l2

#############堆排序

def sink(a,k,l):   #####最小堆
    while 2*k+1<=l:
        j=2*k+1
        if j<l and a[j]>a[j+1]:
            j=j+1
        if a[j]>a[k]:
            break
        exch(a,j,k)
        k=j
def sink1(a,k,l):  ###最大堆
    while 2*k+1<=l:
        j=2*k+1
        if j<l and a[j]<a[j+1]:
            j+=1
        if a[j]<a[k]:
            break
        exch(a,j,k)
        k=j
def rank(a):
    l=len(a)-1
    t=int(l/2)+1
    while t>=0:
        sink(a,t,l)
        t-=1
    while l>0:
        exch(a,l,0)
        l-=1
        sink(a,0,l)

 字符串排序 高位优先及低位优先。其中字符串排序可以和以上排序算法结合，比如和快排

'''def rank(s):   #########低位优先
    n=len(s) ###字符串数量
    l=len(s[0])-1 ###长度
    temp=[0]*len(s)  ###临时数组
    while l>=0:
        count=[0]*257 ###计数数组
        for i in s:
            count[ord(i[l])+1]+=1   ###每个字符计数
        for j in range(256):
            count[j+1]+=count[j]
        for k in range(n):
            temp[count[ord(s[k][l])]]=s[k]  ####将原数组按顺序呢放入到新数组中
            count[ord(s[k][l])]+=1  #####顺序后移1
        for t in range(n):
            s[t]=temp[t]
        l-=1'''

############高位优先排序
def rank(s):
    rankhelper(s,0,len(s)-1,0)

def rankhelper(s,lo,hi,d): ####引入count[1]即为长度为d的字符串数量，如果字符串长度相同，下一轮迭代count[0]==count[1]将不再递归下去
    count=[0]*258
    temp=[0]*len(s)
    if lo>=hi:
        return
    for i in range(lo,hi+1):
        count[chartAt(s[i],d)+2]+=1
    for j in range(257):
        count[j+1]+=count[j]
    for k in range(lo,hi+1):
        temp[count[chartAt(s[k],d)+1]]=s[k]
        count[chartAt(s[k], d) + 1]+=1
    for l in range(lo,hi+1):
        s[l]=temp[l-lo]
    for r in range(256):
        rankhelper(s,lo+count[r],lo+count[r+1]-1,d+1)


def chartAt(s,d):
    if d<len(s):
        return ord(s[d])
    else:
        return -1

s1='qwertyuiopasdfghjklzxcvbnm1234567890'
s=[]
for i in range(10):
    #s.append(''.join(random.sample(s1,6)))  ###低位优先生成长度一致的字符
    s.append(''.join(random.sample(s1,int(random.randint(2,8))))) ###高位优先自动生成字符串
print(s)
rank(s)
print(s)

之后就是封装好的函数sorted使用了 python3 取消了cmp，感觉不是很灵活，自定义函数有点麻烦 python3 3个参数，list（可迭代对象）key 函数定义，按值或按键，reverse 升序或降序

import random

###s生成随机字典
keys=[]
for i in range(10):
    keys.append(random.randint(1,100))
values=[]
s1='qwertyuiopasdfghjklzxcvbnm1234567890'
for j in range(10):
    values.append(''.join(random.sample(s1,int(random.randint(2,5)))))

list1={key:value for key,value in zip(keys,values)}

print(list1)
####排序主体
t1=sorted(list1) ###对键排序
t2=sorted(list1.values()) ##对值排序
t3=sorted(list1.items(),key=lambda x:x[0]) ###按键排序并返回字典
t4=sorted(list1.items(),key=lambda x:x[1]) ###按值排序并返回字典
print(t1)
print(t2)
print(t3)
print(t4)