python Quicksort demo

__author__ = 'student'

'''

quicksort

step 1, choose one pivot, such as pivot=la[0]

step 2, scan the data from right side, find data less than pivot, then swap this with pivot

pivot=1  [4] 5 7 3 20 9 [j]

then scan from left side, find data greater than pivot, then swap the position j and i

4 [] 7 3 20 9 5

when i>=j then finish one loop. then put the pivot in the i;

 all data are dived by pivot now. left is less than pivot and right are greater than pivot.

think step by step then do it and try something

step 3. then you have two parts to sort, left part and right part.

recursive  call this method to sort

'''

import random

def quicksort(la,l,r):

    if l>=r :

        return

    left=l;right=r

    pivot=la[left]

    while left < right:

        while left<right and la[right]>pivot:

            right-=1

        if left<right :

            la[left]=la[right]

            left+=1

        while left<right and la[left]<pivot:

            left+=1

        if left<right:

            la[right]=la[left]

    la[left]=pivot

    quicksort(la,l,left-1)

    quicksort(la,left+1,r)

def quicksort2(la):

    if len(la)<=1:

        return la

    return quicksort2([lt for lt in la[1:] if lt<la[0]])+ la[0:1]+quicksort2([ge for ge in la[1:] if ge>=la[0]])

import sys

sys.setrecursionlimit(999)

la=[]

def generatenumbers(la,len):

    for x in range(len):

        la.extend([random.randint(1,50)])

generatenumbers(la,1000)

print la

quicksort(la,0,len(la)-1)

print la
巴特西

python Quicksort demo

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