python Quicksort demo

標籤：

__author__ = ‘student‘‘‘‘quicksortstep 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 pivotpivot=1  [4] 5 7 3 20 9 [j]then scan from left side, find data greater than pivot, then swap the position j and i4 [] 7 3 20 9 5when 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 somethingstep 3. then you have two parts to sort, left part and right part.recursive  call this method to sort‘‘‘import randomdef 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 syssys.setrecursionlimit(999)la=[]def generatenumbers(la,len):    for x in range(len):        la.extend([random.randint(1,50)])generatenumbers(la,1000)print laquicksort(la,0,len(la)-1)print la

python Quicksort demo