python快速排序，合并排序，二分查找

Posted 2021-04-06 中学生大课堂

def quick_sort(alist,start,end):

    left=start
    right=end
    mid=alist[start]

    while left < right:
        while left<right and alist[right]>=mid:
            right -=1
        alist[left]=alist[right]

        while left<right and alist[left]<mid:
            left +=1
        alist[right]=alist[left]

    alist[left]=mid

    quick_sort(alist,start,left-1)
    quick_sort(alist,left+1,end)

def merge_sort(alist):

    if len(alist)==1:
        return alist

    mid=len(alist)//2
    left=alist[:mid]
    right=alist[mid:]

    ll=merge_sort(left)
    rl=merge_sort(right)

    return merge(ll,rl)

def merge(left,right):
    result=[]
    while len(left)>0 and len(right)>0:
        if left[0]<=right[0]:
            result.append(left.pop(0))
        else:
            result.append(right.pop(0))

    result+=left
    result+=right
    return result

def bin_search(alist,item):
    n=len(alist)
    if n==0:
        return False
    mid=n//2
    if alist[mid]==item:
        return True
    elif alist[mid]<item:
        return bin_search(alist[:mid],item)
    else:
        return bin_search(alist[mid+1:],item)



if __name__ == '__main__':
    alist=[1,12,43,5,2,55]
    print(alist)
    #quick_sort(alist,0,len(alist)-1)
    print(alist)

    print("merge")
    alist = [1, 12, 43, 5, 2, 55]
    print(alist)
    list2=merge_sort(alist)
    print(list2)

    print("bin")
    alist = [1, 12, 43, 5, 2, 55]
    print(bin_search(alist,55))