Python基础第十二天：二分法算法

二分法查找算法

　　如果有这样一个列表，让你从这个列表中找到66的位置，你要怎么办？

　　l = [2,3,5,10,15,16,18,22,26,30,32,35,41,42,43,55,56,66,67,69,72,76,82,83,88]

　　

　　实现

l = [2,3,5,10,15,16,18,22,26,30,32,35,41,42,43,55,56,66,67,69,72,76,82,83,88,89]
l.sort()
def func(l,aim):
    if len(l) == 0:
        print("not find")
        return
    index = (len(l)-1)//2
    if aim > l[index]:
        func(l[index+1:],aim)
    elif aim < l[index]:
        func(l[:index-1],aim)
    elif aim == l[index]:
        print('find ', aim)
    else:
        print("not find")

func(l,31)

not find

l = [2,3,5,10,15,16,18,22,26,30,32,35,41,42,43,55,56,66,67,69,72,76,82,83,88,89]
l.sort()
def search(num,l,start=None,end=None):
    start = start if start else 0
    end = end if end else len(l) - 1
    mid = (end - start)//2 + start
    
    if start > end:
        return None
    elif l[mid] > num :
        return search(num,l,start,mid-1)
    elif l[mid] < num:
        return search(num,l,mid+1,end)
    elif l[mid] == num:
        return mid

print(search(31,l))

None