python基础--二分查找

二分法算法代码(不用递归,春算法)

lst=[1,2,3,4,5,6,7,8,9,10,62,87,95,410,456,567,894,999]
n=894
left = 0
right = len(lst)-1
count=0
while left<=right:
    middle = (left+right)//2
    if n<lst[middle]:
        right=middle-1
    elif n>lst[middle]:
        left=middle+1
    else:
        print("计算了%d次"%count)
        print("n的位置在",middle)
        break
    count+=1
else:
    print("不存在")

二分算法递归1

lst = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 62, 87, 95, 410, 456, 567, 894, 999]


def binary_search(left, right, n):
    middle = (left + right) // 2
    if left > right:
        return -1
    if n > lst[middle]:
        left = middle + 1
    elif n < lst[middle]:
        right = middle - 1
    else:
        return middle
    return binary_search(left, right, n)


print(binary_search(0, len(lst) - 1, 45))

二分算法递归2

lst=[1,2,3,4,5,6,7,8,9,10,62,87,95,410,456,567,894,999]
def binary_search(lst,n):
    left = 0
    right = len(lst)-1
    mid = (left+right)//2
    if right <=0:
        print("不存在")
        return -1
    if n>lst[mid]:
        lst = lst[mid+1:]
    elif n<lst[mid]:
        lst = lst[:mid]
    else :
        print("存在")
        return -1
    binary_search(lst,n)
binary_search(lst,1000)