二分查找的最大查找次数及Python实现

一、比较次数

1、如果最多比较x次，则区间长度为2^(x-1) ~ 2^x-1
2、对于区间长度y，最多比较logy+1次

二、python代码：

def binary_search(l1, item):
    low = 0
    high = len(l1) - 1
    while low <= high:
        mid = int((low + high) / 2)
        guess = l1[mid]
        if guess == item:
            return mid
        if guess > item:
            high = mid -1
        else:
            low = mid + 1
    return None


my_list = [1, 3, 5, 7, 9]
print(binary_search(my_list, -1))