算法图解——第一章 算法简介

二分查找每次都取中间那个元素跟需要查找的元素比较，返回要查找的元素在列表中的位置
python代码如下：

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

my_list = [1,2,3,4,5,6,7]
print (binary_search(my_list,5))