算法图解 1.2 二分查找

1.2 二分查找

仅当列表是有序时，二分查找才管用
例子：
binary_search
书中代码大致如下：

# 二分查找
def binary_search(list, item):
    low = 0
    high = len(list) - 1
    while low <= high:
        """只要范围没有缩小到只含有一个元素，就检查中间的元素"""
        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, 3, 5, 7, 9]
print(binary_search(my_list, 3)) # => 1
print(binary_search(my_list, -1)) # => None

但是，会报错！！
TypeError: list indices must be integers or slices, not float

将其中：mid = (low + high) / 2
改为：mid = int((low + high) / 2)
即可顺利运行