二分查找算法

注意：二分查找算法针对的是有序的数据集

__author__ = "PoHu"
__copyright__ = "PoHu 2018"
__version__ = "1.0.0"
__license__ = "Henu"


# 今天给大家介绍一个最简单的算法：二分查找算法
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, 3, 5, 7, 9]
print(binary_search(my_list, 3))
print(binary_search(my_list, -1))