bx02_linear&binary_search

def linear_search(li, val):

    for index, v in enumerate(li):
        if v == val:
            return index
        return None


def binary_search(li, val):

    left, right = 0, len(li) - 1

    # 候选区有值
    while left <= right:
        mid = (left + right) // 2
        if li[mid] == val:
            return mid
        # 待查找的值在 mid 左侧
        elif li[mid] > val:
            right = mid - 1
        # 待查找的值在 mid 右侧
        else:
            left = mid + 1
    return None


li = [1,2,3,4,5,6,7,8,9]
print(binary_search(li, 3))