02 查找 – 二分查找

# 针对有序列表
def binary_search(lst, value):
    left = 0
    right = len(lst) - 1
    while left <= right:
        mid = (left + right) // 2
        if lst[mid] == value:
            return mid
        elif lst[mid] > value:
            right = mid - 1
        else:
            left = mid + 1
    else:
        return None