def find(sub_str, target_str):
    """[summary]
    字符串查找

    Arguments:
        sub_str {str} -- substring
        target_str {str} -- target string

    Returns:
        bool -- if substring is found in target string
    """

    return sub_str in target_str
    # in operator用的是Boyer–Moore算法，最坏情况O(mn), 最好情况O(n/m)
    # 速度肯定好过re.search()