第八题：字符串转整数。

def myAtoi(s):
    """

    :type s: str
    :return: int
    """


    s = s.strip(‘ ‘)
    if len(s) == 0:
        return  0
    flag = 0
    rel = 0
    if s[0] == ‘-‘:
        flag =1
        s = s.split(‘-‘)[1]
    elif s[0] == ‘+‘:
        s = s.split(‘+‘)[1]
    nums = ‘0123456789‘
    for each in s:
        if each in nums:
            rel = rel*10+int(each)
        else:
            break
    if flag == 1:
        rel = -rel
    if rel > pow(2,31)-1:
        return pow(2,31)-1
    if rel < -pow(2,31):
        return -pow(2,31)
    return rel