Implement atoi to convert a string to an integer.
Hint: Carefully consider all possible input cases. If you want a challenge, please do not see below and ask yourself what are the possible input cases.
Notes: It is intended for this problem to be specified vaguely (ie, no given input specs). You are responsible to gather all the input requirements up front.
题目大意：将字符串转换为整数
解题思路：其实该题的关键是按照所有可能输入的情况分情况讨论，一开始想到的是不合法输入、正负号以及超出整数范围这几种情况，后来运行过后未通过，才发现还应该处理空格、空字符串的情况。
因此，首先用一个变量来保存符号，判断输入的内容是否合法或为空字符串，是就返回0.然后用Python函数strip删除空格，判断符号，最后判断是否超出整数范围。
代码如下：
class Solution(object):
def myAtoi(self, str):
"""
:type str: str
:rtype: int
"""
answer = 0
sign = 1
if str == "" or not str:
return 0
str = str.strip()
if str[0] == '+':
str = str[1:]
elif str[0] == '-':
sign = -1
str = str[1:]
for i in str:
if i >= '0' and i <= '9':
answer = 10 * answer + ord(i) - ord('0')
else:
break
answer = sign * answer
if answer > 2147483647:
answer = 2147483647
elif answer < -2147483648:
answer = -2147483648
return answer