String to Integer (atoi)(python)

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本文介绍了一种将字符串转换为整数的方法，并考虑了多种可能的输入情况，包括空格处理、符号判断、溢出检查等。同时给出了具体的实现代码。

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.
注意如果超出范围就返回最接近的 int 数。eg:2147483648 大于 INT_MAX(2147483647) ，就返回 2147483647 。
要注意几点：跳过前面的空格,\t,\n;范围界定

class Solution:

    # @return an integer
    def myAtoi(self, str):
        str = str.strip()
        if not str:
            return 0

        MAX_INT = 2147483647
        MIN_INT = -2147483648
        ret = 0
        overflow = False
        pos = 0
        sign = 1

        if str[pos] == '-':
            pos += 1
            sign = -1
        elif str[pos] == '+':
            pos += 1

        for i in range(pos, len(str)):
            if not str[i].isdigit():
                break
            ret = ret * 10 + int(str[i])
            if not MIN_INT <= sign * ret <= MAX_INT:
                overflow = True
                break

        if overflow:
            return MAX_INT if sign == 1 else MIN_INT
        else:

return sign * ret