DAY5：leetcode #8 String to Integer (atoi)

最新推荐文章于 2023-02-25 23:03:36 发布

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最新推荐文章于 2023-02-25 23:03:36 发布

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本文详细解析了atoi函数如何实现字符串到整数的转换，包括空格处理、符号判断、数字识别和范围检查等关键步骤，并提供了一个简化版的实现代码。注意考虑int类型边界情况。

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.

Update (2015-02-10):
The signature of the C++ function had been updated. If you still see your function signature accepts a const char * argument, please click the reload button to reset your code definition.

spoilers alert... click to show requirements for atoi.

Requirements for atoi:

The function first discards as many whitespace characters as necessary until the first non-whitespace character is found. Then, starting from this character, takes an optional initial plus or minus sign followed by as many numerical digits as possible, and interprets them as a numerical value.

The string can contain additional characters after those that form the integral number, which are ignored and have no effect on the behavior of this function.

If the first sequence of non-whitespace characters in str is not a valid integral number, or if no such sequence exists because either str is empty or it contains only whitespace characters, no conversion is performed.

If no valid conversion could be performed, a zero value is returned. If the correct value is out of the range of representable values, INT_MAX (2147483647) or INT_MIN (-2147483648) is returned.

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class Solution(object):
    def myAtoi(self, str):
        """
        :type str: str
        :rtype: int
        """
        try:
            str = str.lstrip()
            for word in 'qwertyuiop[]\\asdfghjkl;\'/.,mnbvcxz!@#$%^&*()QWERTYUIOP{}|ASDFGHJKL:"ZXCVBNM<>? ':
                if word in str:
                    str = str[:str.index(word)]
            i = int(str)
        except ValueError,e:
            return 0
        if i > 2147483647:
            i = 2147483647
        if i < -2147483648:
            i = -2147483648
        return i

比较无聊的一道题，要考虑int越界，左边的空格可以删掉，中间出现不可转int的字符就转换前边的可转一部分。不推荐做。