Leetcode 65. Valid Number

最新推荐文章于 2021-06-21 17:15:44 发布

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本文深入探讨了如何通过Python编程语言来判断一个给定的字符串是否可以被解析为一个有效的浮点数。文章详细解释了浮点数的构成规则，包括小数点、指数符号‘e’以及正负号的位置限制，并提供了一个完整的代码示例。

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s=s.strip() delete the space front and end.
‘e’ can only appear after digits and ‘.’ cannot appear after ‘e’. In other words, the character before ‘e’ and after ‘e’ must be both digits. (e3 and 3e are both invalid)
‘+’ and ‘-‘ can only be the first character of the string or the next character of ‘e’.
‘.’ can appear only one time and before e.

class Solution:
    def isNumber(self, s):
        """
        :type s: str
        :rtype: bool
        """
        s = s.strip()
        isDot, isDigit, isE = False, False, False
        
        for i, x in enumerate(s):
            if x=='e':
                if not isDigit or isE:
                    return False
                isDigit=False
                isE=True
            elif x in "+-":
                if not i==0 and not s[i-1]=='e':
                    return False
            elif x=='.':
                if isDot or isE:
                    return False
                isDot=True
            elif x.isdecimal():
                isDigit=True
            else:
                return False
        return isDigit