题解 | #表示数值的字符串#

代码非常有条理，不加注释应该页能看懂吧...小数判断会利用到整数判断，科学计数法判断需要用到整数判断和小数判断，所以新建了3个函数。

class Solution:
    def isNumeric(self , str: str) -> bool:
        # write code here
        str = str.strip()
        if str.count('e') + str.count('E') > 1:
            return False
        elif str.count('e') + str.count('E') == 1:
            return self.checkSci(str)
        if str.count('.') > 1:
            return False
        elif str.count('.') == 1:
            return self.checkDeci(str)              
        return self.checkInt(str)
    
    def checkInt(self, str):
        if len(str)>0 and str[0] in ['+','-']:
            str = str[1:]
        if len(str) == 0:
            return False
        for i in str:
            if i not in ['1','2','3','4','5','6','7','8','9','0']:
                return False
        return True
    
    def checkDeci(self, str):
        if len(str)>0 and str[0] in ['+','-']:
            str = str[1:]
        dotPos = str.find('.')
        if dotPos == -1:
            return False
        preStr = str[:dotPos]
        postStr = str[dotPos+1:]
        if self.checkInt(preStr):
            if self.checkInt(postStr) or len(postStr) == 0:
                return True
        if self.checkInt(postStr):
            if len(preStr) == 0:
                return True
        return False
          
    def checkSci(self, str):
        ePos = str.find('e')
        if ePos == -1:
            ePos = str.find('E')
        preStr = str[:ePos]
        postStr = str[ePos+1:]
        if self.checkInt(preStr) or self.checkDeci(preStr):
            if self.checkInt(postStr):
                return True            
        return False