表示数值的字符串

请实现一个函数用来判断字符串是否表示数值（包括整数和小数）。

例如，字符串"+100","5e2","-123","3.1416"和"-1E-16"都表示数值。

但是"12e","1a3.14","1.2.3","+-5"和"12e+4.3"都不是。

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37

class Solution { public:     bool isNumber(string s) {         int i = 0;         while (i < s.size() && s[i] == ' ') i ++ ;         int j = s.size() - 1;         while (j >= 0 && s[j] == ' ') j -- ;         if (i > j) return false;         s = s.substr(i, j - i + 1);           if (s[0] == '-' || s[0] == '+') s = s.substr(1);         if (s.empty() || s[0] == '.' && s.size() == 1) return false;           int dot = 0, e = 0;         for (int i = 0; i < s.size(); i ++ )         {             if (s[i] >= '0' && s[i] <= '9');             else if (s[i] == '.')             {                 dot ++ ;                 if (e || dot > 1) return false;             }             else if (s[i] == 'e' || s[i] == 'E')             {                 e ++ ;                 if (i + 1 == s.size() || !i || e > 1 || i == 1 && s[0] == '.') return false;                 if (s[i + 1] == '+' || s[i + 1] == '-')                 {                     if (i + 2 == s.size()) return false;                     i ++ ;                 }             }             else return false;         }         return true;     } };