剑指offer54 表示数值的字符串

错误的代码：

class Solution {
public:
    bool isNumeric(char* string)
    {
        if(string == NULL)
            return false;
        if(*string == '+' || *string == '-')
            string++;
        if(*string == '')
            return false;
        bool flag = true;
        ScanDigit(string);
        if(*string != ''){
            if(*string == '.'){
                string++;
                ScanDigit(string);
                if(*string == 'e' || *string == 'E')
                    flag = Exponential(string+1);
            }
            else if(*string == 'e' || *string == 'E')
                flag = Exponential(string+1);
            else
                flag = false;
        }
        return flag && (*string == '');
    }
    void ScanDigit(char *string){
        while(*string >= '0' && *string <= '9' && *string != '')
            string++;
    }
    bool Exponential(char *string){
        if(*string == '+' || *string == '-')
            string++;
        if(*string == '')
            return false;
        ScanDigit(string);
        if(*string == '')
            return true;
        else
            return false;
    }
};