剑指offer 表示数值的字符串

题目描述

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。

class Solution {
public:
    bool isNumeric(char* string)
    {


int i = 0;
        if(string[i]=='+' || string[i]=='-' || IsNum(string[i])){
            while(string[++i]!='\0' && IsNum(string[i]));
            //后面跟小数点
            if(string[i]=='.'){
                if(IsNum(string[++i])){
                    while(string[++i]!='\0' && IsNum(string[i]));
                    if(string[i]=='e'||string[i]=='E'){
                        i++;
                        if(string[i]=='+' || string[i]=='-' || IsNum(string[i])){
                            while(string[++i]!='\0' && IsNum(string[i]));
                            if(string[i]=='\0') return true;
                            else return false;
                        }else return false;
                    }else if(string[i]=='\0') return true;
                    else return false;
                }else if(string[++i]=='\0') return true;
                else return false;
            }
            //后面跟e或者E
            else if(string[i]=='e'||string[i]=='E'){
                i++;
                if(string[i]=='+' || string[i]=='-' || IsNum(string[i])){
                    while(string[++i]!='\0' && IsNum(string[i]));
                    if(string[i]=='\0') return true;
                    else return false;
                }else return false;
            }
            
            else if(string[i]=='\0') return true;
            else return false;           
        }else return false;
    }
     
    bool IsNum(char ch)
    {
        if(ch<'0'||ch>'9') return false;
        else return true;
    }
        


};