Valid Number

class Solution {
public:
    bool isNumber(string s) {
        string num = s;  
        int i=0;  
        while(num[i]==‘ ‘)i++;  
        if(num[i]==‘-‘ || num[i]==‘+‘)i++;  
        int j=num.size()-1;  
        while(num[j]==‘ ‘)j--;  
        if(i<=j)  
            num = num.substr(i,j-i+1);  
        else return false;  
  
        int dot = -1;  
        int ee = -1;  
        for(int i=0; i<num.size(); i++)  
        {  
            if(dot == -1 && num[i] == ‘.‘)  
                dot = i;  
            else if(ee == -1 && num[i] == ‘e‘){  
                ee = i;  
                if(num[i+1] == ‘-‘ || num[i+1]==‘+‘)  
                    i++;  
            }  
            else{   
                int tmpnum = num[i]-‘0‘;  
                if(0<=tmpnum && tmpnum<=9)continue;  
                else return false;  
            }  
        }  
        //xxx.xxexx  
        string startstr,midstr,laststr;  
        if(dot==-1 && ee==-1){//xxxx  
            startstr = num;  
            if(startstr.size()<1)return false;  
        }else if(dot!=-1 && ee==-1){//xxx.xxx  
            startstr = num.substr(0,dot);  
            midstr=num.substr(dot+1);//.1,2.,0.1,0.0,2.0  
            if(startstr.size()<1 && midstr.size()<1)  
                return false;  
        }else if(dot==-1 && ee!=-1){//xxxexxx  
            startstr = num.substr(0,ee);  
            if(startstr.size()<1)return false;  
            if(num[ee+1] == ‘-‘ || num[ee+1]==‘+‘)  
                laststr = num.substr(ee+2);  
            else  
                laststr = num.substr(ee+1);  
            if(laststr.size()<1)return false;  
        }else{//xxx.xxexx  
            if(dot>ee)return false;  
            startstr = num.substr(0,dot);  
            midstr=num.substr(dot+1,ee-dot-1);  
            if(startstr.size()<1 && midstr.size()<1)  
                return false;  
            if(num[ee+1] == ‘-‘ || num[ee+1]==‘+‘)  
                laststr = num.substr(ee+2);  
            else  
                laststr = num.substr(ee+1);  
            if(laststr.size()<1)return false;  
        }  
        return true;  
    }
};