LeetCode-Valid Number

Validate if a given string is numeric.

Some examples:
"0" => true
" 0.1 " => true
"abc" => false
"1 a" => false
"2e10" => true

Note: It is intended for the problem statement to be ambiguous. You should gather all requirements up front before implementing one.

class Solution {
public:
    bool check(string& s,int start,int end,bool allowPoint,bool allowE){
        if(start>end)return false;
        int i=start;
		bool point=allowPoint;
        if(s[i]=='+'||s[i]=='-'||s[i]>='0'&&s[i]<='9'||s[i]=='.'){
            if(s[i]=='+'||s[i]=='-'){
                i++;
                if(i>end)return false;
                if(s[i]>='0'&&s[i]<='9'){i++;}
				else if(s[i]=='.'){
				    if(!allowPoint)return false;
					i++;
					if(i>end)return false;
					if(s[i]>='0'&&s[i]<='9'){i++;}
					else{
						return false;
					}
				}
                else return false;
            }
			else if(s[i]=='.'){
			    if(!allowPoint)return false;
				point=false;
				i++;
				 if(i>end)return false;
				if(s[i]>='0'&&s[i]<='9'){i++;}
                else return false;
			}
        }
        else{
            return false;
        }
        bool number=false;
        for(;i<=end;i++){
            if(s[i]=='.'){
                if(number)return false;
                if(!point)return false;
                else point=false;
            }
            else if(s[i]>='0'&&s[i]<='9'){
                
            }
            else if(s[i]=='e'){
                if(!allowE)return false;
                return check(s,i+1,end,false,false);
            }
            else {
                return false;
            }
        }
        return true;
    }
    bool isNumber(const char *s) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        if(s==NULL)return false;
        string ss(s);
        int start=0,end=ss.length()-1;
        while(ss[start]==' '&&start<ss.length()){
            start++;
        }
        while(ss[end]==' '&&end>=0){
            end--;
        }
        if(start>end)return false;
        return check(ss,start,end,true,true);
    }
};