Sword Finger Offer Interview Question 20. A string representing a numeric value [medium]

Interview Question 20. A string representing a numeric value

This example is disgusting

Only spaces-false

Only a decimal point-false (use bool num to determine whether a number appears)

Can be a space at the end

The decimal point can be at the 1st place and the decimal point can be at the end. . .

This question has been submitted more than a dozen times, because of the boundary conditions of these spicy chickens

class Solution {
public:
    bool isNumber(string s) {
        if(s.empty())   return false;
        int e=-1;
        while(s[0]==' '){
            s.erase(0,1);
        }
        while(1){
            int j=s.size()-1;
            if(j>=0&&s[j]==' '){   
                s.erase(j,1);
            }
            else break;
        }
        if(s.empty()) return false;
        bool point=false;
        bool num=false;

        int n=s.size();
        for(int i=0;i<n;i++){
            if(s[i]=='+'||s[i]=='-'){
                if(i!=e+1)  return false;
            }
            else if(s[i]=='.'){
                if(point || e!=-1 ) return false;
                point=true;
            }
            else if(s[i]=='e'){
                if(!num || e!=-1)   return false;
                num=false;
                e=i;
            }
            else if(s[i]<'0' || s[i]>'9')    return false;
            else num=true;
        }
        return num;

    }
};