Given a string s consists of upper/lower-case alphabets and empty space characters ' ', return the length of last word in the string. If the last word does not exist, return 0.

Note: A word is defined as a character sequence consists of non-space characters only.

For example, Given s = "Hello World",return 5.

class Solution {
public:
    int lengthOfLastWord(string s) {
        if(s.size() <= 0) return 0;
        int r = s.size() - 1, b=0, e=0;
        while(r >= 0){
            if(s[r] != ' ') break;
            else r-=1;
        }
        e = r;
        while(r >= 0){
            if(s[r] == ' ') break;
            else r-=1;
        }
        b = r;
        return e - b;
    }
};