Length of Last Word

Given a string s consists of some words separated by spaces, return the length of the last word in the string. If the last word does not exist, return 0.

    int lengthOfLastWord(string s) {
       int ans=0;
        for(int i=s.length()-1;i>=0;i--)
        {
            if(s[i]==' ' && ans>0) return ans;
            if(s[i]!=' ' )ans++;
        }
        return ans;
        
    }

  int lengthOfLastWord(string s) {
       int len = 0, tail = s.length() - 1;
        while (tail >= 0 && s[tail] == ' ') tail--;
        while (tail >= 0 && s[tail] != ' ') {
            len++;
            tail--;
        }
        return len;
        
    }