58. Length of Last Word

class Solution {
public:
    int lengthOfLastWord(string s) {
        int n=s.size();
        int i=n-1,j;
        while(i>=0&&s[i]==' ')
        {
            i--;
        }
        j=i;
        while(j>=0&&s[j]!=' ')
        {
            j--;
        }
        return i-j;
    }
};