Leetcode 58 Length of Last Word

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.

Solution 1: Count from end

 public class Solution {  
   public int lengthOfLastWord(String s) {  
     int n=s.length();  
     int i=n-1;  
     while (i>=0 && s.charAt(i)==' ') i--;  
     if (i<0) return 0;  
     int j=i;  
     while (j>=0 && s.charAt(j)!=' ') j--;  
     return i-j;  
   }  
 }