[LeetCode] Length of Last Word

Problem:

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.

Solution1:O(n)

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

Solution2:O(n)

public class Solution {
    public int lengthOfLastWord(String s) {
        String str[] = s.split(" ");
        if(str.length ==0)
            return 0;    
        return str[str.length-1].length();
    }
}