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"

方法：兩次尋找空格。

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

另一種實現：

public class Solution {
    public int lengthOfLastWord(String s) {
        int stop = s.length();
        for(int i = s.length() - 1; i >= 0; i--) {
            if (s.charAt(i) != ' ') break;
            stop = i;
        }
        int start = stop;
        for(int i = start; i > 0; i--) {
            if (s.charAt(i - 1) == ' ') break;
            start = i - 1;
        }
        return stop - start;
    }
}