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.

这一题很简单，但是有一个地方很无聊。 就是可能在一个word之后有很多空格，但是当你要得到last word length的时候 是要忽略这些空格的。 所以首先除去末尾的空格。

public class Solution {
    public int lengthOfLastWord(String s) {
        // Note: The Solution object is instantiated only once and is reused by each test case.
        if(s == null || s.length() == 0) return 0;
        int i = 0;
        int tail = 0;
        for(;tail < s.length(); tail ++){
            if(s.charAt(s.length() - tail - 1) != ' ') break;
        }
        while(i < s.length() - tail)
        {
            if(s.charAt(s.length() - tail - i - 1) == ' ') return i;
            i ++;
        }
        return s.length() - tail;
    }
}

第三遍：

public class Solution {
    public int lengthOfLastWord(String s) {
        if(s == null || s.length() == 0) return 0;
        int right = s.length() - 1;
        while(right > -1 && s.charAt(right) == ' ') right --;
        int left = right;
        while(left > -1 && s.charAt(left) != ' ') left --;
        return right - left;
    } 
}