LeetCode刷题笔录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.

这题可以从尾部开始往前扫描，把尾部所有的空格都跳过去，遇到的第一个非空格字符设为end。再从end开始往前扫描，遇到的第一个空格设为start。长度就是end - start。

public class Solution {
    public int lengthOfLastWord(String s) {
        int end = s.length() - 1;
        //search from the end, find the first non-space char
        while(end >= 0 && s.charAt(end) == ' ')
            end--;
        if(end == -1)
            return 0;
        
        int start = end;
        
        while(start >= 0 && s.charAt(start) != ' ')
            start--;
        return end - start;
    }
}