题目：

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.

思路：

• 题意：给定一个字符串，每个单词用“ ”隔开，求最后一个单词的长度，如果没有返回0
• 利用String.split(” “),分开成String数组，返回最后衣字符串的长度，考虑输入的字符串s为null，s= “ ”，s=“hello ”（以空格结尾）

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代码：

public class Solution {
    public int lengthOfLastWord(String s) {
        if(s == null){
            return 0;
        }
        String[] ss = s.split(" ");
        int n = ss.length;
        if(n < 1){
            return 0;
        }
        String a = ss[n-1];
        if(a == null){
            return 0;
        }
        char[] aa = a.toCharArray();
        return aa.length;
    }
}