Given an input string, reverse the string word by word.

For example,

Given s = "the sky is blue",
return "blue is sky the".

思路

用stack 或者 遍历时从后往前遍历

注意

给定的string可能是由多个空格隔开的，直接用slipt(" ")会得到[, , , a, , , b]，不是我们想要的。
必须用s.split("\\s+")这样split多个空格

public class Solution {
    public String reverseWords(String s) {
        if (s == null || s.length() == 0) {
            return s;
        }
        
        //split by multiple space
        String[] temp = s.split("\\s+");
        System.out.print(Arrays.toString(temp));
        StringBuilder result = new StringBuilder();
        
        for (int i = temp.length - 1; i >= 0; i--) {
            result.append(temp[i]).append(" ");
        }
        
        String res = result.toString();
        
        return res.trim();
    }
}