Reverse Words in a String

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： 把string以空格为间隔分隔开存入array, 然后倒着加入stringBuilder并且每个加入以后后面加空格，最后记的清除最后一个空格。

public class Solution {
   public String reverseWords(String s) {
        if (s == null || s.length() == 0) {
            return "";
        }

        String[] array = s.split(" ");
        StringBuilder sb = new StringBuilder();

        for (int i = array.length - 1; i >= 0; i--) {
            if (!array[i].equals("")) {
                sb.append(array[i]).append(" ");
            }
        }

        //remove the last " "
        return sb.length() == 0 ? "" : sb.substring(0, sb.length() - 1);
    }
}