【LeetCode刷题Java版】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".

click to show clarification.

Clarification:

• What constitutes a word?
  A sequence of non-space characters constitutes a word.
• Could the input string contain leading or trailing spaces?
  Yes. However, your reversed string should not contain leading or trailing spaces.
• How about multiple spaces between two words?
  Reduce them to a single space in the reversed string.

package com.liuhao.acm.leetcode;/** * @author liuhao *  *         Given an input string, reverse the string word by word. For example, *         Given s = "the sky is blue", return "blue is sky the". */public class ReverseWords {public static String reverseWords(String s) {// 若输入字符串直接是空串，则直接返回该字符串if (s.equals("")) {return "";}// 将字符串按空格"\\s{1,}"进行分割，一个或者多个空格的正则："\\s{1,}"String[] strArr = s.split("\\s{1,}");int len = strArr.length;// 分割后字符串变成空串，直接返回if (len == 0) {return "";}// 用StringBuilder更加有效StringBuilder sb = new StringBuilder("");// 反向输出之前分割的字符串数组for (int i = len - 1; i >= 0; i--) {if (!strArr[i].equals("")) {sb.append(strArr[i]);sb.append(" ");}}sb.deleteCharAt(sb.lastIndexOf(" "));return sb.toString();}public static void main(String[] args) {System.out.println(reverseWords(""));}}