Reverse Words in a String

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Given an input string s, reverse the order of the words.
给定一个输入字符串 s ，颠倒单词的顺序。

A word is defined as a sequence of non-space characters. The words in s will be separated by at least one space.
单词定义为非空格字符序列。中的 s 字词将至少用一个空格分隔。

Return a string of the words in reverse order concatenated by a single space.
以相反的顺序返回由单个空格连接的单词字符串。

Note that s may contain leading or trailing spaces or multiple spaces between two words. The returned string should only have a single space separating the words. Do not include any extra spaces.
请注意，可能包含 s 前导或尾随空格或两个单词之间的多个空格。返回的字符串应该只有一个空格来分隔单词。不要包含任何多余的空格。

Example 1: 示例 1：

Input: s = "the sky is blue" Output: "blue is sky the"

Example 2: 示例 2：

Input: s = " hello world " Output: "world hello" Explanation: Your reversed string should not contain leading or trailing spaces.

Example 3: 例3：

Input: s = "a good example" Output: "example good a" Explanation: You need to reduce multiple spaces between two words to a single space in the reversed string.

Constraints: 约束：

1 <= s.length <= 104
s contains English letters (upper-case and lower-case), digits, and spaces ' '.
s 包含英文字母（大写和小写）、数字和空格 ' ' 。
There is at least one word in s.
中 s 至少有一个单词。

Follow-up: If the string data type is mutable in your language, can you solve it in-place with O(1) extra space?
跟进：如果字符串数据类型在您的语言中是可变的，你能用额外的空间就 O(1) 地解决它吗？

package org.leetcode;  
  
public class ReverseWordsInString {  
    public String reverseWords(String s) {  
        String[] words = s.split("\\s+");  
  
  
        String[] reversedWords = new String[words.length];  
        for (int i = 0; i < words.length; i++) {  
            reversedWords[i] = words[words.length - 1 - i];  
        }  
  
        String reversedSentence = String.join(" ", reversedWords);  
        // delete the last space  
        return reversedSentence.trim();  
    }  
  
    public static void main(String[] args) {  
        String sentence1 = "The dog is the best";  
        String reversedSentence1 = new ReverseWordsInString().reverseWords(sentence1);  
        System.out.println("Reversed sentence1: " + reversedSentence1); // Expected output: "best the is dog The"  
  
        String sentence2 = "  hello world  ";  
        String reversedSentence2 = new ReverseWordsInString().reverseWords(sentence2);  
        System.out.println("Reversed sentence2: " + reversedSentence2); // Expected output: "full so am I thanksgiving, Happy"  
  
  
        String sentence3 = "a good   example";  
        String reversedSentence3 = new ReverseWordsInString().reverseWords(sentence3);  
        System.out.println("Reversed sentence3: " + reversedSentence3); // Expected output: "example good a"  
    }  
}