Reverse Words in a String

Given an input string `s`, reverse the order of the **words**. A **word** is defined as a sequence of non-space characters. The **words** in `s` will be separated by at least one space. Return _a string of the words in reverse order concatenated by a single space._ 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.   **Example 1:** **Input:** s = "the sky is blue" **Output:** "blue is sky the" ``` **Example 2:** **Input:** s = " hello world " **Output:** "world hello" **Explanation:** Your reversed string should not contain leading or trailing spaces. ``` **Example 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:** - `1 <= s.length <= 104` - `s` contains English letters (upper-case and lower-case), digits, and spaces `' '`. - There is **at least one** word in `s`.   Follow-up: If the string data type is mutable in your language, can you solve it in-place with `O(1)` extra space?