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?