:orphan:

Reverse Words In A String
=========================

.. highlight:: none

Problem
-------
https://leetcode.com/problems/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 <= 10``\ :sup:```4```
- ``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?

.. highlight:: python

Pattern
-------
Two Pointers, String

Solution
--------
Use the built in Python functions for strings ``split`` to split the string,
``reversed`` to reverse the list, and ``join`` to join the list back into a
string.

Code
----

.. literalinclude:: ../problems/medium/reverse-words-in-a-string/reverse_words_in_a_string__approach_1.py
    :language: python
    :lines: 12-

Test
----
>>> from reverse_words_in_a_string__approach_1 import reverseWords
>>> reverseWords('the sky is blue')
'blue is sky the'
>>> reverseWords('  hello world  ')
'world hello'
>>> reverseWords('a good   example')
'example good a'

Complexity
----------
| :math:`n` is the length of the input string
| Time: :math:`O(n)` — split the string and reverse
| Auxiliary Space: :math:`O(`1`)`

.. autofunction:: reverse_words_in_a_string__approach_1.reverseWords