ReverseWordsInAString

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?

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.

Pattern

Two Pointers, String

Code

def reverseWords(s: str) -> str:
    """Reverse the words in a string, separated by 1 space.
    """
    words = s.strip().split()
    return ' '.join(reversed(words))

Test

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

ReverseWordsInAString.reverseWords(s: str) → str

Reverse the words in a string, separated by 1 space.