Reverse words in a string

Problem Description

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: 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.

Examples

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 <= 10^4
• 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?

Code Template

class Solution:
    def reverseWords(self, s: str) -> str:
        # Write your code here
        pass

Solutions

• Solution 1: This approach manually parses the string to collect words, reverses their order, and joins them with a single space. It has a time complexity of O(n) and space complexity of O(n).

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