151. Reverse Words in a String

• python3

Problem

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?

Pseudocode

1. 양 옆 공백 제거
2. 공백 기준 문자열을 리스트로 만들기
3. 리스트를 거꾸로 루프 돌려서 붙이기

Code

class Solution:
    def reverseWords(self, s: str) -> str:
        s = s.strip()
        sList = s.split();
        result = ""

        for i in range(len(sList)-1, -1, -1):
            result+= sList[i]
            if i != 0:
                result += " "
        
        return result

Result