Day020 - 151. Reverse Words in a String

151. 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 <= 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?

내 풀이

class Solution:
    def reverseWords(self, s: str) -> str:
        return ' '.join([i for i in reversed(s.split())])

다른 풀이

class Solution:
    def reverseWords(self, s: str) -> str:
        import re # split 함수 대신 re.split으로 정규표현식으로 제거

        c = re.split(r'\s+', s.strip()) # \s+는 하나 이상의 공백을 의미      
        l = 0
        r = len(c) - 1


        while l < r:
            c[l], c[r] = c[r], c[l]
            l += 1
            r -= 1
        
        result = ' '.join(c)
        return result

# Time Complexity : \(O(N)\)