Given an input string s, reverse the order of the words. A word is defined as a sequence of non-space characters. Words in s will be separated by at least one space. The reversed string should not contain leading or trailing spaces. Multiple spaces between two words should be reduced to a single space in the reversed string.

  • Constraints:

    • 1 <= s.length <= 10^4
    • s consists of English letters (lower-case and upper-case), digits, and spaces.
    • s contains at least one word.

  • Example 1:

Input: s = "the sky is blue"
Output: "blue is sky the"
  • Example 2:
Input: s = "  hello world  "
Output: "world hello"

Solution

The most straightforward approach involves standard string manipulation functions available in most programming languages.

  • High-Level Steps:
    1. Clean up spaces: Remove any leading or trailing spaces from the input string. Many languages have a trim() method for this, or their split functions handle it implicitly.
    2. Split into words: Divide the cleaned string into individual words using a space as the delimiter. Be careful to handle cases with multiple spaces between words, which might result in empty strings if not processed correctly (e.g., using a regex split or filtering empty strings after a simple split).
    3. Reverse word order: Reverse the list or array of words.
    4. Join words: Combine the reversed words back into a single string, using a single space as the separator between them.
class Solution:
    def reverseWords(self, s: str) -> str:
        # Step 1 & 2: Clean up spaces and split into words
        # The split() method in Python without arguments handles multiple spaces 
        # and leading/trailing spaces by default, treating any sequence of 
        # whitespace as a single delimiter and not returning empty strings.
        words = s.split()
        
        # Step 3: Reverse the order of words
        words.reverse() # In-place reversal of the list
        
        # Step 4: Join the words back with a single space
        return " ".join(words)

# Example Usage:
# sol = Solution()
# print(sol.reverseWords("the sky is blue"))         # Output: "blue is sky the"
# print(sol.reverseWords("  hello world  "))       # Output: "world hello"
# print(sol.reverseWords("a good   example"))      # Output: "example good a"