[LeetCode] 186. Reverse Words in a String II

 Problem : https://leetcode.com/problems/reverse-words-in-a-string-ii/

This problem requests reverse words in place.

So we reverse the entire list first, then reverse every words again.

class Solution:
    def reverseWords(self, s: List[str]) -> None:
        """
        Do not return anything, modify s in-place instead.
        """
    
        def reverse(left, right):
            while left < right:
                s[left], s[right] = s[right], s[left]
                left += 1
                right -= 1
        
        
        reverse(0, len(s) - 1)
        
        left = 0
        for right in range(len(s)):
            if s[right] == ' ':
                reverse(left, right -1)
                left = right + 1
        
        # revese the last word
        reverse(left, len(s) -1)