July - Day 15 - Reverse Words in a String

Solution.py

# https://leetcode.com/explore/challenge/card/july-leetcoding-challenge/546/week-3-july-15th-july-21st/3391/

class Solution:
  def reverseWords(self, s: str) -> str:
    def reverse(i: int, j: int):
      while i < j:
        s1[i], s1[j] = s1[j], s1[i]
        i += 1
        j -= 1
      
    s1 = list(s)
    reverse(0, len(s1) - 1)
    
    start = 0
    res = []
    
    for i, v in enumerate(s1):
      if v != ' ' and (i == 0 or s1[i - 1] == ' '):
        start = i
      elif v == ' ' and (i > 0 and s1[i - 1] != ' '):
        reverse(start, i - 1)
        res.append(''.join(s1[start : i]))
      if i == len(s1) - 1 and v != ' ':
        reverse(start, i)
        res.append(''.join(s1[start : i + 1]))
        
    return ' '.join(res)