151. Reverse Words in a String

Solution:

  • first added the words to a list and joined up the list.
  • the code below is similar except I looped through the string backwards and just appended to the ret string. technically I think this is the same as looping forward and just prepending to the ret string.. but oh well.
class Solution:
    def reverseWords(self, s: str) -> str:
        i = len(s) - 1
        ret = ""
        first = True
        while i >= 0:
            while i >= 0 and s[i] == ' ':
                i -= 1
            j = i - 1
            while j >= 0 and s[j] != ' ':
                j -= 1
            if s[j+1:i+1]:
                if first:
                    first = False
                else:
                    ret += ' '
                ret += s[j+1:i+1]
            i = j - 1
        return ret
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