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class Solution:
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    def split(self, s: str, delimiter=" ") -> List[str]:
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        start, end = 0, 0
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        res = []
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        for ch in s:
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            if ch == delimiter:
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                if start == end:
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                    start += 1
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                else:
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                    res.append(s[start:end])
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                    start = end + 1
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            end += 1
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        if start != end:
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            res.append(s[start:end])
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        return res
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    def reverse_list(self, ll: List[str]) -> List[str]:
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        l, r = 0, len(ll) - 1
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        while l < r:
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            ll[l], ll[r] = ll[r], ll[l]
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            l += 1
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            r -= 1
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        return ll
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    def reverseWords(self, s: str) -> str:
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        # split first
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        splitted_str_list = self.split(s)
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        # reverse splitted list
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        reversed_str_list = self.reverse_list(splitted_str_list)
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        # join an return
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        return " ".join(reversed_str_list)