Minimum Number of Swaps to Make the Binary String Alternating LeetCode solution in Python

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class Solution:
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    def minSwaps(self, st: str) -> int:
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        def swap(st, c):
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            n = len(st)
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            mis = 0
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            for i in range(n):
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                if i % 2 == 0 and st[i] != c:
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                    mis += 1
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                if i % 2 == 1 and st[i] == c:
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                    mis += 1
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            return mis // 2
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        dic = Counter(st)
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        z = dic["0"]
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        o = dic["1"]
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        res = 0
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        if abs(z - o) > 1:
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            return -1
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        elif z > o:
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            res = swap(st, "0")
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        elif o > z:
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            res = swap(st, "1")
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        else:
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            res = min(swap(st, "0"), swap(st, "1"))
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        return res