Beautiful Arrangement II LeetCode solution in Python

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class Solution:
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    def constructArray(self, n: int, k: int) -> List[int]:
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        # n = 8, k = 5
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        # 1 2 3 8 4 7 5 6
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        # 1 1 5 4 3 2 1
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        res = list(range(1, n - k + 1))
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        sign, val = 1, k
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        for i in range(k):
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            res.append(res[-1] + sign * val)
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            sign *= -1
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            val -= 1
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        return res