Capacity To Ship Packages Within D Days LeetCode solution in Python

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# Runtime: 1388 ms (Top 11.51%) | Memory: 17.1 MB (Top 35.27%)
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class Solution:
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    def shipWithinDays(self, weights: List[int], days: int) -> int:
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        def calc(m):  # function calculate no of days for given weight
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            c, s = 0, 0
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            for i in weights:
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                if i + s > m:
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                    c += 1
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                    s = 0
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                s += i
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            if s > 0:
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                c += 1
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            return c
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        left, right = max(weights), sum(weights)
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        while left <= right:
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            mid = (left + right) // 2
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            if calc(mid) > days:
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                left = mid + 1
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            else:
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                right = mid - 1
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        return left