Delivering Boxes from Storage to Ports LeetCode solution in Python

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from sortedcontainers import SortedList as MonoQueue
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class Solution:
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    def boxDelivering(self, A, __, B, W):
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        n = len(A)
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        def slidingWindow():
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            l = 0
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            cW = 0
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            for r in range(n):
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                cW += A[r][1]
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                while cW > W or r - l + 1 > B:
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                    cW -= A[l][1]
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                    l += 1
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                yield l, r
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        Seg = MonoQueue(key=lambda t: t[1])
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        addAll = 0
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        olddp = 0
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        for l, r in slidingWindow():
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            if r != 0:
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                addAll += A[r][0] != A[r - 1][0]
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            Seg.add((r, olddp - addAll + 2))
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            while Seg[0][0] < l:
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                Seg.pop(0)
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            olddp = Seg[0][1] + addAll
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        return olddp