class Solution(object):

    def shipWithinDays(self, weights, D):

        """

        :type weights: List[int]

        :type D: int

        :rtype: int

        """

        l, r, middle = max(weights), sum(weights), 0

        # start the binary search strategy

        while l < r:

            middle = int((l + r) / 2)

            # check whether this capacity(middle value) is best

            days, w = 1, 0

            for i, val in enumerate(weights):

                w += val

                if w > middle:

                    days += 1

                    w = val

            if days > D:

                l = middle + 1

            if days <= D:

                r = middle

        return l