Maximum Product Difference Between Two Pairs — Python

# Time:  O(n)
# Space: O(1)

class Solution(object):
    def maxProductDifference(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        largest, smallest = [0]*2, [float("inf")]*2
        for x in nums:
            if x >= largest[0]:
                largest[:] = [x, largest[0]]
            elif x > largest[1]:
                largest[1] =x
            if x <= smallest[0]:
                smallest[:] = [x, smallest[0]]
            elif x < smallest[1]:
                smallest[1] = x
        return largest[0]*largest[1] - smallest[0]*smallest[1]