trap rain water

class Solution(object):
    def trap(self, height):
        """
        :type height: List[int]
        :rtype: int
        """
        if height is None or not height:
            return 0

        left = 0
        right = len(height) - 1

        cur_max_left = 0
        cur_max_right = 0

        result = 0

        while right >= left:
            if height[left] <= height[right]:
                if height[left] > cur_max_left:
                    cur_max_left = height[left]
                result += max(cur_max_left - height[left], 0)
                left += 1
            else:
                if height[right] > cur_max_right:
                    cur_max_right = height[right]
                result += max(cur_max_right - height[right], 0)
                right -= 1

        return result