waterfill.py

class Solution(object):
    def trap(self, height):
        """
        :type height: List[int]
        :rtype: int
        """
        water = 0
        height_len = len(height)
        if height_len < 3:
            return water

        max_level = max(height)
        max_level_index = height.index(max_level)

        prev_level = height[0]
        for x in range(max_level_index):
            level = height[x]

            if level < prev_level and level < max_level:
                water += (prev_level - level)
            else:
                prev_level = level

        prev_level = height[-1]
        for x in range(height_len-1, max_level_index, -1):
            level = height[x]

            if level < prev_level and level < max_level:
                water += (prev_level - level)
            else:
                prev_level = level

        return water