[ckw]

My slow solution:

  class Solution:
    def trap(self, height: List[int]) -> int:
      l,r,s = [*accumulate(height,max),[*accumulate(height[::-1],max)],len(height)
      return sum(max(0, min(l[i], r[s-i-1])-height[i]) for i in range(s))