042 Trapping Rain Water

class Solution:
    # @param {integer[]} height
    # @return {integer}
    def trap(self, height):
        stack = []
        ans = 0
        i, length = 0, len(height)
        while i < length:
            if stack == []:
                stack.append([height[i], 1])
            else:
                if height[i] < stack[-1][0]:
                    stack.append([height[i], 1])
                else:
                    if height[i] >= stack[0][0]:
                        hh = stack[0][0]
                        while stack != []:
                            col = stack.pop()
                            h = col[0]
                            l = col[1]
                            ans += (hh - h) * l
                        stack.append([height[i], 1])
                    else:
                        tmp = 1
                        hh = height[i]
                        while hh >= stack[-1][0]:
                            col = stack.pop()
                            h = col[0]
                            l = col[1]
                            ans += (hh - h) * l
                            tmp += l
                        stack.append([hh, tmp])
            i += 1
        return ans