题目如下：

解题思路：对于v = grid[i][j]，其表面积为s = 2 + v*4 。接下来只要在判断其相邻四个方向有没有放置立方体，有的话减去重合的面积即可。

代码如下：

class Solution(object):    def surfaceArea(self, grid):        """        :type grid: List[List[int]]        :rtype: int        """        res = 0        for i in range(len(grid)):            for j in range(len(grid[i])):                if grid[i][j] == 0:                    continue                area = 2 + 4 * grid[i][j]                if i-1 >= 0:                    area -= min(grid[i-1][j],grid[i][j])                if j-1 >= 0:                    area -= min(grid[i][j],grid[i][j-1])                if i + 1 < len(grid):                    area -= min(grid[i][j],grid[i+1][j])                if j + 1 < len(grid[i]):                    area -= min(grid[i][j],grid[i][j+1])                res += area        return res