Is Surface Area of 3D Shapes easy or hard?

Surface Area of 3D Shapes is categorized as an Easy problem on LeetCode with an acceptance rate above 70%. The challenge is recognizing how shared faces reduce surface area when stacks touch each other in the grid.

Surface Area of 3D Shapes Python/Java solution

Python and Java implementations follow the same idea: iterate over the grid, add the base contribution for each stack, and subtract overlapping faces with neighbors. The logic fits in a single nested loop and runs in O(m*n) time with constant space.

How to solve Surface Area of 3D Shapes in O(n)?

Treat the grid as a height map and scan each cell once. For every stack with height h, add its contribution and subtract shared faces with adjacent stacks using min(height1, height2). Since each cell is visited exactly once, the total runtime becomes O(m*n).

What is the best approach for Surface Area of 3D Shapes?

The best approach is the direct surface area calculation that subtracts shared faces between adjacent stacks. Iterate through the grid, add the base contribution of each stack (4*h + 2), and subtract overlaps with neighbors using min heights. This runs in O(m*n) time with O(1) extra space.

Is Surface Area of 3D Shapes asked at Google/Amazon/Meta?

Grid traversal and surface counting problems appear frequently in interviews at companies like Amazon and Google because they test spatial reasoning and matrix iteration. While this exact problem may vary, similar geometry-on-grid questions are common.

What data structure is used in Surface Area of 3D Shapes?

The primary data structure is a 2D array (matrix). Each element represents the height of stacked cubes at that position. The algorithm performs simple neighbor comparisons within the matrix.

What is the time complexity of Surface Area of 3D Shapes?

The time complexity is O(m*n), where m and n are the grid dimensions. Each cell is processed once, and only constant-time arithmetic and neighbor checks are performed. Space complexity remains O(1) because no additional data structures are required.

892. Surface Area of 3D Shapes - Practice Online

You are given an n x n grid where you have placed some 1 x 1 x 1 cubes. Each value v = grid[i][j] represents a tower of v cubes placed on top of cell (i, j).

After placing these cubes, you have decided to glue any directly adjacent cubes to each other, forming several irregular 3D shapes.

Return the total surface area of the resulting shapes.

Note: The bottom face of each shape counts toward its surface area.

Example 1:

Input: grid = [[1,2],[3,4]]
Output: 34

Example 2:

Input: grid = [[1,1,1],[1,0,1],[1,1,1]]
Output: 32

Example 3:

Input: grid = [[2,2,2],[2,1,2],[2,2,2]]
Output: 46

Constraints:

n == grid.length == grid[i].length
1 <= n <= 50
0 <= grid[i][j] <= 50