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919. Projection Area Of 3d Shapes

Array Math Geometry Matrix

Problem - Projection Area Of 3d Shapes

Easy

You are given an n x n grid where we place some 1 x 1 x 1 cubes that are axis-aligned with the x, y, and z axes.

Each value v = grid[i][j] represents a tower of v cubes placed on top of the cell (i, j).

We view the projection of these cubes onto the xy, yz, and zx planes.

A projection is like a shadow, that maps our 3-dimensional figure to a 2-dimensional plane. We are viewing the "shadow" when looking at the cubes from the top, the front, and the side.

Return the total area of all three projections.

 

Example 1:

Input: grid = [[1,2],[3,4]]
Output: 17
Explanation: Here are the three projections ("shadows") of the shape made with each axis-aligned plane.

Example 2:

Input: grid = [[2]]
Output: 5

Example 3:

Input: grid = [[1,0],[0,2]]
Output: 8

 

Constraints:

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

Solutions

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class Solution:
    def projectionArea(self, grid: List[List[int]]) -> int:
        xy = sum(val > 0 for row in grid for val in row)
        yz = sum(max(row) for row in grid)
        zx = sum(max(col) for col in zip(*grid))
        return xy + yz + zx

Submission Stats:

  • Runtime: 0 ms (100.00%)
  • Memory: 18.1 MB (18.23%)