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Author: NinePiece2

Solutions/0919-projection-area-of-3d-shapes/README.md

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+<p>You are given an <code>n x n</code> <code>grid</code> where we place some <code>1 x 1 x 1</code> cubes that are axis-aligned with the <code>x</code>, <code>y</code>, and <code>z</code> axes.</p>
+
+<p>Each value <code>v = grid[i][j]</code> represents a tower of <code>v</code> cubes placed on top of the cell <code>(i, j)</code>.</p>
+
+<p>We view the projection of these cubes onto the <code>xy</code>, <code>yz</code>, and <code>zx</code> planes.</p>
+
+<p>A <strong>projection</strong> is like a shadow, that maps our <strong>3-dimensional</strong> figure to a <strong>2-dimensional</strong> plane. We are viewing the &quot;shadow&quot; when looking at the cubes from the top, the front, and the side.</p>
+
+<p>Return <em>the total area of all three projections</em>.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+<img alt="" src="https://s3-lc-upload.s3.amazonaws.com/uploads/2018/08/02/shadow.png" style="width: 800px; height: 214px;" />
+<pre>
+<strong>Input:</strong> grid = [[1,2],[3,4]]
+<strong>Output:</strong> 17
+<strong>Explanation:</strong> Here are the three projections (&quot;shadows&quot;) of the shape made with each axis-aligned plane.
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<pre>
+<strong>Input:</strong> grid = [[2]]
+<strong>Output:</strong> 5
+</pre>
+
+<p><strong class="example">Example 3:</strong></p>
+
+<pre>
+<strong>Input:</strong> grid = [[1,0],[0,2]]
+<strong>Output:</strong> 8
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>n == grid.length == grid[i].length</code></li>
+	<li><code>1 &lt;= n &lt;= 50</code></li>
+	<li><code>0 &lt;= grid[i][j] &lt;= 50</code></li>
+</ul>

Solutions/0919-projection-area-of-3d-shapes/solution.py

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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