Create README - LeetHub

Author: hogan-tech

3531-count-covered-buildings/README.md

@@ -0,0 +1,83 @@
+<h2><a href="https://leetcode.com/problems/count-covered-buildings">3819. Count Covered Buildings</a></h2><h3>Medium</h3><hr><p>You are given a positive integer <code>n</code>, representing an <code>n x n</code> city. You are also given a 2D grid <code>buildings</code>, where <code>buildings[i] = [x, y]</code> denotes a <strong>unique</strong> building located at coordinates <code>[x, y]</code>.</p>
+
+<p>A building is <strong>covered</strong> if there is at least one building in all <strong>four</strong> directions: left, right, above, and below.</p>
+
+<p>Return the number of <strong>covered</strong> buildings.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<p><img src="https://assets.leetcode.com/uploads/2025/03/04/telegram-cloud-photo-size-5-6212982906394101085-m.jpg" style="width: 200px; height: 204px;" /></p>
+
+<div class="example-block">
+<p><strong>Input:</strong> <span class="example-io">n = 3, buildings = [[1,2],[2,2],[3,2],[2,1],[2,3]]</span></p>
+
+<p><strong>Output:</strong> <span class="example-io">1</span></p>
+
+<p><strong>Explanation:</strong></p>
+
+<ul>
+	<li>Only building <code>[2,2]</code> is covered as it has at least one building:
+
+	<ul>
+		<li>above (<code>[1,2]</code>)</li>
+		<li>below (<code>[3,2]</code>)</li>
+		<li>left (<code>[2,1]</code>)</li>
+		<li>right (<code>[2,3]</code>)</li>
+	</ul>
+	</li>
+	<li>Thus, the count of covered buildings is 1.</li>
+</ul>
+</div>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<p><img src="https://assets.leetcode.com/uploads/2025/03/04/telegram-cloud-photo-size-5-6212982906394101086-m.jpg" style="width: 200px; height: 204px;" /></p>
+
+<div class="example-block">
+<p><strong>Input:</strong> <span class="example-io">n = 3, buildings = [[1,1],[1,2],[2,1],[2,2]]</span></p>
+
+<p><strong>Output:</strong> <span class="example-io">0</span></p>
+
+<p><strong>Explanation:</strong></p>
+
+<ul>
+	<li>No building has at least one building in all four directions.</li>
+</ul>
+</div>
+
+<p><strong class="example">Example 3:</strong></p>
+
+<p><img src="https://assets.leetcode.com/uploads/2025/03/16/telegram-cloud-photo-size-5-6248862251436067566-x.jpg" style="width: 202px; height: 205px;" /></p>
+
+<div class="example-block">
+<p><strong>Input:</strong> <span class="example-io">n = 5, buildings = [[1,3],[3,2],[3,3],[3,5],[5,3]]</span></p>
+
+<p><strong>Output:</strong> <span class="example-io">1</span></p>
+
+<p><strong>Explanation:</strong></p>
+
+<ul>
+	<li>Only building <code>[3,3]</code> is covered as it has at least one building:
+
+	<ul>
+		<li>above (<code>[1,3]</code>)</li>
+		<li>below (<code>[5,3]</code>)</li>
+		<li>left (<code>[3,2]</code>)</li>
+		<li>right (<code>[3,5]</code>)</li>
+	</ul>
+	</li>
+	<li>Thus, the count of covered buildings is 1.</li>
+</ul>
+</div>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>2 &lt;= n &lt;= 10<sup>5</sup></code></li>
+	<li><code>1 &lt;= buildings.length &lt;= 10<sup>5</sup> </code></li>
+	<li><code>buildings[i] = [x, y]</code></li>
+	<li><code>1 &lt;= x, y &lt;= n</code></li>
+	<li>All coordinates of <code>buildings</code> are <strong>unique</strong>.</li>
+</ul>