Sync LeetCode submission Runtime - 18 ms (67.27%), Memory - 31.1 MB (22.17%)

Author: jimit105

1909-buildings-with-an-ocean-view/README.md

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+<p>There are <code>n</code> buildings in a line. You are given an integer array <code>heights</code> of size <code>n</code> that represents the heights of the buildings in the line.</p>
+
+<p>The ocean is to the right of the buildings. A building has an ocean view if the building can see the ocean without obstructions. Formally, a building has an ocean view if all the buildings to its right have a <strong>smaller</strong> height.</p>
+
+<p>Return a list of indices <strong>(0-indexed)</strong> of buildings that have an ocean view, sorted in increasing order.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> heights = [4,2,3,1]
+<strong>Output:</strong> [0,2,3]
+<strong>Explanation:</strong> Building 1 (0-indexed) does not have an ocean view because building 2 is taller.
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<pre>
+<strong>Input:</strong> heights = [4,3,2,1]
+<strong>Output:</strong> [0,1,2,3]
+<strong>Explanation:</strong> All the buildings have an ocean view.
+</pre>
+
+<p><strong class="example">Example 3:</strong></p>
+
+<pre>
+<strong>Input:</strong> heights = [1,3,2,4]
+<strong>Output:</strong> [3]
+<strong>Explanation:</strong> Only building 3 has an ocean view.
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= heights.length &lt;= 10<sup>5</sup></code></li>
+	<li><code>1 &lt;= heights[i] &lt;= 10<sup>9</sup></code></li>
+</ul>

1909-buildings-with-an-ocean-view/solution.py

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+# Approach 3: Monotonic Stack Space Optimization
+
+# Time: O(n)
+# Space: O(1)
+
+class Solution:
+    def findBuildings(self, heights: List[int]) -> List[int]:
+        n = len(heights)
+        answer = []
+        max_height = -1
+
+        for current in reversed(range(n)):
+            if heights[current] > max_height:
+                answer.append(current)
+                max_height = heights[current]
+
+        answer.reverse()
+        return answer
+