Class LUPrefix
java.lang.Object
g2401_2500.s2424_longest_uploaded_prefix.LUPrefix
2424 - Longest Uploaded Prefix.<p>Medium</p>
<p>You are given a stream of <code>n</code> videos, each represented by a <strong>distinct</strong> number from <code>1</code> to <code>n</code> that you need to “upload” to a server. You need to implement a data structure that calculates the length of the <strong>longest uploaded prefix</strong> at various points in the upload process.</p>
<p>We consider <code>i</code> to be an uploaded prefix if all videos in the range <code>1</code> to <code>i</code> ( <strong>inclusive</strong> ) have been uploaded to the server. The longest uploaded prefix is the <strong>maximum</strong> value of <code>i</code> that satisfies this definition.</p>
<p>Implement the <code>LUPrefix</code> class:</p>
<ul>
<li><code>LUPrefix(int n)</code> Initializes the object for a stream of <code>n</code> videos.</li>
<li><code>void upload(int video)</code> Uploads <code>video</code> to the server.</li>
<li><code>int longest()</code> Returns the length of the <strong>longest uploaded prefix</strong> defined above.</li>
</ul>
<p><strong>Example 1:</strong></p>
<p><strong>Input</strong></p>
<p>[“LUPrefix”, “upload”, “longest”, “upload”, “longest”, “upload”, “longest”]</p>
<p>[[4], [3], [], [1], [], [2], []]</p>
<p><strong>Output:</strong> [null, null, 0, null, 1, null, 3]</p>
<p><strong>Explanation:</strong></p>
<pre><code> LUPrefix server = new LUPrefix(4); // Initialize a stream of 4 videos.
server.upload(3); // Upload video 3.
server.longest(); // Since video 1 has not been uploaded yet, there is no prefix.
// So, we return 0.
server.upload(1); // Upload video 1.
server.longest(); // The prefix [1] is the longest uploaded prefix, so we return 1.
server.upload(2); // Upload video 2.
server.longest(); // The prefix [1,2,3] is the longest uploaded prefix, so we return 3.
</code></pre>
<p><strong>Constraints:</strong></p>
<ul>
<li><code>1 <= n <= 10<sup>5</sup></code></li>
<li><code>1 <= video <= n</code></li>
<li>All values of <code>video</code> are <strong>distinct</strong>.</li>
<li>At most <code>2 * 10<sup>5</sup></code> calls <strong>in total</strong> will be made to <code>upload</code> and <code>longest</code>.</li>
<li>At least one call will be made to <code>longest</code>.</li>
</ul>
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Constructor Summary
Constructors -
Method Summary
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Constructor Details
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LUPrefix
public LUPrefix(int n)
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Method Details
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upload
public void upload(int video) -
longest
public int longest()
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