Package g2401_2500.s2424_longest_uploaded_prefix

Class LUPrefix

java.lang.Object
g2401_2500.s2424_longest_uploaded_prefix.LUPrefix
public class LUPrefix extends java.lang.Object
2424 - Longest Uploaded Prefix.

Medium

You are given a stream of n videos, each represented by a distinct number from 1 to n that you need to “upload” to a server. You need to implement a data structure that calculates the length of the longest uploaded prefix at various points in the upload process.

We consider i to be an uploaded prefix if all videos in the range 1 to i ( inclusive ) have been uploaded to the server. The longest uploaded prefix is the maximum value of i that satisfies this definition.

Implement the LUPrefix class:

  • LUPrefix(int n) Initializes the object for a stream of n videos.
  • void upload(int video) Uploads video to the server.
  • int longest() Returns the length of the longest uploaded prefix defined above.

Example 1:

Input

[“LUPrefix”, “upload”, “longest”, “upload”, “longest”, “upload”, “longest”]

[[4], [3], [], [1], [], [2], []]

Output: [null, null, 0, null, 1, null, 3]

Explanation:

 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.

Constraints:

  • 1 <= n <= 105
  • 1 <= video <= n
  • All values of video are distinct.
  • At most 2 * 105 calls in total will be made to upload and longest.
  • At least one call will be made to longest.

  • Constructor Summary

    Constructors
    Constructor
    Description
    LUPrefix(int n)
     

  • Method Summary

    Modifier and Type
    Method
    Description
    int
    longest()
     
    void
    upload(int video)
     

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Constructor Details

    • LUPrefix

      public LUPrefix(int n)

  • Method Details

    • upload

      public void upload(int video)

    • longest

      public int longest()