Package g2401_2500.s2424_longest_uploaded_prefix

Class LUPrefix

  • public class LUPrefix
extends 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 Detail

      • LUPrefix

        public LUPrefix​(int n)

    • Method Detail

      • upload

        public void upload​(int video)

      • longest

        public int longest()