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.
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\nImplement 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.\n
Example 1:
\n\n\nInput\n["LUPrefix", "upload", "longest", "upload", "longest", "upload", "longest"]\n[[4], [3], [], [1], [], [2], []]\nOutput\n[null, null, 0, null, 1, null, 3]\n\nExplanation\nLUPrefix server = new LUPrefix(4); // Initialize a stream of 4 videos.\nserver.upload(3); // Upload video 3.\nserver.longest(); // Since video 1 has not been uploaded yet, there is no prefix.\n // So, we return 0.\nserver.upload(1); // Upload video 1.\nserver.longest(); // The prefix [1] is the longest uploaded prefix, so we return 1.\nserver.upload(2); // Upload video 2.\nserver.longest(); // The prefix [1,2,3] is the longest uploaded prefix, so we return 3.\n\n\n
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Constraints:
\n\n1 <= n <= 1051 <= video <= nvideo are distinct.2 * 105 calls in total will be made to upload and longest.longest.Compiled with clang 11 using the latest C++ 20 standard.
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