Withdrawn: 6356745: (coll) Add PriorityQueue(Collection, Comparator)
duke
duke at openjdk.org
Fri Mar 1 00:04:57 UTC 2024
On Mon, 11 Dec 2023 01:28:29 GMT, Valeh Hajiyev <duke at openjdk.org> wrote:
> This commit addresses the current limitation in the `PriorityQueue` implementation, which lacks a constructor to efficiently create a priority queue with a custom comparator and an existing collection. In order to create such a queue, we currently need to initialize a new queue with custom comparator, and after that populate the queue using `addAll()` method, which in the background calls `add()` method (which takes `O(logn)` time) for each element of the collection (`n` times). This is resulting in an overall time complexity of `O(nlogn)`.
>
>
> PriorityQueue<String> pq = new PriorityQueue<>(customComparator);
> pq.addAll(existingCollection);
>
>
> The pull request introduces a new constructor to streamline this process and reduce the time complexity to `O(n)`. If you create the queue above using the new constructor, the contents of the collection will be copied (which takes `O(n)` time) and then later `heapify()` operation (Floyd's algorithm) will be called once (another `O(n)` time). Overall the operation will be reduced from `O(nlogn)` to `O(2n)` -> `O(n)` time.
>
>
> PriorityQueue<String> pq = new PriorityQueue<>(existingCollection, customComparator);
This pull request has been closed without being integrated.
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PR: https://git.openjdk.org/jdk/pull/17045
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