I started learning about Java Stream, and I am wondering is it possible to only peek the first element of the stream without retrieving it. For example, I have multiple streams, and each of them have integers that are sorted in non-decreasing order, and I want to get a sorted list of all integers, so I’m thinking about using a
Tag: priority-queue
Java – Use PriorityQueue sort list but have empty list
This is my solution for leetcode 759. Employee Free Time, but it has index out of boundary issue that i don’t understand. I got “index 0 out of bounds for length 0” exception. The test case i used is ‘[[[1,2]],[[1,3]],[[4,10]]]’ and this is the output: I only have 3 lists and based on the output, it looks like it has
Is there any efficient algorithm for traversing a Heap-Based Priority Queue?
I have implemented a Heap-Based Priority Queue in Java but my challenge now is implementing an efficient Iterator that has a definite (increasing or decreasing) order of traversal. Is there any algorithm that does this at constant auxiliary space and time complexity of O(n)? The O(nlogn) is quite trivial. Also, there is absolutely no subtlety in O(n) space algorithm. Please
Java PriorityQueue: how to heapify a Collection with a custom Comparator?
For example, given a List of Integer List<Integer> list = Arrays.asList(5,4,5,2,2), how can I get a maxHeap from this List in O(n) time complexity? The naive method: However, the time complexity is O(nlogn). We can trigger the heapify method by using the following constructor: The time complexity is O(n). However, it forces me to use the natural order which is
Is PriorityQueue a FIFO Queue?
PriorityQueue implements Queue, but is PriorityQueue a FIFO data structure like Queue? Answer From the Queue interface: Queues typically, but do not necessarily, order elements in a FIFO (first-in-first-out) manner. Among the exceptions are priority queues, which order elements according to a supplied comparator, or the elements’ natural ordering So PriorityQueue is an exception and it becomes a FIFO queue
Change priorityQueue to max priorityqueue
I have priority queue in Java of Integers: When I call pq.poll() I get the minimum element. Question: how to change the code to get the maximum element? Answer How about like this: The Collections.reverseOrder() provides a Comparator that would sort the elements in the PriorityQueue in a the oposite order to their natural order in this case.