priority-queue

问题 Using Scala 2.9 to implement a kind of Dijkstra algorithm (pseudo code) val queue = new PriorityQueue queue.insert(...) while (!queue.isEmpty) { val u = queue.extractMin queue.foreach { v => if (condition(u, v)) queue.decreaseKey(v, newPriority) } } I'd like to change priority of an item in Scala's collection.mutable.PriorityQueue . Therefore tried to remove item change priority reinsert into queue. But I can't find a method to either update priority or remove a specific item (not necessarily

问题 I try to replace std::multiset with std::priority_queue. But I was dissapointed with the speed results. Running time of the algorithm increase by 50%... Here are the corresponding commands: top() = begin(); pop() = erase(knn.begin()); push() = insert(); I am surprised with the speed of priority_queue implementation, I expected different results (better for PQ)... Conceptually, the multiset is being used as a priority queue. Why are the priority queue and the multiset have such different

问题 How can we use STL priority_queue for struct ? Any illustration of pushing & popping , where struct has multiple data-types? Say : struct thing { int a; char b;} glass[10]; . Now how can i put this struct on priority_queue using 'int a' for ordering ? 回答1: Here is a slightly modified answer to your original question, which you deleted for no apparent reason. The original contained enough information for you to figure this out, but here it goes: provide a less than comparison that uses the int

问题 This question already has answers here : Change priorityQueue to max priorityqueue (14 answers) Closed 3 years ago . The Priority Queue implementation in the Java standard library appears to be a min Priority Queue which I found somewhat confusing. In order to turn it into a max one I created a custom comparator object. Comparator<Integer> cmp = new Comparator<Integer>() { public int compare( Integer x, Integer y ) { return y - x; } }; I was wondering if there was a more elegant solution.

问题 It seems that a priority queue is just a heap with normal queue operations like insert, delete, top, etc. Is this the correct way to interpret a priority queue? I know you can build priority queues in different ways but if I were to build a priority queue from a heap is it necessary to create a priority queue class and give instructions for building a heap and the queue operations or is it not really necessary to build the class? What I mean is if I have a function to build a heap and

问题 Since both std::priority_queue and std::set (and std::multiset ) are data containers that store elements and allow you to access them in an ordered fashion, and have same insertion complexity O(log n) , what are the advantages of using one over the other (or, what kind of situations call for the one or the other?)? While I know that the underlying structures are different, I am not as much interested in the difference in their implementation as I am in the comparison their performance and

问题 In the .NET Framework in PresentationCore.dll, there is a generic PriorityQueue<T> class whose code can be found here. I wrote a short program to test the sorting, and the results weren't great: using System; using System.Collections.Generic; using System.Diagnostics; using MS.Internal; namespace ConsoleTest { public static class ConsoleTest { public static void Main() { PriorityQueue<int> values = new PriorityQueue<int>(6, Comparer<int>.Default); Random random = new Random(88); for (int i =

问题 i am very confused with this little example of java.util.PriorityQueue and my own Comparator: In this code i get a wrong order in the queue. The result is: 5,8,7 instead of 5,7,8 Is there anything wrong with my Comparator<Vertex> ? Thank you for your help. public class Test { public static void main(String[] args) { PriorityQueue<Vertex> priorityQueue = new PriorityQueue<Vertex>(new Comparator() { @Override public int compare(Object o1, Object o2) { Vertex u = (Vertex) o1; Vertex v = (Vertex)

问题 I have a function written using std::multimap which is excruciatingly slow precisely because of the std::multimap . After analysis, I realized that I am only using the std::multimap as a heap , so I am trying to substitute it with a std::priority_queue which only allows for heap operations, in the hope it will be faster for this usage. Of course, the element type of std::priority_queue would need to be std::pair<mmKey, mmValue> , and then I would pass a custom comparator to the std::priority

问题 On the wave of this SO question and with many hints from another one, I'm trying to implement an AsyncTask variant with tasks that can be prioritized. In my CustomAsyncTask class I have: public abstract class CustomAsyncTask<Params, Progress, Result> { private static int CORE_POOL_SIZE = 1; private static int MAXIMUM_POOL_SIZE = 1; private static final int KEEP_ALIVE = 1; private static final ThreadFactory sThreadFactory = new ThreadFactory() { private final AtomicInteger mCount = new