我正在寻找优先级队列或堆数据结构的.NET实现
Priority queues are data structures that provide more flexibility than simple sorting, because they allow new elements to enter a system at arbitrary intervals. It is much more cost-effective to insert a new job into a priority queue than to re-sort everything on each such arrival.
The basic priority queue supports three primary operations:
Insert(Q,x). Given an item x with key k, insert it into the priority queue Q.
Find-Minimum(Q). Return a pointer to the item
whose key value is smaller than any other key in the priority queue
Q.
Delete-Minimum(Q). Remove the item from the priority queue Q whose key is minimum
除非我找错地方了，否则框架里没有。有谁知道好的吗，还是我自己卷?
这是我刚刚写的一个，也许它没有那么优化(只是使用了一个排序的字典)，但很容易理解。
您可以插入不同类型的对象，因此没有泛型队列。
using System;
using System.Diagnostics;
using System.Collections;
using System.Collections.Generic;
namespace PrioQueue
{
public class PrioQueue
{
int total_size;
SortedDictionary<int, Queue> storage;
public PrioQueue ()
{
this.storage = new SortedDictionary<int, Queue> ();
this.total_size = 0;
}
public bool IsEmpty ()
{
return (total_size == 0);
}
public object Dequeue ()
{
if (IsEmpty ()) {
throw new Exception ("Please check that priorityQueue is not empty before dequeing");
} else
foreach (Queue q in storage.Values) {
// we use a sorted dictionary
if (q.Count > 0) {
total_size--;
return q.Dequeue ();
}
}
Debug.Assert(false,"not supposed to reach here. problem with changing total_size");
return null; // not supposed to reach here.
}
// same as above, except for peek.
public object Peek ()
{
if (IsEmpty ())
throw new Exception ("Please check that priorityQueue is not empty before peeking");
else
foreach (Queue q in storage.Values) {
if (q.Count > 0)
return q.Peek ();
}
Debug.Assert(false,"not supposed to reach here. problem with changing total_size");
return null; // not supposed to reach here.
}
public object Dequeue (int prio)
{
total_size--;
return storage[prio].Dequeue ();
}
public void Enqueue (object item, int prio)
{
if (!storage.ContainsKey (prio)) {
storage.Add (prio, new Queue ());
}
storage[prio].Enqueue (item);
total_size++;
}
}
}
AlgoKit
我写了一个名为AlgoKit的开源库，可以通过NuGet获得。它包含:
隐式d-ary堆(ArrayHeap)，
二项堆,
配对堆。
代码已经经过了广泛的测试。我强烈建议你试一试。
例子
var comparer = Comparer<int>.Default;
var heap = new PairingHeap<int, string>(comparer);
heap.Add(3, "your");
heap.Add(5, "of");
heap.Add(7, "disturbing.");
heap.Add(2, "find");
heap.Add(1, "I");
heap.Add(6, "faith");
heap.Add(4, "lack");
while (!heap.IsEmpty)
Console.WriteLine(heap.Pop().Value);
为什么有三堆?
实现的最佳选择强烈依赖于输入-正如Larkin, Sen和Tarjan在优先队列的回归基础经验研究中所显示的，arXiv:1403.0252v1 [cs.DS]。他们测试了隐式d-ary堆、配对堆、斐波那契堆、二项式堆、显式d-ary堆、排名配对堆、震动堆、违反堆、排名放松的弱堆和严格斐波那契堆。
AlgoKit具有三种类型的堆，在测试中似乎是最有效的。
关于选择的提示
对于数量相对较少的元素，您可能会对使用隐式堆感兴趣，特别是第四元堆(隐式4元)。在操作较大堆大小的情况下，像二项式堆和配对堆这样的平摊结构应该执行得更好。
