source: branches/HeuristicLab.Problems.GrammaticalOptimization-gkr/HeuristicLab.Common/Heap.cs @ 13037

// http://stackoverflow.com/questions/102398/priority-queue-in-net/13776636#13776636


using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System;

public abstract class Heap<T> : IEnumerable<T> {
  private const int InitialCapacity = 0;
  private const int GrowFactor = 2;
  private const int MinGrow = 1;

  private int _capacity = InitialCapacity;
  private T[] _heap = new T[InitialCapacity];
  private int _tail = 0;

  public int Count { get { return _tail; } }
  public int Capacity { get { return _capacity; } }

  protected Comparer<T> Comparer { get; private set; }
  protected abstract bool Dominates(T x, T y);

  protected Heap()
    : this(Comparer<T>.Default) {
  }

  protected Heap(Comparer<T> comparer)
    : this(Enumerable.Empty<T>(), comparer) {
  }

  protected Heap(IEnumerable<T> collection)
    : this(collection, Comparer<T>.Default) {
  }

  protected Heap(IEnumerable<T> collection, Comparer<T> comparer) {
    if (collection == null) throw new ArgumentNullException("collection");
    if (comparer == null) throw new ArgumentNullException("comparer");

    Comparer = comparer;

    foreach (var item in collection) {
      if (Count == Capacity)
        Grow();

      _heap[_tail++] = item;
    }

    for (int i = Parent(_tail - 1); i >= 0; i--)
      BubbleDown(i);
  }
  protected Heap(Heap<T> original) {
    // clone;
    this._capacity = original._capacity;
    this._tail = original._tail;
    this._heap = new T[original._heap.Length];
    Array.Copy(original._heap, this._heap, this._heap.Length);
    this.Comparer = original.Comparer;
  }

  public void Add(T item) {
    if (Count == Capacity)
      Grow();

    _heap[_tail++] = item;
    BubbleUp(_tail - 1);
  }

  private void BubbleUp(int i) {
    if (i == 0 || Dominates(_heap[Parent(i)], _heap[i]))
      return; //correct domination (or root)

    Swap(i, Parent(i));
    BubbleUp(Parent(i));
  }

  public T GetMin() {
    if (Count == 0) throw new InvalidOperationException("Heap is empty");
    return _heap[0];
  }

  public T ExtractDominating() {
    if (Count == 0) throw new InvalidOperationException("Heap is empty");
    T ret = _heap[0];
    _tail--;
    Swap(_tail, 0);
    BubbleDown(0);
    return ret;
  }

  private void BubbleDown(int i) {
    int dominatingNode = Dominating(i);
    if (dominatingNode == i) return;
    Swap(i, dominatingNode);
    BubbleDown(dominatingNode);
  }

  private int Dominating(int i) {
    int dominatingNode = i;
    dominatingNode = GetDominating(YoungChild(i), dominatingNode);
    dominatingNode = GetDominating(OldChild(i), dominatingNode);

    return dominatingNode;
  }

  private int GetDominating(int newNode, int dominatingNode) {
    if (newNode < _tail && !Dominates(_heap[dominatingNode], _heap[newNode]))
      return newNode;
    else
      return dominatingNode;
  }

  private void Swap(int i, int j) {
    T tmp = _heap[i];
    _heap[i] = _heap[j];
    _heap[j] = tmp;
  }

  private static int Parent(int i) {
    return (i + 1) / 2 - 1;
  }

  private static int YoungChild(int i) {
    return (i + 1) * 2 - 1;
  }

  private static int OldChild(int i) {
    return YoungChild(i) + 1;
  }

  private void Grow() {
    int newCapacity = _capacity * GrowFactor + MinGrow;
    var newHeap = new T[newCapacity];
    Array.Copy(_heap, newHeap, _capacity);
    _heap = newHeap;
    _capacity = newCapacity;
  }

  public IEnumerator<T> GetEnumerator() {
    return _heap.Take(Count).GetEnumerator();
  }

  IEnumerator IEnumerable.GetEnumerator() {
    return GetEnumerator();
  }
}

public class MaxHeap<T> : Heap<T> {
  public MaxHeap()
    : this(Comparer<T>.Default) {
  }

  public MaxHeap(Comparer<T> comparer)
    : base(comparer) {
  }

  public MaxHeap(IEnumerable<T> collection, Comparer<T> comparer)
    : base(collection, comparer) {
  }

  public MaxHeap(IEnumerable<T> collection)
    : base(collection) {
  }
  public MaxHeap(MaxHeap<T> original) : base(original) { }

  protected override bool Dominates(T x, T y) {
    return Comparer.Compare(x, y) >= 0;
  }
}

public class MinHeap<T> : Heap<T> {
  public MinHeap()
    : this(Comparer<T>.Default) {
  }

  public MinHeap(Comparer<T> comparer)
    : base(comparer) {
  }

  public MinHeap(IEnumerable<T> collection)
    : base(collection) {
  }

  public MinHeap(IEnumerable<T> collection, Comparer<T> comparer)
    : base(collection, comparer) {
  }
  public MinHeap(MinHeap<T> original) : base(original) { }

  protected override bool Dominates(T x, T y) {
    return Comparer.Compare(x, y) <= 0;
  }
}