[12876] | 1 | // http://stackoverflow.com/questions/102398/priority-queue-in-net/13776636#13776636
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| 2 |
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| 3 |
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| 4 | using System.Collections;
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| 5 | using System.Collections.Generic;
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| 6 | using System.Linq;
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| 7 | using System;
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| 8 |
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| 9 | public abstract class Heap<T> : IEnumerable<T> {
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| 10 | private const int InitialCapacity = 0;
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| 11 | private const int GrowFactor = 2;
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| 12 | private const int MinGrow = 1;
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| 13 |
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| 14 | private int _capacity = InitialCapacity;
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| 15 | private T[] _heap = new T[InitialCapacity];
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| 16 | private int _tail = 0;
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| 17 |
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| 18 | public int Count { get { return _tail; } }
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| 19 | public int Capacity { get { return _capacity; } }
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| 20 |
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| 21 | protected Comparer<T> Comparer { get; private set; }
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| 22 | protected abstract bool Dominates(T x, T y);
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| 23 |
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| 24 | protected Heap()
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| 25 | : this(Comparer<T>.Default) {
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| 26 | }
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| 27 |
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| 28 | protected Heap(Comparer<T> comparer)
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| 29 | : this(Enumerable.Empty<T>(), comparer) {
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| 30 | }
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| 31 |
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| 32 | protected Heap(IEnumerable<T> collection)
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| 33 | : this(collection, Comparer<T>.Default) {
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| 34 | }
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| 35 |
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| 36 | protected Heap(IEnumerable<T> collection, Comparer<T> comparer) {
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| 37 | if (collection == null) throw new ArgumentNullException("collection");
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| 38 | if (comparer == null) throw new ArgumentNullException("comparer");
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| 39 |
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| 40 | Comparer = comparer;
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| 41 |
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| 42 | foreach (var item in collection) {
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| 43 | if (Count == Capacity)
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| 44 | Grow();
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| 45 |
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| 46 | _heap[_tail++] = item;
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| 47 | }
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| 48 |
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| 49 | for (int i = Parent(_tail - 1); i >= 0; i--)
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| 50 | BubbleDown(i);
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| 51 | }
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| 52 | protected Heap(Heap<T> original) {
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| 53 | // clone;
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| 54 | this._capacity = original._capacity;
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| 55 | this._tail = original._tail;
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| 56 | this._heap = new T[original._heap.Length];
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| 57 | Array.Copy(original._heap, this._heap, this._heap.Length);
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| 58 | this.Comparer = original.Comparer;
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| 59 | }
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| 60 |
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| 61 | public void Add(T item) {
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| 62 | if (Count == Capacity)
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| 63 | Grow();
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| 64 |
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| 65 | _heap[_tail++] = item;
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| 66 | BubbleUp(_tail - 1);
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| 67 | }
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| 68 |
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| 69 | private void BubbleUp(int i) {
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| 70 | if (i == 0 || Dominates(_heap[Parent(i)], _heap[i]))
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| 71 | return; //correct domination (or root)
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| 72 |
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| 73 | Swap(i, Parent(i));
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| 74 | BubbleUp(Parent(i));
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| 75 | }
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| 76 |
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| 77 | public T GetMin() {
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| 78 | if (Count == 0) throw new InvalidOperationException("Heap is empty");
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| 79 | return _heap[0];
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| 80 | }
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| 81 |
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| 82 | public T ExtractDominating() {
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| 83 | if (Count == 0) throw new InvalidOperationException("Heap is empty");
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| 84 | T ret = _heap[0];
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| 85 | _tail--;
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| 86 | Swap(_tail, 0);
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| 87 | BubbleDown(0);
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| 88 | return ret;
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| 89 | }
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| 90 |
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| 91 | private void BubbleDown(int i) {
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| 92 | int dominatingNode = Dominating(i);
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| 93 | if (dominatingNode == i) return;
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| 94 | Swap(i, dominatingNode);
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| 95 | BubbleDown(dominatingNode);
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| 96 | }
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| 97 |
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| 98 | private int Dominating(int i) {
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| 99 | int dominatingNode = i;
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| 100 | dominatingNode = GetDominating(YoungChild(i), dominatingNode);
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| 101 | dominatingNode = GetDominating(OldChild(i), dominatingNode);
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| 102 |
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| 103 | return dominatingNode;
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| 104 | }
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| 105 |
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| 106 | private int GetDominating(int newNode, int dominatingNode) {
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| 107 | if (newNode < _tail && !Dominates(_heap[dominatingNode], _heap[newNode]))
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| 108 | return newNode;
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| 109 | else
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| 110 | return dominatingNode;
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| 111 | }
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| 112 |
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| 113 | private void Swap(int i, int j) {
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| 114 | T tmp = _heap[i];
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| 115 | _heap[i] = _heap[j];
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| 116 | _heap[j] = tmp;
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| 117 | }
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| 118 |
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| 119 | private static int Parent(int i) {
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| 120 | return (i + 1) / 2 - 1;
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| 121 | }
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| 122 |
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| 123 | private static int YoungChild(int i) {
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| 124 | return (i + 1) * 2 - 1;
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| 125 | }
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| 126 |
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| 127 | private static int OldChild(int i) {
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| 128 | return YoungChild(i) + 1;
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| 129 | }
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| 130 |
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| 131 | private void Grow() {
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| 132 | int newCapacity = _capacity * GrowFactor + MinGrow;
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| 133 | var newHeap = new T[newCapacity];
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| 134 | Array.Copy(_heap, newHeap, _capacity);
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| 135 | _heap = newHeap;
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| 136 | _capacity = newCapacity;
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| 137 | }
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| 138 |
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| 139 | public IEnumerator<T> GetEnumerator() {
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| 140 | return _heap.Take(Count).GetEnumerator();
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| 141 | }
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| 142 |
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| 143 | IEnumerator IEnumerable.GetEnumerator() {
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| 144 | return GetEnumerator();
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| 145 | }
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| 146 | }
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| 147 |
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| 148 | public class MaxHeap<T> : Heap<T> {
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| 149 | public MaxHeap()
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| 150 | : this(Comparer<T>.Default) {
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| 151 | }
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| 152 |
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| 153 | public MaxHeap(Comparer<T> comparer)
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| 154 | : base(comparer) {
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| 155 | }
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| 156 |
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| 157 | public MaxHeap(IEnumerable<T> collection, Comparer<T> comparer)
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| 158 | : base(collection, comparer) {
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| 159 | }
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| 160 |
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| 161 | public MaxHeap(IEnumerable<T> collection)
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| 162 | : base(collection) {
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| 163 | }
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| 164 | public MaxHeap(MaxHeap<T> original) : base(original) { }
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| 165 |
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| 166 | protected override bool Dominates(T x, T y) {
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| 167 | return Comparer.Compare(x, y) >= 0;
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| 168 | }
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| 169 | }
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| 170 |
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| 171 | public class MinHeap<T> : Heap<T> {
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| 172 | public MinHeap()
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| 173 | : this(Comparer<T>.Default) {
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| 174 | }
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| 175 |
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| 176 | public MinHeap(Comparer<T> comparer)
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| 177 | : base(comparer) {
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| 178 | }
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| 179 |
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| 180 | public MinHeap(IEnumerable<T> collection)
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| 181 | : base(collection) {
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| 182 | }
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| 183 |
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| 184 | public MinHeap(IEnumerable<T> collection, Comparer<T> comparer)
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| 185 | : base(collection, comparer) {
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| 186 | }
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| 187 | public MinHeap(MinHeap<T> original) : base(original) { }
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| 188 |
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| 189 | protected override bool Dominates(T x, T y) {
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| 190 | return Comparer.Compare(x, y) <= 0;
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| 191 | }
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| 192 | } |
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