| | 1 | | using System.Collections; |
| | 2 | | using System.Diagnostics.CodeAnalysis; |
| | 3 | | using MoreStructures.PriorityQueues.ArrayList; |
| | 4 | |
|
| | 5 | | namespace MoreStructures.PriorityQueues.BinaryHeap; |
| | 6 | |
|
| | 7 | | /// <summary> |
| | 8 | | /// An <see cref="IPriorityQueue{T}"/> implementation based on a Binary Max Heap of its items. On top of basic |
| | 9 | | /// operations it also supports <see cref="IPeekKthPriorityQueue{T}"/> and |
| | 10 | | /// <see cref="IMergeablePriorityQueue{T, TPQTarget}"/>. |
| | 11 | | /// </summary> |
| | 12 | | /// <typeparam name="T"><inheritdoc cref="IPriorityQueue{T}"/></typeparam> |
| | 13 | | /// <remarks> |
| | 14 | | /// <para id="advantages"> |
| | 15 | | /// ADVANTAGES AND DISADVANTAGES |
| | 16 | | /// <br/> |
| | 17 | | /// - The Binary Max Heap is used to store items with their priorities, in a way that the item with max priority is |
| | 18 | | /// immediately retrievable (making <see cref="Peek"/> a constant-time operation), and easily extractable (making |
| | 19 | | /// <see cref="Pop"/> a logarithmic-time operation). |
| | 20 | | /// <br/> |
| | 21 | | /// - This comes a cost of the <see cref="Push(T, int)"/> operation, which is O(1) in |
| | 22 | | /// <see cref="ArrayListPriorityQueue{T}"/> and becomes a logarithmic-time operation in this implementation. |
| | 23 | | /// <br/> |
| | 24 | | /// - So this implementation can be considered as a balanced compromise between insertion and extraction, which |
| | 25 | | /// complexifies the underlying data structure and loses some performance in insertion to obtain all-around |
| | 26 | | /// logarithmic performance. |
| | 27 | | /// <br/> |
| | 28 | | /// - Given the "exponentially better" runtime of logarithmic operations w.r.t. linear ones, such compromise makes |
| | 29 | | /// sense for most scenarios. |
| | 30 | | /// <br/> |
| | 31 | | /// - Merging two Binary Max Heap structures, however, still requires linear time. If merging performance is |
| | 32 | | /// critical, a more advanced tree-based implementation, such as |
| | 33 | | /// <see cref="BinomialHeap.BinomialHeapPriorityQueue{T}"/>, |
| | 34 | | /// <see cref="FibonacciHeap.FibonacciHeapPriorityQueue{T}"/> and their derivations, should be used instead. |
| | 35 | | /// </para> |
| | 36 | | /// <para id="heap-representation"> |
| | 37 | | /// BINARY MAX HEAP REPRESENTATION |
| | 38 | | /// <br/> |
| | 39 | | /// - The Binary Max Heap used for items and priorities is backed by a complete Binary Tree, represented as an |
| | 40 | | /// Array List of its items. |
| | 41 | | /// <br/> |
| | 42 | | /// - The root of the tree is always in position 0, its children in positions 1 and 2, grand-children in positions |
| | 43 | | /// 3, 4, 5 and 6 (where 3 and 4 are children of 1 and 5 and 6 are children of 2), etc. |
| | 44 | | /// <br/> |
| | 45 | | /// - This is the most space-efficient layout for a complete tree, which allows O(1) root access, parent-to-child |
| | 46 | | /// navigation and child-to-parent navigation, by performing simple indexing arithmetic. |
| | 47 | | /// <br/> |
| | 48 | | /// - The underlying Binary Tree is complete, hence balanced: it's height h is Math.Floor(log(n, 2)), where n is |
| | 49 | | /// the number of nodes in the tree. For example a complete Binary Tree of 3 nodes has necessarily height 1, |
| | 50 | | /// whereas one of 4 nodes has to have height 2. |
| | 51 | | /// <br/> |
| | 52 | | /// - While the Binary Tree is complete, it is non necessarily full, meaning that the last level may not be |
| | 53 | | /// entirely filled with leaves and the number of leaves at the last level may vary from 1 up to 2^(h + 1) - 1. |
| | 54 | | /// <br/> |
| | 55 | | /// - All modification operations (such as <see cref="Pop"/>) done on the Binary Max Heap ensure that the tree is |
| | 56 | | /// kept complete and balanced. |
| | 57 | | /// </para> |
| | 58 | | /// <para id="repetitions"> |
| | 59 | | /// REPEATED ITEMS AND PRIORITIES |
| | 60 | | /// <br/> |
| | 61 | | /// - Repeated items, as well as repeated priorities, are supported. |
| | 62 | | /// <br/> |
| | 63 | | /// - The implementation is <b>stable</b> both for priorities and items. |
| | 64 | | /// <br/> |
| | 65 | | /// - If two items I1 and I2 are pushed with the same priority P at times T1 and T2 with T1 < T2, when P becomes |
| | 66 | | /// the highest priority in the heap, I1 is popped out of the heap before I2 is. |
| | 67 | | /// <br/> |
| | 68 | | /// - That also applies to the case where I1 and I2 are equal by value and different by reference. |
| | 69 | | /// <br/> |
| | 70 | | /// - Stability is achieved by keeping a "push index", i.e. a <see cref="int"/> counter set to 0 in the constructor |
| | 71 | | /// and incremented every time a new item is introduced in the queue via a <see cref="Push(T, int)"/>. |
| | 72 | | /// <br/> |
| | 73 | | /// - The push index is included in the heap item record, together with the item of type |
| | 74 | | /// <typeparamref name="T"/> and its priority of type <see cref="int"/>. |
| | 75 | | /// <br/> |
| | 76 | | /// - This way two heap item records I1 and I2 with the same priority I1.Priority and I2.Priority, and potentially |
| | 77 | | /// the same or equal items I1.Item and I2.Item, will necessarily differ by push index, I1.PushTimestamp and |
| | 78 | | /// I2.PushTimestamp. |
| | 79 | | /// <br/> |
| | 80 | | /// - Therefore a <b>total strict order</b> can be imposed. |
| | 81 | | /// </para> |
| | 82 | | /// </remarks> |
| | 83 | | public class BinaryHeapPriorityQueue<T> |
| | 84 | | : IPeekKthPriorityQueue<T>, IMergeablePriorityQueue<T, BinaryHeapPriorityQueue<T>> |
| | 85 | | where T : notnull |
| | 86 | | { |
| | 87 | | /// <summary> |
| | 88 | | /// A non-negative, zero-based, monotonically strictly increasing counter, incremented at every insertion into this |
| | 89 | | /// data structure by a <see cref="Push(T, int)"/>. |
| | 90 | | /// </summary> |
| 40401 | 91 | | protected int CurrentPushTimestamp { get; set; } = 0; |
| | 92 | |
|
| | 93 | | /// <summary> |
| | 94 | | /// The wrapped <see cref="IList{T}"/> of <see cref="PrioritizedItem{T}"/> backing the binary max heap. |
| | 95 | | /// </summary> |
| 67631 | 96 | | protected BinaryHeapListWrapper<PrioritizedItem<T>> Items { get; } |
| | 97 | |
|
| | 98 | | /// <summary> |
| | 99 | | /// Builds an empty priority queue. |
| | 100 | | /// </summary> |
| | 101 | | /// <remarks> |
| | 102 | | /// The underlying data structure for priorities and items is initialized to an empty structure. |
| | 103 | | /// <br/> |
| | 104 | | /// Therefore, Time and Space Complexity is O(1). |
| | 105 | | /// </remarks> |
| 5577 | 106 | | public BinaryHeapPriorityQueue() |
| 5577 | 107 | | { |
| 5577 | 108 | | Items = |
| 5577 | 109 | | new(new List<PrioritizedItem<T>>(), Comparer<PrioritizedItem<T>>.Default, 0) |
| 5577 | 110 | | { |
| 5577 | 111 | | RaiseItemPushed = RaiseItemPushed, |
| 5577 | 112 | | RaiseItemPopping = RaiseItemPopping, |
| 5577 | 113 | | RaiseItemsSwapped = RaiseItemsSwapped, |
| 5577 | 114 | | }; |
| 5577 | 115 | | } |
| | 116 | |
|
| | 117 | | /// <summary> |
| | 118 | | /// Builds a new priority queue with the same items of the provided <paramref name="source"/>. |
| | 119 | | /// </summary> |
| | 120 | | /// <param name="source">The <see cref="BinaryHeapPriorityQueue{T}"/> instance to use as a source of data.</param> |
| | 121 | | /// <remarks> |
| | 122 | | /// The underlying data structure is shallow copied. |
| | 123 | | /// <br/> |
| | 124 | | /// Because it is made of immutable records, a shallow-copy is enough to ensure that its mutation in |
| | 125 | | /// <paramref name="source"/> won't affect the new priority queue or viceversa. |
| | 126 | | /// <br/> |
| | 127 | | /// Because the data structure contain O(n) items, Time and Space Complexity are O(n), where n is the number of |
| | 128 | | /// items in <paramref name="source"/>. |
| | 129 | | /// </remarks> |
| 252 | 130 | | protected BinaryHeapPriorityQueue(BinaryHeapPriorityQueue<T> source) |
| 252 | 131 | | { |
| 252 | 132 | | Items = |
| 252 | 133 | | new(source.Items) |
| 252 | 134 | | { |
| 252 | 135 | | RaiseItemPushed = RaiseItemPushed, |
| 252 | 136 | | RaiseItemPopping = RaiseItemPopping, |
| 252 | 137 | | RaiseItemsSwapped = RaiseItemsSwapped, |
| 252 | 138 | | }; |
| 252 | 139 | | } |
| | 140 | |
|
| | 141 | | #region Public API |
| | 142 | |
|
| | 143 | | /// <inheritdoc path="//*[not(self::remarks)]"/> |
| | 144 | | /// <remarks> |
| | 145 | | /// Checks the count of the underlying heap. |
| | 146 | | /// <br/> |
| | 147 | | /// The size of the heap may be smaller than the size of the underlying list, if there is buffer at the end. |
| | 148 | | /// <br/> |
| | 149 | | /// Time and Space Complexity are O(1). |
| | 150 | | /// </remarks> |
| 6856 | 151 | | public virtual int Count => Items.HeapCount; |
| | 152 | |
|
| | 153 | | /// <inheritdoc path="//*[not(self::remarks)]"/> |
| | 154 | | /// <remarks> |
| | 155 | | /// In order to return items in heap order (i.e. the max at each step), it first copies this priority queue into a |
| | 156 | | /// second temporary queue, which can be mutated without affecting the state of this queue. |
| | 157 | | /// <br/> |
| | 158 | | /// It then iterates over the copy, calling <see cref="Pop"/> until it becomes empty. |
| | 159 | | /// <br/> |
| | 160 | | /// Time Complexity is O(n * log(n)) (when fully enumerated), because a single <see cref="Pop"/> on an complete |
| | 161 | | /// binary heap takes logarithmic time, and there are n items to be extracted. |
| | 162 | | /// <br/> |
| | 163 | | /// Space Complexity is O(n), as a copy of this queue is required as auxiliary data structure to emit elements in |
| | 164 | | /// the right order of priority. |
| | 165 | | /// </remarks> |
| | 166 | | public virtual IEnumerator<T> GetEnumerator() |
| 252 | 167 | | { |
| 252 | 168 | | var copy = new BinaryHeapPriorityQueue<T>(this); |
| 5998 | 169 | | while (copy.Count > 0) |
| 5754 | 170 | | yield return copy.Pop().Item; |
| 244 | 171 | | } |
| | 172 | |
|
| | 173 | | /// <inheritdoc path="//*[not(self::remarks)]"/> |
| | 174 | | /// <remarks> |
| | 175 | | /// <inheritdoc cref="GetEnumerator"/> |
| | 176 | | /// </remarks> |
| 2 | 177 | | IEnumerator IEnumerable.GetEnumerator() => GetEnumerator(); |
| | 178 | |
|
| | 179 | | /// <inheritdoc path="//*[not(self::remarks)]"/> |
| | 180 | | /// <remarks> |
| | 181 | | /// Peeks the item with max priority from the root of the heap, if any. |
| | 182 | | /// <br/> |
| | 183 | | /// That is located at index 0 in the underlying list, and can be accessed in constant-time. |
| | 184 | | /// <br/> |
| | 185 | | /// Therefore, Time and Space Complexity are O(1). |
| | 186 | | /// </remarks> |
| 433 | 187 | | public virtual PrioritizedItem<T> Peek() => Items.Peek(); |
| | 188 | |
|
| | 189 | | /// <inheritdoc path="//*[not(self::remarks)]"/> |
| | 190 | | /// <remarks> |
| | 191 | | /// <para id="algorithm"> |
| | 192 | | /// ALGORITHM |
| | 193 | | /// <br/> |
| | 194 | | /// - Peeks the first item from the heap and stores to return it as result. |
| | 195 | | /// <br/> |
| | 196 | | /// - Takes the last item of the heap and moves to the root, in first position. |
| | 197 | | /// <br/> |
| | 198 | | /// - Restores heap constraints by recursively sifting down new root, as many time as needed. |
| | 199 | | /// </para> |
| | 200 | | /// <para id="complexity"> |
| | 201 | | /// COMPLEXITY |
| | 202 | | /// <br/> |
| | 203 | | /// - <see cref="Peek"/> and removal of item with max priority and last leaf of the heap are all constant-time |
| | 204 | | /// operations. |
| | 205 | | /// <br/> |
| | 206 | | /// - Since the heap is an complete binary tree, the heigh of the three is O(log(n)). |
| | 207 | | /// <br/> |
| | 208 | | /// - So the number of "sift down" operations is logarithmic w.r.t. the input. |
| | 209 | | /// <br/> |
| | 210 | | /// - Therefore, Time Complexity is O(log(n)) and Space Complexity is O(1), since modifications are all done |
| | 211 | | /// in-place in underlying data structures. |
| | 212 | | /// </para> |
| | 213 | | /// </remarks> |
| 8425 | 214 | | public virtual PrioritizedItem<T> Pop() => Items.Pop(); |
| | 215 | |
|
| | 216 | | /// <inheritdoc path="//*[not(self::remarks)]"/> |
| | 217 | | /// <remarks> |
| | 218 | | /// Negative priorities are supported. |
| | 219 | | /// <para id="algorithm"> |
| | 220 | | /// ALGORITHM |
| | 221 | | /// <br/> |
| | 222 | | /// - Adds a new leaf to the heap, carrying priority, item and unique push index. |
| | 223 | | /// <br/> |
| | 224 | | /// - Restores heap constraints by recursively sifting up new leaf, as many time as needed. |
| | 225 | | /// </para> |
| | 226 | | /// <para id="complexity"> |
| | 227 | | /// COMPLEXITY |
| | 228 | | /// <br/> |
| | 229 | | /// - Adding a new item with given priority and a leaf to the heap are constant-time operations. |
| | 230 | | /// <br/> |
| | 231 | | /// - Since the heap is an complete binary tree, the heigh of the three is O(log(n)). |
| | 232 | | /// <br/> |
| | 233 | | /// - So the number of "sift up" operations is logarithmic w.r.t. the input. |
| | 234 | | /// <br/> |
| | 235 | | /// - Therefore, Time Complexity is O(log(n)) and Space Complexity is O(1), since modifications are all done |
| | 236 | | /// in-place in underlying data structure. |
| | 237 | | /// </para> |
| | 238 | | /// </remarks> |
| 13341 | 239 | | public virtual void Push(T item, int priority) => Items.Push(new(item, priority, CurrentPushTimestamp++)); |
| | 240 | |
|
| | 241 | | /// <inheritdoc path="//*[not(self::remarks)]"/> |
| | 242 | | /// <remarks> |
| | 243 | | /// <para id="algorithm"> |
| | 244 | | /// ALGORITHM |
| | 245 | | /// <br/> |
| | 246 | | /// - If <paramref name="k"/> is negative, an <see cref="ArgumentException"/> is returned. |
| | 247 | | /// <br/> |
| | 248 | | /// - If <paramref name="k"/> is non-smaller than the <see cref="Count"/>, <see langword="null"/> is returned. |
| | 249 | | /// <br/> |
| | 250 | | /// - If <paramref name="k"/> is 0, <see cref="Peek"/> is returned. |
| | 251 | | /// <br/> |
| | 252 | | /// - Otherwise, the main algorithm loop is performed, at most <paramref name="k"/> times. |
| | 253 | | /// <br/> |
| | 254 | | /// - A dedicated <see cref="BinaryHeapPriorityQueue{T}"/> C of <see cref="int"/> values is instantiated. |
| | 255 | | /// <br/> |
| | 256 | | /// - The values of C are the indexes of the underlying list of this priority queue, and identify candidates |
| | 257 | | /// for the <paramref name="k"/>-th largest item. |
| | 258 | | /// <br/> |
| | 259 | | /// - Such candidates are sorted in C by priority and push timestamps, exactly in the same way they are |
| | 260 | | /// sorted in this priority queue. |
| | 261 | | /// <br/> |
| | 262 | | /// - At the beginning only the root of the priority queue (i.e. index 0) is pushed to C. |
| | 263 | | /// <br/> |
| | 264 | | /// - At each iteration the max of C is popped from C and its left and right children (if any) are pushed into |
| | 265 | | /// C. |
| | 266 | | /// <br/> |
| | 267 | | /// - After <paramref name="k"/> iterations, the <see cref="Peek"/> of C gives the <paramref name="k"/>-th |
| | 268 | | /// largest item. |
| | 269 | | /// <br/> |
| | 270 | | /// - Notice that C cannot run short of candidates (due to lack of children), because of the preconditions |
| | 271 | | /// on <paramref name="k"/>. |
| | 272 | | /// </para> |
| | 273 | | /// <para id="complexity"> |
| | 274 | | /// COMPLEXITY |
| | 275 | | /// <br/> |
| | 276 | | /// - Checks on the value of <paramref name="k"/> w.r.t. the size of this priority queue and direct access to |
| | 277 | | /// the underlying list, to return the final result once the index has been found, are both done in constant |
| | 278 | | /// time. |
| | 279 | | /// <br/> |
| | 280 | | /// - Candidates queue instantiation and 1st push into it are also constant time operations. |
| | 281 | | /// <br/> |
| | 282 | | /// - The main loop consist of k iterations. |
| | 283 | | /// <br/> |
| | 284 | | /// - At each iteration 1 item is popped and 2 are pushed, so the candidates queue grows of 1 item per cycle. |
| | 285 | | /// <br/> |
| | 286 | | /// - Each <see cref="Pop"/> and <see cref="Push(T, int)"/> operation on the candidates queue has logarithmic |
| | 287 | | /// run, since they are done on a <see cref="BinaryHeapPriorityQueue{T}"/> instance. |
| | 288 | | /// <br/> |
| | 289 | | /// - Therefore, Time Complexity is O(k * log(k)) and Space Complexity is O(k). |
| | 290 | | /// </para> |
| | 291 | | /// </remarks> |
| 26 | 292 | | public virtual PrioritizedItem<T>? PeekKth(int k) => Items.PeekKth(k) is (var result, true) ? result : null; |
| | 293 | |
|
| | 294 | | /// <inheritdoc path="//*[not(self::remarks)]"/> |
| | 295 | | /// <remarks> |
| | 296 | | /// <para id="algorithm"> |
| | 297 | | /// ALGORITHM |
| | 298 | | /// <br/> |
| | 299 | | /// - Pushing all items in the <paramref name="targetPriorityQueue"/> via <see cref="Push(T, int)"/>, would |
| | 300 | | /// result in O(m * log(m)) Time Complexity, where m is the number of items in the |
| | 301 | | /// <paramref name="targetPriorityQueue"/>. |
| | 302 | | /// <br/> |
| | 303 | | /// - Instead, each of the m items from the <paramref name="targetPriorityQueue"/> is added to the underlying |
| | 304 | | /// array list of this queue, at the end. |
| | 305 | | /// <br/> |
| | 306 | | /// - Then, the content of <paramref name="targetPriorityQueue"/> is cleared, to respect the contract defined |
| | 307 | | /// by <see cref="IMergeablePriorityQueue{T, TPQTarget}"/>. |
| | 308 | | /// <br/> |
| | 309 | | /// - Finally, the heap property is restored globally for all items in the underlying array list, by sifting |
| | 310 | | /// down all items in the first half of the list, proceeding backwards from the middle of the list to its |
| | 311 | | /// first item. |
| | 312 | | /// <br/> |
| | 313 | | /// - Such global sift down is required for the first half of the items only, because the second half only |
| | 314 | | /// contains leaves of the tree, for which a sift down would do nothing (i.e. the heap property is already |
| | 315 | | /// satisfied). |
| | 316 | | /// </para> |
| | 317 | | /// <para id="complexity"> |
| | 318 | | /// COMPLEXITY |
| | 319 | | /// <br/> |
| | 320 | | /// - Appending m items has a linear cost over m. |
| | 321 | | /// <br/> |
| | 322 | | /// - Clearing the target only takes constant time. |
| | 323 | | /// <br/> |
| | 324 | | /// - Restoring the heap property globally would seem to take n / 2 * log(n), where n is the total number of |
| | 325 | | /// items in this queue, after the merge: the number of items to sift down plus the cost of sifting down the |
| | 326 | | /// tree. That would give O(n * log(n)) complexity: not a real improvement over the naive approach of pushing |
| | 327 | | /// n items. |
| | 328 | | /// <br/> |
| | 329 | | /// - However, the length of the path to sift down is not as big as the entire height of the tree. Instead, the |
| | 330 | | /// closer the starting node is to the leave, the smaller it becomes: leaves have sift down paths of length |
| | 331 | | /// 0, their parent of length 1, etc., up to the root, which has sift down path of length equal to the height |
| | 332 | | /// of the tree. |
| | 333 | | /// <br/> |
| | 334 | | /// - A key observation is that in a complete and full tree there are more leaves than all nodes in other |
| | 335 | | /// levels combined, and that applies to all levels w.r.t. all smaller levels. |
| | 336 | | /// <br/> |
| | 337 | | /// - So, sift down will cost less for way more nodes, resulting in overall O(n) Time Complexity. |
| | 338 | | /// <br/> |
| | 339 | | /// - Space Complexity is O(m), since m items are added to the list storing the items of this queue. |
| | 340 | | /// </para> |
| | 341 | | /// </remarks> |
| | 342 | | public virtual void MergeFrom(BinaryHeapPriorityQueue<T> targetPriorityQueue) |
| 236 | 343 | | { |
| 5968 | 344 | | foreach (var prioritizedItem in targetPriorityQueue.Items) |
| 2630 | 345 | | { |
| 2630 | 346 | | Items.Push(new(prioritizedItem.Item, prioritizedItem.Priority, CurrentPushTimestamp), false); |
| 2630 | 347 | | CurrentPushTimestamp++; |
| 2630 | 348 | | } |
| | 349 | |
|
| 236 | 350 | | targetPriorityQueue.Clear(); |
| | 351 | |
|
| 236 | 352 | | Items.RestoreHeapProperty(); |
| 236 | 353 | | } |
| | 354 | |
|
| | 355 | | /// <inheritdoc path="//*[not(self::remarks)]"/> |
| | 356 | | /// <remarks> |
| | 357 | | /// Just clears the underlying array list. |
| | 358 | | /// <br/> |
| | 359 | | /// The internal push timestamp counter is not reset, nor the era. Therefore, new pushes after the clear will |
| | 360 | | /// receive push timestamps strictly higher than the ones assigned to the items in the queue before the clear. |
| | 361 | | /// <br/> |
| | 362 | | /// Time and Space Complexity are O(1). |
| | 363 | | /// </remarks> |
| 345 | 364 | | public virtual void Clear() => Items.Clear(); |
| | 365 | |
|
| | 366 | | #endregion |
| | 367 | |
|
| | 368 | | #region Hooks |
| | 369 | |
|
| | 370 | | /// <summary> |
| | 371 | | /// Invoked just after an item has been pushed into <see cref="Items"/>. |
| | 372 | | /// </summary> |
| | 373 | | /// <param name="indexPushed"> |
| | 374 | | /// The index of the item being pushed. |
| | 375 | | /// <br/> |
| | 376 | | /// When the heap is at the beginning of the list (which is the layout used by this queue), it is equal to |
| | 377 | | /// Count - 1 if the underlying list is fully utilized, and it's smaller than that otherwise (there is buffer at |
| | 378 | | /// the end of the list, after the last item of the heap). |
| | 379 | | /// </param> |
| 21008 | 380 | | protected virtual void RaiseItemPushed(int indexPushed) { } |
| | 381 | |
|
| | 382 | | /// <summary> |
| | 383 | | /// Invoked just before an item is removed from <see cref="Items"/>. |
| | 384 | | /// </summary> |
| | 385 | | /// <param name="indexPopped"> |
| | 386 | | /// The index of the item being popped. |
| | 387 | | /// <br/> |
| | 388 | | /// When the heap is at the beginning of the list (which is the layout used by this queue), it is equal to 0. |
| | 389 | | /// </param> |
| | 390 | | /// <param name="indexInBufferArea"> |
| | 391 | | /// The index of the item of the last leaf, which is going to be swapped with the root during pop. |
| | 392 | | /// </param> |
| 13826 | 393 | | protected virtual void RaiseItemPopping(int indexPopped, int indexInBufferArea) { } |
| | 394 | |
|
| | 395 | | /// <summary> |
| | 396 | | /// Invoked just after two items have been swapped of position in <see cref="Items"/>. |
| | 397 | | /// </summary> |
| | 398 | | /// <param name="index1">The index of the first item swapped.</param> |
| | 399 | | /// <param name="index2">The index of the second item swapped.</param> |
| 95492 | 400 | | protected virtual void RaiseItemsSwapped(int index1, int index2) { } |
| | 401 | |
|
| | 402 | | #endregion |
| | 403 | | } |