| | | 1 | | namespace MoreStructures.RecImmTrees.Visitor; |
| | | 2 | | |
| | | 3 | | /// <inheritdoc cref="DepthFirstTraversal{TEdge, TNode}" path="//*[not(self::summary or self::remarks)]"/> |
| | | 4 | | /// <summary> |
| | | 5 | | /// A lazy, fully-recursive, depth-first <see cref="IVisitStrategy{TNode, TVisitContext}"/> implementation, i.e. a |
| | | 6 | | /// traversing strategy which goes in depth as far as possible along each path of the tree, only backtracking when a |
| | | 7 | | /// leaf is reached. |
| | | 8 | | /// </summary> |
| | | 9 | | /// <remarks> |
| | | 10 | | /// <inheritdoc cref="DepthFirstTraversal{TEdge, TNode}" path="/remarks"/> |
| | | 11 | | /// <para id="advantages"> |
| | | 12 | | /// ADVANTAGES AND DISADVANTAGES |
| | | 13 | | /// <br/> |
| | | 14 | | /// Implemented fully recursively, so limited by stack depth and usable with tree of a "reasonable" height. |
| | | 15 | | /// </para> |
| | | 16 | | /// </remarks> |
| | | 17 | | public class FullyRecursiveDepthFirstTraversal<TEdge, TNode> |
| | | 18 | | : DepthFirstTraversal<TEdge, TNode> |
| | | 19 | | where TEdge : IRecImmDictIndexedTreeEdge<TEdge, TNode> |
| | | 20 | | where TNode : IRecImmDictIndexedTreeNode<TEdge, TNode> |
| | | 21 | | { |
| | | 22 | | /// <inheritdoc |
| | | 23 | | /// cref="TreeTraversal{TEdge, TNode}.Visit(TNode)" |
| | | 24 | | /// path="//*[not(self::summary or self::remarks)]"/> |
| | | 25 | | /// <summary> |
| | | 26 | | /// <b>Lazily and recursively</b> visits the structure of the provided<paramref name= "node" />, returning the |
| | | 27 | | /// sequence of <see cref="IRecImmDictIndexedTreeNode{TEdge, TNode}"/> of the structure, in depth-first order. |
| | | 28 | | /// </summary> |
| | | 29 | | /// <remarks> |
| | | 30 | | /// <inheritdoc cref="FullyRecursiveDepthFirstTraversal{TEdge, TNode}" path="/remarks"/> |
| | | 31 | | /// <para id = "algo" > |
| | | 32 | | /// ALGORITHM |
| | | 33 | | /// <br/> |
| | | 34 | | /// - The algorithm visits all nodes in structure in natural recursion/depth-first order, yielding to the |
| | | 35 | | /// output sequence, so that the client code implementing the visitor can lazily process the nodes. |
| | | 36 | | /// </para> |
| | | 37 | | /// <para id="complexity"> |
| | | 38 | | /// COMPLEXITY |
| | | 39 | | /// <br/> |
| | | 40 | | /// - Excluding visitor, constant time work is done for each of the n nodes of the tree (such as construction |
| | | 41 | | /// of the input record for the visitor). |
| | | 42 | | /// <br/> |
| | | 43 | | /// - Iteration-cost is constant w.r.t. n. <see cref="TreeTraversal{TEdge, TNode}.ChildrenSorter"/> cost |
| | | 44 | | /// depends on the actual algorithm used. |
| | | 45 | | /// <br/> |
| | | 46 | | /// - So Time Complexity is dominated by <see cref="TreeTraversal{TEdge, TNode}.ChildrenSorter"/> and visitor. |
| | | 47 | | /// <br/> |
| | | 48 | | /// In conclusion: |
| | | 49 | | /// <br/> |
| | | 50 | | /// - Time Complexity is O(n * Ts), where Ts is the amortized time cost of |
| | | 51 | | /// <see cref="TreeTraversal{TEdge, TNode}.ChildrenSorter"/> per node. Taking into account the visit of |
| | | 52 | | /// each emitted node, Time Complexity is O(n * (Ts + Tv)), where Tv is the time cost of the visitor per |
| | | 53 | | /// node. |
| | | 54 | | /// <br/> |
| | | 55 | | /// - Space Complexity is O(n). Taking into account the visit of each emitted node, Space Complexity is |
| | | 56 | | /// O(n * Sv), where Sv is the space cost of visitor per node. |
| | | 57 | | /// </para> |
| | | 58 | | /// </remarks> |
| | | 59 | | public override IEnumerable<TreeTraversalVisit<TEdge, TNode>> Visit(TNode node) => |
| | 30 | 60 | | Visit(new(node, default, default, 0)); |
| | | 61 | | |
| | | 62 | | private IEnumerable<TreeTraversalVisit<TEdge, TNode>> Visit(TreeTraversalVisit<TEdge, TNode> visit) |
| | 829 | 63 | | { |
| | 829 | 64 | | var (node, _, _, level) = visit; |
| | | 65 | | |
| | 829 | 66 | | switch (TraversalOrder) |
| | | 67 | | { |
| | | 68 | | case TreeTraversalOrder.ParentFirst: |
| | 296 | 69 | | yield return visit; |
| | 1458 | 70 | | foreach (var child in ChildrenSorter(visit)) |
| | 21391 | 71 | | foreach (var childVisit in Visit(new(child.Value, node, child.Key, level + 1))) |
| | 10268 | 72 | | yield return childVisit; |
| | | 73 | | |
| | 296 | 74 | | break; |
| | | 75 | | |
| | | 76 | | case TreeTraversalOrder.ChildrenFirst: |
| | 2593 | 77 | | foreach (var child in ChildrenSorter(visit)) |
| | 5338 | 78 | | foreach (var childVisit in Visit(new(child.Value, node, child.Key, level + 1))) |
| | 1919 | 79 | | yield return childVisit; |
| | 531 | 80 | | yield return visit; |
| | | 81 | | |
| | 531 | 82 | | break; |
| | | 83 | | |
| | | 84 | | default: |
| | 2 | 85 | | throw new NotSupportedException($"{nameof(TreeTraversalOrder)} {TraversalOrder} is not supported"); |
| | | 86 | | } |
| | 827 | 87 | | } |
| | | 88 | | } |