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POPerformance of an AVL Tree in C#
 

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  1. POPerformance of an AVL Tree in C#
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    <p>I have implemented an AVL tree in C# whose insertion matrix is as follows</p> <pre><code>Number of Elements Time taken to insert (sec) ------------------------------------------------------ 10 0.067 100 0.073 200 0.112 500 0.388 900 1.205 1000 1.466 5000 44.314 10000 195.435 </code></pre> <p>Now my question is, is it a good performance for an AVL tree or do I have to re-consider changing the algorithm or refactoring the code?</p> <hr> <p>Edit: The elements are integer starting from 0 to #of elements Test code is as follows</p> <pre><code> [Test] public void InsertionTest() { AVLTree&lt;int&gt; _tree = new AVLTree&lt;int&gt;(); _stopWatch.Start(); for (int i = 0; i &lt; 5000; i++) { _tree.Add(i); } _stopWatch.Stop(); Console.WriteLine("Time taken = " + _stopWatch.Elapsed); } </code></pre> <hr> <p>Edit: Implementation code</p> <p>BinarySearchTree</p> <pre><code>[Serializable] public class BinarySearchTree&lt;T&gt; : ICollection&lt;T&gt; { private readonly Comparer&lt;T&gt; _comparer = Comparer&lt;T&gt;.Default; public BinarySearchTree() { } public BinarySearchTree(IEnumerable&lt;T&gt; collection) { AddRange(collection.ToArray()); } public BinarySearchTree(Comparer&lt;T&gt; comparer) { _comparer = comparer; } public BinaryTreeNode&lt;T&gt; Root { get; protected set; } #region ICollection&lt;T&gt; Members /// &lt;summary&gt; /// Adds an item to the &lt;see cref = "T:System.Collections.Generic.ICollection`1" /&gt;. /// &lt;/summary&gt; /// &lt;param name = "value"&gt;The object to add to the &lt;see cref = "T:System.Collections.Generic.ICollection`1" /&gt;. /// &lt;/param&gt; /// &lt;exception cref = "T:System.NotSupportedException"&gt;The &lt;see cref = "T:System.Collections.Generic.ICollection`1" /&gt; is read-only. /// &lt;/exception&gt; public virtual void Add(T value) { var n = new BinaryTreeNode&lt;T&gt;(value); int result; BinaryTreeNode&lt;T&gt; current = Root, parent = null; while (current != null) { result = _comparer.Compare(current.Value, value); if (result == 0) { parent = current; current = current.Left; } if (result &gt; 0) { parent = current; current = current.Left; } else if (result &lt; 0) { parent = current; current = current.Right; } } Count++; if (parent == null) Root = n; else { result = _comparer.Compare(parent.Value, value); if (result &gt; 0) parent.Left = n; else parent.Right = n; } } /// &lt;summary&gt; /// Removes all items from the &lt;see cref = "T:System.Collections.Generic.ICollection`1" /&gt;. /// &lt;/summary&gt; /// &lt;exception cref = "T:System.NotSupportedException"&gt;The &lt;see cref = "T:System.Collections.Generic.ICollection`1" /&gt; is read-only. /// &lt;/exception&gt; public void Clear() { Root = null; Count = 0; } /// &lt;summary&gt; /// Determines whether the &lt;see cref = "T:System.Collections.Generic.ICollection`1" /&gt; contains a specific value. /// &lt;/summary&gt; /// &lt;returns&gt; /// true if &lt;paramref name = "item" /&gt; is found in the &lt;see cref = "T:System.Collections.Generic.ICollection`1" /&gt;; otherwise, false. /// &lt;/returns&gt; /// &lt;param name = "item"&gt;The object to locate in the &lt;see cref = "T:System.Collections.Generic.ICollection`1" /&gt;. /// &lt;/param&gt; public virtual bool Contains(T item) { BinaryTreeNode&lt;T&gt; current = Root; while (current != null) { int result = _comparer.Compare(current.Value, item); if (result == 0) return true; if (result &gt; 0) current = current.Left; else if (result &lt; 0) current = current.Right; } return false; } public void CopyTo(T[] array, int index) { CopyTo(array, index, BinaryTreeTraversalType.InOrder); } /// &lt;summary&gt; /// Removes the first occurrence of a specific object from the &lt;see cref = "T:System.Collections.Generic.ICollection`1" /&gt;. /// &lt;/summary&gt; /// &lt;returns&gt; /// true if &lt;paramref name = "item" /&gt; was successfully removed from the &lt;see cref = "T:System.Collections.Generic.ICollection`1" /&gt;; otherwise, false. This method also returns false if &lt;paramref name = "item" /&gt; is not found in the original &lt;see cref = "T:System.Collections.Generic.ICollection`1" /&gt;. /// &lt;/returns&gt; /// &lt;param name = "item"&gt;The object to remove from the &lt;see cref = "T:System.Collections.Generic.ICollection`1" /&gt;. /// &lt;/param&gt; /// &lt;exception cref = "T:System.NotSupportedException"&gt;The &lt;see cref = "T:System.Collections.Generic.ICollection`1" /&gt; is read-only. /// &lt;/exception&gt; public virtual bool Remove(T item) { if (Root == null) return false; BinaryTreeNode&lt;T&gt; current = Root, parent = null; int result = _comparer.Compare(current.Value, item); while (result != 0) { if (result &gt; 0) { parent = current; current = current.Left; } else if (result &lt; 0) { parent = current; current = current.Right; } if (current == null) return false; result = _comparer.Compare(current.Value, item); } Count--; // We now need to "rethread" the tree // CASE 1: If current has no right child, then current's left child becomes // the node pointed to by the parent if (current.Right == null) { if (parent == null) Root = current.Left; else { result = _comparer.Compare(parent.Value, current.Value); if (result &gt; 0) parent.Left = current.Left; else if (result &lt; 0) parent.Right = current.Left; } // CASE 2: If current's right child has no left child, then current's right child // replaces current in the tree } else if (current.Right.Left == null) { current.Right.Left = current.Left; if (parent == null) Root = current.Right; else { result = _comparer.Compare(parent.Value, current.Value); if (result &gt; 0) parent.Left = current.Right; else if (result &lt; 0) parent.Right = current.Right; } // CASE 3: If current's right child has a left child, replace current with current's // right child's left-most descendent } else { BinaryTreeNode&lt;T&gt; leftmost = current.Right.Left, lmParent = current.Right; while (leftmost.Left != null) { lmParent = leftmost; leftmost = leftmost.Left; } lmParent.Left = leftmost.Right; leftmost.Left = current.Left; leftmost.Right = current.Right; if (parent == null) Root = leftmost; else { result = _comparer.Compare(parent.Value, current.Value); if (result &gt; 0) parent.Left = leftmost; else if (result &lt; 0) parent.Right = leftmost; } } current.Left = current.Right = null; return true; } /// &lt;summary&gt; /// Gets the number of elements contained in the &lt;see cref = "T:System.Collections.Generic.ICollection`1" /&gt;. /// &lt;/summary&gt; /// &lt;returns&gt; /// The number of elements contained in the &lt;see cref = "T:System.Collections.Generic.ICollection`1" /&gt;. /// &lt;/returns&gt; public int Count { get; private set; } /// &lt;summary&gt; /// Gets a value indicating whether the &lt;see cref = "T:System.Collections.Generic.ICollection`1" /&gt; is read-only. /// &lt;/summary&gt; /// &lt;returns&gt; /// true if the &lt;see cref = "T:System.Collections.Generic.ICollection`1" /&gt; is read-only; otherwise, false. /// &lt;/returns&gt; public bool IsReadOnly { get { return false; } } #endregion public void AddRange(IEnumerable&lt;T&gt; items) { foreach (var item in items) { Add(item); } } public void CopyTo(T[] array, int index, BinaryTreeTraversalType traversalType) { Root.ToEnumerable(traversalType).Select(x =&gt; x.Value).ToArray().CopyTo(array, index); } public BinaryTreeNode&lt;T&gt; Find(T value) { BinaryTreeNode&lt;T&gt; current = Root; while (current != null) { int result = _comparer.Compare(current.Value, value); if (result == 0) return current; if (result &gt; 0) current = current.Left; else if (result &lt; 0) current = current.Right; } return null; } #region Implementation of IEnumerable /// &lt;summary&gt; /// Returns an enumerator that iterates through the collection. /// &lt;/summary&gt; /// &lt;returns&gt; /// A &lt;see cref = "T:System.Collections.Generic.IEnumerator`1" /&gt; that can be used to iterate through the collection. /// &lt;/returns&gt; /// &lt;filterpriority&gt;1&lt;/filterpriority&gt; public IEnumerator&lt;T&gt; GetEnumerator() { return Root.ToEnumerable(BinaryTreeTraversalType.InOrder).Select(x =&gt; x.Value).GetEnumerator(); } /// &lt;summary&gt; /// Returns an enumerator that iterates through a collection. /// &lt;/summary&gt; /// &lt;returns&gt; /// An &lt;see cref = "T:System.Collections.IEnumerator" /&gt; object that can be used to iterate through the collection. /// &lt;/returns&gt; /// &lt;filterpriority&gt;2&lt;/filterpriority&gt; IEnumerator IEnumerable.GetEnumerator() { return GetEnumerator(); } #endregion } </code></pre> <hr> <h2>AVLTree</h2> <pre><code>public class AVLTree&lt;T&gt; : BinarySearchTree&lt;T&gt; { public AVLTree() { } public AVLTree(IEnumerable&lt;T&gt; collection) : base(collection) { } public AVLTree(Comparer&lt;T&gt; comparer) : base(comparer) { } public override void Add(T value) { base.Add(value); var node = Find(value); AbstractNode&lt;T&gt; parentNode = node.Parent; while (parentNode != null) { int balance = GetBalance(parentNode as BinaryTreeNode&lt;T&gt;); if (Math.Abs(balance) == 2) { BalanceAt(parentNode as BinaryTreeNode&lt;T&gt;, balance); } parentNode = parentNode.Parent; } } public override bool Remove(T item) { if (Root == null) return false; BinaryTreeNode&lt;T&gt; valueNode = Find(item); AbstractNode&lt;T&gt; parentNode = valueNode.Parent; bool removed = base.Remove(item); if (!removed) return false; while (parentNode != null) { int balance = GetBalance(parentNode as BinaryTreeNode&lt;T&gt;); if (Math.Abs(balance) == 1) break; if (Math.Abs(balance) == 2) { BalanceAt(parentNode as BinaryTreeNode&lt;T&gt;, balance); } parentNode = parentNode.Parent; } return true; } /// &lt;summary&gt; /// Balances an AVL Tree node /// &lt;/summary&gt; protected virtual void BalanceAt(BinaryTreeNode&lt;T&gt; node, int balance) { if (balance == 2) { int rightBalance = GetBalance(node.Right); if (rightBalance == 1 || rightBalance == 0) { RotateLeft(node); } else if (rightBalance == -1) { RotateRight(node.Right); RotateLeft(node); } } else if (balance == -2) { int leftBalance = GetBalance(node.Left); if (leftBalance == 1) { RotateLeft(node.Left); RotateRight(node); } else if (leftBalance == -1 || leftBalance == 0) { RotateRight(node); } } } /// &lt;summary&gt; /// Determines the balance of a given node /// &lt;/summary&gt; protected virtual int GetBalance(BinaryTreeNode&lt;T&gt; node) { if(node != null) { IEnumerable&lt;BinaryTreeNode&lt;T&gt;&gt; leftSubtree = null, righSubtree = null; if (node.Left != null) leftSubtree = node.Left.ToEnumerable(BinaryTreeTraversalType.InOrder); if (node.Right != null) righSubtree = node.Right.ToEnumerable(BinaryTreeTraversalType.InOrder); // ReSharper disable AssignNullToNotNullAttribute var leftHeight = leftSubtree.IsNullOrEmpty() ? 0 : leftSubtree.Max(x =&gt; x.Depth) - node.Depth; var righHeight = righSubtree.IsNullOrEmpty() ? 0 : righSubtree.Max(x =&gt; x.Depth) - node.Depth; // ReSharper restore AssignNullToNotNullAttribute return righHeight - leftHeight; } return 0; } /// &lt;summary&gt; /// Rotates a node to the left within an AVL Tree /// &lt;/summary&gt; protected virtual void RotateLeft(BinaryTreeNode&lt;T&gt; node) { if (node == null) return; BinaryTreeNode&lt;T&gt; pivot = node.Right; if (pivot == null) return; var rootParent = node.Parent as BinaryTreeNode&lt;T&gt;; bool isLeftChild = (rootParent != null) &amp;&amp; rootParent.Left == node; bool makeTreeRoot = node == Root; node.Right = pivot.Left; pivot.Left = node; node.Parent = pivot; pivot.Parent = rootParent; if (node.Right != null) node.Right.Parent = node; if (makeTreeRoot) Root = pivot; if (isLeftChild) rootParent.Left = pivot; else if (rootParent != null) rootParent.Right = pivot; } /// &lt;summary&gt; /// Rotates a node to the right within an AVL Tree /// &lt;/summary&gt; protected virtual void RotateRight(BinaryTreeNode&lt;T&gt; node) { if (node == null) return; BinaryTreeNode&lt;T&gt; pivot = node.Left; if (pivot == null) return; var rootParent = node.Parent as BinaryTreeNode&lt;T&gt;; bool isLeftChild = (rootParent != null) &amp;&amp; rootParent.Left == node; bool makeTreeRoot = Root == node; node.Left = pivot.Right; pivot.Right = node; node.Parent = pivot; pivot.Parent = rootParent; if (node.Left != null) node.Left.Parent = node; if (makeTreeRoot) Root = pivot; if (isLeftChild) rootParent.Left = pivot; else if (rootParent != null) rootParent.Right = pivot; } } </code></pre>
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    1. USAnindya Chatterjee
    1. USAnindya Chatterjee
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      1. VTUpMod
    1. CO@downvoter plz mention the reason for down voting it
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      1. POPerformance of an AVL Tree in C#
      1. USAnindya Chatterjee
    2. COCould you show your AVL implementation and benchmarking code? If your tree code is too large, paste it into pastebin.com instead.
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      1. POPerformance of an AVL Tree in C#
      1. USJuliet
    3. COIf you repeat the 5.000 and 10.000 runs, are the results the same?
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      1. POPerformance of an AVL Tree in C#
      1. USHenk Holterman
 

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