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9991916
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0
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2012-04-03T11:01:07.363
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2012-04-03T11:23:01.893
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2012-04-03T11:23:01.893
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<p>This is my own re-implementation of Topological sorting, the idea is based on <a href="http://tawani.blogspot.com/2009/02/topological-sorting-and-cyclic.html" rel="noreferrer">http://tawani.blogspot.com/2009/02/topological-sorting-and-cyclic.html</a> (The ported Java source code consumes too much memory, checking 50k objects costs 50k*50k*4 = 10GB which is unacceptable. In addition, it still has Java coding convention some places)</p> <pre><code>using System.Collections.Generic; using System.Diagnostics; namespace Modules { /// <summary> /// Provides fast-algorithm and low-memory usage to sort objects based on their dependencies. /// </summary> /// <remarks> /// Definition: http://en.wikipedia.org/wiki/Topological_sorting /// Source code credited to: http://tawani.blogspot.com/2009/02/topological-sorting-and-cyclic.html /// Original Java source code: http://www.java2s.com/Code/Java/Collections-Data-Structure/Topologicalsorting.htm /// </remarks> /// <author>ThangTran</author> /// <history> /// 2012.03.21 - ThangTran: rewritten based on <see cref="TopologicalSorter"/>. /// </history> public class DependencySorter<T> { //************************************************** // // Private members // //************************************************** #region Private members /// <summary> /// Gets the dependency matrix used by this instance. /// </summary> private readonly Dictionary<T, Dictionary<T, object>> _matrix = new Dictionary<T, Dictionary<T, object>>(); #endregion //************************************************** // // Public methods // //************************************************** #region Public methods /// <summary> /// Adds a list of objects that will be sorted. /// </summary> public void AddObjects(params T[] objects) { // --- Begin parameters checking code ----------------------------- Debug.Assert(objects != null); Debug.Assert(objects.Length > 0); // --- End parameters checking code ------------------------------- // add to matrix foreach (T obj in objects) { // add to dictionary _matrix.Add(obj, new Dictionary<T, object>()); } } /// <summary> /// Sets dependencies of given object. /// This means <paramref name="obj"/> depends on these <paramref name="dependsOnObjects"/> to run. /// Please make sure objects given in the <paramref name="obj"/> and <paramref name="dependsOnObjects"/> are added first. /// </summary> public void SetDependencies(T obj, params T[] dependsOnObjects) { // --- Begin parameters checking code ----------------------------- Debug.Assert(dependsOnObjects != null); // --- End parameters checking code ------------------------------- // set dependencies Dictionary<T, object> dependencies = _matrix[obj]; dependencies.Clear(); // for each depended objects, add to dependencies foreach (T dependsOnObject in dependsOnObjects) { dependencies.Add(dependsOnObject, null); } } /// <summary> /// Sorts objects based on this dependencies. /// Note: because of the nature of algorithm and memory usage efficiency, this method can be used only one time. /// </summary> public T[] Sort() { // prepare result List<T> result = new List<T>(_matrix.Count); // while there are still object to get while (_matrix.Count > 0) { // get an independent object T independentObject; if (!this.GetIndependentObject(out independentObject)) { // circular dependency found throw new CircularReferenceException(); } // add to result result.Add(independentObject); // delete processed object this.DeleteObject(independentObject); } // return result return result.ToArray(); } #endregion //************************************************** // // Private methods // //************************************************** #region Private methods /// <summary> /// Returns independent object or returns NULL if no independent object is found. /// </summary> private bool GetIndependentObject(out T result) { // for each object foreach (KeyValuePair<T, Dictionary<T, object>> pair in _matrix) { // if the object contains any dependency if (pair.Value.Count > 0) { // has dependency, skip it continue; } // found result = pair.Key; return true; } // not found result = default(T); return false; } /// <summary> /// Deletes given object from the matrix. /// </summary> private void DeleteObject(T obj) { // delete object from matrix _matrix.Remove(obj); // for each object, remove the dependency reference foreach (KeyValuePair<T, Dictionary<T, object>> pair in _matrix) { // if current object depends on deleting object pair.Value.Remove(obj); } } #endregion } /// <summary> /// Represents a circular reference exception when sorting dependency objects. /// </summary> public class CircularReferenceException : Exception { /// <summary> /// Initializes a new instance of the <see cref="CircularReferenceException"/> class. /// </summary> public CircularReferenceException() : base("Circular reference found.") { } } } </code></pre>
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1. POHow to sort depended objects by dependency
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