//******************************
// Written by Peter Golde
// Copyright (c) 2004-2005, Wintellect
//
// Use and restribution of this code is subject to the license agreement
// contained in the file "License.txt" accompanying this file.
//******************************
using System;
using System.Collections.Generic;
using System.Collections;
using System.Diagnostics;
namespace Wintellect.PowerCollections
{
/// <summary>
/// Set<T> is a collection that contains items of type T.
/// The item are maintained in a haphazard, unpredictable order, and duplicate items are not allowed.
/// </summary>
/// <remarks>
/// <p>The items are compared in one of two ways. If T implements IComparable<T>
/// then the Equals method of that interface will be used to compare items, otherwise the Equals
/// method from Object will be used. Alternatively, an instance of IComparer<T> can be passed
/// to the constructor to use to compare items.</p>
/// <p>Set is implemented as a hash table. Inserting, deleting, and looking up an
/// an element all are done in approximately constant time, regardless of the number of items in the Set.</p>
/// <p><see cref="OrderedSet<T>"/> is similar, but uses comparison instead of hashing, and does maintains
/// the items in sorted order.</p>
///</remarks>
///<seealso cref="OrderedSet<T>"/>
[Serializable]
public class Set<T> : CollectionBase<T>, ICollection<T>, ICloneable
{
// The comparer used to hash/compare items.
private IEqualityComparer<T> equalityComparer;
// The hash table that actually does the work of storing the items.
private Hash<T> hash;
#region Constructors
/// <summary>
/// Creates a new Set. The Equals method and GetHashCode method on T
/// will be used to compare items for equality.
/// </summary>
///<remarks>
/// Items that are null are permitted, and will be sorted before all other items.
///</remarks>
public Set():
this(EqualityComparer<T>.Default)
{
}
/// <summary>
/// Creates a new Set. The Equals and GetHashCode method of the passed comparer object
/// will be used to compare items in this set.
/// </summary>
/// <param name="equalityComparer">An instance of IEqualityComparer<T> that will be used to compare items.</param>
public Set(IEqualityComparer<T> equalityComparer)
{
if (equalityComparer == null)
throw new ArgumentNullException("equalityComparer");
this.equalityComparer = equalityComparer;
hash = new Hash<T>(equalityComparer);
}
/// <summary>
/// Creates a new Set. The Equals method and GetHashCode method on T
/// will be used to compare items for equality.
/// </summary>
///<remarks>
/// Items that are null are permitted.
///</remarks>
/// <param name="collection">A collection with items to be placed into the Set.</param>
public Set(IEnumerable<T> collection):
this(collection, EqualityComparer<T>.Default)
{
}
/// <summary>
/// Creates a new Set. The Equals and GetHashCode method of the passed comparer object
/// will be used to compare items in this set. The set is
/// initialized with all the items in the given collection.
/// </summary>
/// <param name="collection">A collection with items to be placed into the Set.</param>
/// <param name="equalityComparer">An instance of IEqualityComparer<T> that will be used to compare items.</param>
public Set(IEnumerable<T> collection, IEqualityComparer<T> equalityComparer)
: this(equalityComparer)
{
AddMany(collection);
}
/// <summary>
/// Creates a new Set given a comparer and a tree that contains the data. Used
/// internally for Clone.
/// </summary>
/// <param name="equalityComparer">EqualityComparer for the set.</param>
/// <param name="hash">Data for the set.</param>
private Set(IEqualityComparer<T> equalityComparer, Hash<T> hash)
{
this.equalityComparer = equalityComparer;
this.hash = hash;
}
#endregion Constructors
#region Cloning
/// <summary>
/// Makes a shallow clone of this set; i.e., if items of the
/// set are reference types, then they are not cloned. If T is a value type,
/// then each element is copied as if by simple assignment.
/// </summary>
/// <remarks>Cloning the set takes time O(N), where N is the number of items in the set.</remarks>
/// <returns>The cloned set.</returns>
object ICloneable.Clone()
{
return this.Clone();
}
/// <summary>
/// Makes a shallow clone of this set; i.e., if items of the
/// set are reference types, then they are not cloned. If T is a value type,
/// then each element is copied as if by simple assignment.
/// </summary>
/// <remarks>Cloning the set takes time O(N), where N is the number of items in the set.</remarks>
/// <returns>The cloned set.</returns>
public Set<T> Clone()
{
Set<T> newSet = new Set<T>(equalityComparer, hash.Clone(null));
return newSet;
}
/// <summary>
/// Makes a deep clone of this set. A new set is created with a clone of
/// each element of this set, by calling ICloneable.Clone on each element. If T is
/// a value type, then each element is copied as if by simple assignment.
/// </summary>
/// <remarks><para>If T is a reference type, it must implement
/// ICloneable. Otherwise, an InvalidOperationException is thrown.</para>
/// <para>Cloning the set takes time O(N), where N is the number of items in the set.</para></remarks>
/// <returns>The cloned set.</returns>
/// <exception cref="InvalidOperationException">T is a reference type that does not implement ICloneable.</exception>
public Set<T> CloneContents()
{
bool itemIsValueType;
if (!Util.IsCloneableType(typeof(T), out itemIsValueType))
throw new InvalidOperationException(string.Format(Strings.TypeNotCloneable, typeof(T).FullName));
Set<T> clone = new Set<T>(equalityComparer);
// Clone each item, and add it to the new ordered set.
foreach (T item in this) {
T itemClone;
if (itemIsValueType)
itemClone = item;
else {
if (item == null)
itemClone = default(T); // Really null, because we know T is a reference type
else
itemClone = (T)(((ICloneable)item).Clone());
}
clone.Add(itemClone);
}
return clone;
}
#endregion Cloning
#region Basic collection containment
/// <summary>
/// Returns the IEqualityComparer<T> used to compare items in this set.
/// </summary>
/// <value>If the set was created using a comparer, that comparer is returned. Otherwise
/// the default comparer for T (EqualityComparer<T>.Default) is returned.</value>
public IEqualityComparer<T> Comparer
{
get
{
return this.equalityComparer;
}
}
/// <summary>
/// Returns the number of items in the set.
/// </summary>
/// <remarks>The size of the set is returned in constant time.</remarks>
/// <value>The number of items in the set.</value>
public sealed override int Count
{
get
{
return hash.ElementCount;
}
}
/// <summary>
/// Returns an enumerator that enumerates all the items in the set.
/// The items are enumerated in sorted order.
/// </summary>
/// <remarks>
/// <p>Typically, this method is not called directly. Instead the "foreach" statement is used
/// to enumerate the items, which uses this method implicitly.</p>
/// <p>If an item is added to or deleted from the set while it is being enumerated, then
/// the enumeration will end with an InvalidOperationException.</p>
/// <p>Enumerating all the items in the set takes time O(N), where N is the number
/// of items in the set.</p>
/// </remarks>
/// <returns>An enumerator for enumerating all the items in the Set.</returns>
public sealed override IEnumerator<T> GetEnumerator()
{
return hash.GetEnumerator();
}
/// <summary>
/// Determines if this set contains an item equal to <paramref name="item"/>. The set
/// is not changed.
/// </summary>
/// <remarks>Searching the set for an item takes approximately constant time, regardless of the number of items in the set.</remarks>
/// <param name="item">The item to search for.</param>
/// <returns>True if the set contains <paramref name="item"/>. False if the set does not contain <paramref name="item"/>.</returns>
public sealed override bool Contains(T item)
{
T dummy;
return hash.Find(item, false, out dummy);
}
/// <summary>
/// <para>Determines if this set contains an item equal to <paramref name="item"/>, according to the
/// comparison mechanism that was used when the set was created. The set
/// is not changed.</para>
/// <para>If the set does contain an item equal to <paramref name="item"/>, then the item from the set is returned.</para>
/// </summary>
/// <remarks>Searching the set for an item takes approximately constant time, regardless of the number of items in the set.</remarks>
/// <example>
/// In the following example, the set contains strings which are compared in a case-insensitive manner.
/// <code>
/// Set<string> set = new Set<string>(StringComparer.CurrentCultureIgnoreCase);
/// set.Add("HELLO");
/// string s;
/// bool b = set.TryGetItem("Hello", out s); // b receives true, s receives "HELLO".
/// </code>
/// </example>
/// <param name="item">The item to search for.</param>
/// <param name="foundItem">Returns the item from the set that was equal to <paramref name="item"/>.</param>
/// <returns>True if the set contains <paramref name="item"/>. False if the set does not contain <paramref name="item"/>.</returns>
public bool TryGetItem(T item, out T foundItem)
{
return hash.Find(item, false, out foundItem);
}
#endregion
#region Adding elements
/// <summary>
/// Adds a new item to the set. If the set already contains an item equal to
/// <paramref name="item"/>, that item is replaced with <paramref name="item"/>.
/// </summary>
/// <remarks>
/// <para>Equality between items is determined by the comparison instance or delegate used
/// to create the set.</para>
/// <para>Adding an item takes approximately constant time, regardless of the number of items in the set.</para></remarks>
/// <param name="item">The item to add to the set.</param>
/// <returns>True if the set already contained an item equal to <paramref name="item"/> (which was replaced), false
/// otherwise.</returns>
public new bool Add(T item)
{
T dummy;
return !hash.Insert(item, true, out dummy);
}
/// <summary>
/// Adds a new item to the set. If the set already contains an item equal to
/// <paramref name="item"/>, that item is replaced with <paramref name="item"/>.
/// </summary>
/// <remarks>
/// <para>Equality between items is determined by the comparison instance or delegate used
/// to create the set.</para>
/// <para>Adding an item takes approximately constant time, regardless of the number of items in the set.</para></remarks>
/// <param name="item">The item to add to the set.</param>
/// <returns>True if the set already contained an item equal to <paramref name="item"/> (which was replaced), false
/// otherwise.</returns>
void ICollection<T>.Add(T item)
{
Add(item);
}
/// <summary>
/// Adds all the items in <paramref name="collection"/> to the set. If the set already contains an item equal to
/// one of the items in <paramref name="collection"/>, that item will be replaced.
/// </summary>
/// <remarks>
/// <para>Equality between items is determined by the comparison instance or delegate used
/// to create the set.</para>
/// <para>Adding the collection takes time O(M), where M is the
/// number of items in <paramref name="collection"/>.</para></remarks>
/// <param name="collection">A collection of items to add to the set.</param>
public void AddMany(IEnumerable<T> collection)
{
if (collection == null)
throw new ArgumentNullException("collection");
// If we're adding ourselves, then there is nothing to do.
if (object.ReferenceEquals(collection, this))
return;
foreach (T item in collection)
Add(item);
}
#endregion Adding elements
#region Removing elements
/// <summary>
/// Searches the set for an item equal to <paramref name="item"/>, and if found,
/// removes it from the set. If not found, the set is unchanged.
/// </summary>
/// <remarks>
/// <para>Equality between items is determined by the comparison instance or delegate used
/// to create the set.</para>
/// <para>Removing an item from the set takes approximately constant time, regardless of the size of the set.</para></remarks>
/// <param name="item">The item to remove.</param>
/// <returns>True if <paramref name="item"/> was found and removed. False if <paramref name="item"/> was not in the set.</returns>
public sealed override bool Remove(T item)
{
T dummy;
return hash.Delete(item, out dummy);
}
/// <summary>
/// Removes all the items in <paramref name="collection"/> from the set.
/// </summary>
/// <remarks>
/// <para>Equality between items is determined by the comparison instance or delegate used
/// to create the set.</para>
/// <para>Removing the collection takes time O(M), where M is the
/// number of items in <paramref name="collection"/>.</para></remarks>
/// <param name="collection">A collection of items to remove from the set.</param>
/// <returns>The number of items removed from the set.</returns>
/// <exception cref="ArgumentNullException"><paramref name="collection"/> is null.</exception>
public int RemoveMany(IEnumerable<T> collection)
{
if (collection == null)
throw new ArgumentNullException("collection");
int count = 0;
if (collection == this) {
count = Count;
Clear(); // special case, otherwise we will throw.
}
else {
foreach (T item in collection) {
if (Remove(item))
++count;
}
}
return count;
}
/// <summary>
/// Removes all items from the set.
/// </summary>
/// <remarks>Clearing the set takes a constant amount of time, regardless of the number of items in it.</remarks>
public sealed override void Clear()
{
hash.StopEnumerations(); // Invalidate any enumerations.
// The simplest and fastest way is simply to throw away the old tree and create a new one.
hash = new Hash<T>(equalityComparer);
}
#endregion Removing elements
#region Set operations
/// <summary>
/// Check that this set and another set were created with the same comparison
/// mechanism. Throws exception if not compatible.
/// </summary>
/// <param name="otherSet">Other set to check comparision mechanism.</param>
/// <exception cref="InvalidOperationException">If otherSet and this set don't use the same method for comparing items.</exception>
private void CheckConsistentComparison(Set<T> otherSet)
{
if (otherSet == null)
throw new ArgumentNullException("otherSet");
if (!object.Equals(equalityComparer, otherSet.equalityComparer))
throw new InvalidOperationException(Strings.InconsistentComparisons);
}
/// <summary>
/// Determines if this set is a superset of another set. Neither set is modified.
/// This set is a superset of <paramref name="otherSet"/> if every element in
/// <paramref name="otherSet"/> is also in this set.
/// <remarks>IsSupersetOf is computed in time O(M), where M is the size of the
/// <paramref name="otherSet"/>.</remarks>
/// </summary>
/// <param name="otherSet">Set to compare to.</param>
/// <returns>True if this is a superset of <paramref name="otherSet"/>.</returns>
/// <exception cref="InvalidOperationException">This set and <paramref name="otherSet"/> don't use the same method for comparing items.</exception>
public bool IsSupersetOf(Set<T> otherSet)
{
CheckConsistentComparison(otherSet);
if (otherSet.Count > this.Count)
return false; // Can't be a superset of a bigger set
// Check each item in the other set to make sure it is in this set.
foreach (T item in otherSet) {
if (!this.Contains(item))
return false;
}
return true;
}
/// <summary>
/// Determines if this set is a proper superset of another set. Neither set is modified.
/// This set is a proper superset of <paramref name="otherSet"/> if every element in
/// <paramref name="otherSet"/> is also in this set.
/// Additionally, this set must have strictly more items than <paramref name="otherSet"/>.
/// </summary>
/// <remarks>IsProperSubsetOf is computed in time O(M), where M is the size of
/// <paramref name="otherSet"/>.</remarks>
/// <param name="otherSet">Set to compare to.</param>
/// <returns>True if this is a proper superset of <paramref name="otherSet"/>.</returns>
/// <exception cref="InvalidOperationException">This set and <paramref name="otherSet"/> don't use the same method for comparing items.</exception>
public bool IsProperSupersetOf(Set<T> otherSet)
{
CheckConsistentComparison(otherSet);
if (otherSet.Count >= this.Count)
return false; // Can't be a proper superset of a bigger or equal set
return IsSupersetOf(otherSet);
}
/// <summary>
/// Determines if this set is a subset of another set. Neither set is modified.
/// This set is a subset of <paramref name="otherSet"/> if every element in this set
/// is also in <paramref name="otherSet"/>.
/// </summary>
/// <remarks>IsSubsetOf is computed in time O(N), where N is the size of the this set.</remarks>
/// <param name="otherSet">Set to compare to.</param>
/// <returns>True if this is a subset of <paramref name="otherSet"/>.</returns>
/// <exception cref="InvalidOperationException">This set and <paramref name="otherSet"/> don't use the same method for comparing items.</exception>
public bool IsSubsetOf(Set<T> otherSet)
{
return otherSet.IsSupersetOf(this);
}
/// <summary>
/// Determines if this set is a proper subset of another set. Neither set is modified.
/// This set is a subset of <paramref name="otherSet"/> if every element in this set
/// is also in <paramref name="otherSet"/>. Additionally, this set must have strictly
/// fewer items than <paramref name="otherSet"/>.
/// </summary>
/// <remarks>IsProperSubsetOf is computed in time O(N), where N is the size of the this set.</remarks>
/// <param name="otherSet">Set to compare to.</param>
/// <returns>True if this is a proper subset of <paramref name="otherSet"/>.</returns>
/// <exception cref="InvalidOperationException">This set and <paramref name="otherSet"/> don't use the same method for comparing items.</exception>
public bool IsProperSubsetOf(Set<T> otherSet)
{
return otherSet.IsProperSupersetOf(this);
}
/// <summary>
/// Determines if this set is equal to another set. This set is equal to
/// <paramref name="otherSet"/> if they contain the same items.
/// </summary>
/// <remarks>IsEqualTo is computed in time O(N), where N is the number of items in
/// this set.</remarks>
/// <param name="otherSet">Set to compare to</param>
/// <returns>True if this set is equal to <paramref name="otherSet"/>, false otherwise.</returns>
/// <exception cref="InvalidOperationException">This set and <paramref name="otherSet"/> don't use the same method for comparing items.</exception>
public bool IsEqualTo(Set<T> otherSet)
{
CheckConsistentComparison(otherSet);
// Must be the same size.
if (otherSet.Count != this.Count)
return false;
// Check each item in the other set to make sure it is in this set.
foreach (T item in otherSet) {
if (!this.Contains(item))
return false;
}
return true;
}
/// <summary>
/// Determines if this set is disjoint from another set. Two sets are disjoint
/// if no item from one set is equal to any item in the other set.
/// </summary>
/// <remarks>
/// <para>The answer is computed in time O(N), where N is the size of the smaller set.</para>
/// </remarks>
/// <param name="otherSet">Set to check disjointness with.</param>
/// <returns>True if the two sets are disjoint, false otherwise.</returns>
/// <exception cref="InvalidOperationException">This set and <paramref name="otherSet"/> don't use the same method for comparing items.</exception>
public bool IsDisjointFrom(Set<T> otherSet)
{
CheckConsistentComparison(otherSet);
Set<T> smaller, larger;
if (otherSet.Count > this.Count) {
smaller = this; larger = otherSet;
}
else {
smaller = otherSet; larger = this;
}
foreach (T item in smaller) {
if (larger.Contains(item))
return false;
}
return true;
}
/// <summary>
/// Computes the union of this set with another set. The union of two sets
/// is all items that appear in either or both of the sets. This set receives
/// the union of the two sets, the other set is unchanged.
/// </summary>
/// <remarks>
/// <para>If equal items appear in both sets, the union will include an arbitrary choice of one of the
/// two equal items.</para>
/// <para>The union of two sets is computed in time O(M + N), where M is the size of the
/// larger set, and N is the size of the smaller set.</para>
/// </remarks>
/// <param name="otherSet">Set to union with.</param>
/// <exception cref="InvalidOperationException">This set and <paramref name="otherSet"/> don't use the same method for comparing items.</exception>
public void UnionWith(Set<T> otherSet)
{
CheckConsistentComparison(otherSet);
AddMany(otherSet);
}
/// <summary>
/// Computes the union of this set with another set. The union of two sets
/// is all items that appear in either or both of the sets. A new set is
/// created with the union of the sets and is returned. This set and the other set
/// are unchanged.
/// </summary>
/// <remarks>
/// <para>If equal items appear in both sets, the union will include an arbitrary choice of one of the
/// two equal items.</para>
/// <para>The union of two sets is computed in time O(M + N), where M is the size of the
/// one set, and N is the size of the other set.</para>
/// </remarks>
/// <param name="otherSet">Set to union with.</param>
/// <returns>The union of the two sets.</returns>
/// <exception cref="InvalidOperationException">This set and <paramref name="otherSet"/> don't use the same method for comparing items.</exception>
public Set<T> Union(Set<T> otherSet)
{
CheckConsistentComparison(otherSet);
Set<T> smaller, larger, result;
if (otherSet.Count > this.Count) {
smaller = this; larger = otherSet;
}
else {
smaller = otherSet; larger = this;
}
result = larger.Clone();
result.AddMany(smaller);
return result;
}
/// <summary>
/// Computes the intersection of this set with another set. The intersection of two sets
/// is all items that appear in both of the sets. This set receives
/// the intersection of the two sets, the other set is unchanged.
/// </summary>
/// <remarks>
/// <para>When equal items appear in both sets, the intersection will include an arbitrary choice of one of the
/// two equal items.</para>
/// <para>The intersection of two sets is computed in time O(N), where N is the size of the smaller set.</para>
/// </remarks>
/// <param name="otherSet">Set to intersection with.</param>
/// <exception cref="InvalidOperationException">This set and <paramref name="otherSet"/> don't use the same method for comparing items.</exception>
public void IntersectionWith(Set<T> otherSet)
{
CheckConsistentComparison(otherSet);
hash.StopEnumerations();
Set<T> smaller, larger;
if (otherSet.Count > this.Count) {
smaller = this; larger = otherSet;
}
else {
smaller = otherSet; larger = this;
}
T dummy;
Hash<T> newHash = new Hash<T>(equalityComparer);
foreach (T item in smaller) {
if (larger.Contains(item))
newHash.Insert(item, true, out dummy);
}
hash = newHash;
}
/// <summary>
/// Computes the intersection of this set with another set. The intersection of two sets
/// is all items that appear in both of the sets. A new set is
/// created with the intersection of the sets and is returned. This set and the other set
/// are unchanged.
/// </summary>
/// <remarks>
/// <para>When equal items appear in both sets, the intersection will include an arbitrary choice of one of the
/// two equal items.</para>
/// <para>The intersection of two sets is computed in time O(N), where N is the size of the smaller set.</para>
/// </remarks>
/// <param name="otherSet">Set to intersection with.</param>
/// <returns>The intersection of the two sets.</returns>
/// <exception cref="InvalidOperationException">This set and <paramref name="otherSet"/> don't use the same method for comparing items.</exception>
public Set<T> Intersection(Set<T> otherSet)
{
CheckConsistentComparison(otherSet);
Set<T> smaller, larger, result;
if (otherSet.Count > this.Count) {
smaller = this; larger = otherSet;
}
else {
smaller = otherSet; larger = this;
}
result = new Set<T>(equalityComparer);
foreach (T item in smaller) {
if (larger.Contains(item))
result.Add(item);
}
return result;
}
/// <summary>
/// Computes the difference of this set with another set. The difference of these two sets
/// is all items that appear in this set, but not in <paramref name="otherSet"/>. This set receives
/// the difference of the two sets; the other set is unchanged.
/// </summary>
/// <remarks>
/// <para>The difference of two sets is computed in time O(N), where N is the size of the smaller set.</para>
/// </remarks>
/// <param name="otherSet">Set to difference with.</param>
/// <exception cref="InvalidOperationException">This set and <paramref name="otherSet"/> don't use the same method for comparing items.</exception>
public void DifferenceWith(Set<T> otherSet)
{
// Difference with myself is nothing. This check is needed because the
// main algorithm doesn't work correctly otherwise.
if (this == otherSet)
Clear();
CheckConsistentComparison(otherSet);
if (otherSet.Count < this.Count) {
foreach (T item in otherSet) {
this.Remove(item);
}
}
else {
RemoveAll(delegate(T item) { return otherSet.Contains(item); });
}
}
/// <summary>
/// Computes the difference of this set with another set. The difference of these two sets
/// is all items that appear in this set, but not in <paramref name="otherSet"/>. A new set is
/// created with the difference of the sets and is returned. This set and the other set
/// are unchanged.
/// </summary>
/// <remarks>
/// <para>The difference of two sets is computed in time O(N), where N is the size of the smaller set.</para>
/// </remarks>
/// <param name="otherSet">Set to difference with.</param>
/// <returns>The difference of the two sets.</returns>
/// <exception cref="InvalidOperationException">This set and <paramref name="otherSet"/> don't use the same method for comparing items.</exception>
public Set<T> Difference(Set<T> otherSet)
{
CheckConsistentComparison(otherSet);
Set<T> result = this.Clone();
result.DifferenceWith(otherSet);
return result;
}
/// <summary>
/// Computes the symmetric difference of this set with another set. The symmetric difference of two sets
/// is all items that appear in either of the sets, but not both. This set receives
/// the symmetric difference of the two sets; the other set is unchanged.
/// </summary>
/// <remarks>
/// <para>The symmetric difference of two sets is computed in time O(N), where N is the size of the smaller set.</para>
/// </remarks>
/// <param name="otherSet">Set to symmetric difference with.</param>
/// <exception cref="InvalidOperationException">This set and <paramref name="otherSet"/> don't use the same method for comparing items.</exception>
public void SymmetricDifferenceWith(Set<T> otherSet)
{
// main algorithm doesn't work correctly otherwise.
if (this == otherSet)
Clear();
CheckConsistentComparison(otherSet);
if (otherSet.Count > this.Count) {
hash.StopEnumerations();
Hash<T> newHash = otherSet.hash.Clone(null);
T dummy;
foreach (T item in this) {
if (newHash.Find(item, false, out dummy))
newHash.Delete(item, out dummy);
else
newHash.Insert(item, true, out dummy);
}
this.hash = newHash;
}
else {
foreach (T item in otherSet) {
if (this.Contains(item))
this.Remove(item);
else
this.Add(item);
}
}
}
/// <summary>
/// Computes the symmetric difference of this set with another set. The symmetric difference of two sets
/// is all items that appear in either of the sets, but not both. A new set is
/// created with the symmetric difference of the sets and is returned. This set and the other set
/// are unchanged.
/// </summary>
/// <remarks>
/// <para>The symmetric difference of two sets is computed in time O(N), where N is the size of the smaller set.</para>
/// </remarks>
/// <param name="otherSet">Set to symmetric difference with.</param>
/// <returns>The symmetric difference of the two sets.</returns>
/// <exception cref="InvalidOperationException">This set and <paramref name="otherSet"/> don't use the same method for comparing items.</exception>
public Set<T> SymmetricDifference(Set<T> otherSet)
{
CheckConsistentComparison(otherSet);
Set<T> smaller, larger, result;
if (otherSet.Count > this.Count) {
smaller = this; larger = otherSet;
}
else {
smaller = otherSet; larger = this;
}
result = larger.Clone();
foreach (T item in smaller) {
if (result.Contains(item))
result.Remove(item);
else
result.Add(item);
}
return result;
}
#endregion Set operations
}
}