/// <summary>
/// Computes the intersection of this bag with another bag. The intersection of two bags
/// is all items that appear in both of the bags. If an item appears X times in one bag,
/// and Y times in the other bag, the intersection contains the item Minimum(X,Y) times. A new bag is
/// created with the intersection of the bags and is returned. This bag and the other bag
/// are unchanged.
/// </summary>
/// <remarks>
/// <para>When equal items appear in both bags, the intersection will include an arbitrary choice of one of the
/// two equal items.</para>
/// <para>The intersection of two bags is computed in time O(N), where N is the size of the smaller bag.</para>
/// </remarks>
/// <param name="otherBag">Bag to intersection with.</param>
/// <returns>The intersection of the two bags.</returns>
/// <exception cref="InvalidOperationException">This bag and <paramref name="otherBag"/> don't use the same method for comparing items.</exception>
public Bag <T> Intersection(Bag <T> otherBag)
{
CheckConsistentComparison(otherBag);
Bag <T> smaller, larger;
if (otherBag.Count > Count)
{
smaller = this;
larger = otherBag;
}
else
{
smaller = otherBag;
larger = this;
}
// Enumerate each of the items in the smaller bag. Add items that need to be
// added to the intersection.
var result = new Bag <T>(_keyEqualityComparer);
foreach (var item in smaller.DistinctItems())
{
var copiesInLarger = larger.NumberOfCopies(item);
var copiesInSmaller = smaller.NumberOfCopies(item);
var copies = Math.Min(copiesInLarger, copiesInSmaller);
if (copies > 0)
{
result.ChangeNumberOfCopies(item, copies);
}
}
return(result);
}
public void ChangeNumberOfCopies()
{
var bag1 = new Bag <string>(
new[] { "foo", null, "FOO", "Eric", "eric", "bar", null, "foO", "ERIC", "eric", null },
StringComparer.InvariantCultureIgnoreCase);
bag1.ChangeNumberOfCopies("Foo", 7);
bag1.ChangeNumberOfCopies(null, 0);
bag1.ChangeNumberOfCopies("eRIC", 0);
bag1.ChangeNumberOfCopies("silly", 2);
bag1.ChangeNumberOfCopies("BAR", 1);
InterfaceTests.TestReadWriteCollectionGeneric(bag1,
new[]
{ "foo", "foo", "foo", "foo", "foo", "foo", "foo", "bar", "silly", "silly" },
false);
}
