public bool Equals(HashSet <T>?x, HashSet <T>?y)
{
// If they're the exact same instance, they're equal.
if (ReferenceEquals(x, y))
{
return(true);
}
// They're not both null, so if either is null, they're not equal.
if (x == null || y == null)
{
return(false);
}
EqualityComparer <T> defaultComparer = EqualityComparer <T> .Default;
// If both sets use the same comparer, they're equal if they're the same
// size and one is a "subset" of the other.
if (HashSet <T> .EqualityComparersAreEqual(x, y))
{
return(x.Count == y.Count && y.IsSubsetOfHashSetWithSameComparer(x));
}
// Otherwise, do an O(N^2) match.
foreach (T yi in y)
{
bool found = false;
foreach (T xi in x)
{
if (defaultComparer.Equals(yi, xi))
{
found = true;
break;
}
}
if (!found)
{
return(false);
}
}
return(true);
}
