/// <summary>
/// Finds the representative of the item's set
/// </summary>
/// <param name="x"></param>
/// <returns></returns>
protected DisjointSetItem Find(DisjointSetItem x)
{
if (x.parent != x)
{
x.parent = Find(x.parent);
}
return(x.parent);
}
/// <summary>
/// Initially all entries are single item sets.
/// </summary>
/// <param name="entries"></param>
public DisjointSets(ISet <T> entries)
{
entriesToItems = new Dictionary <T, DisjointSetItem>();
maxRank = 0;
foreach (var entry in entries)
{
entriesToItems[entry] = new DisjointSetItem();
}
}
/// <summary>
/// Does nothing if entry is already present.
/// Returns whether the entry was really added now.
/// </summary>
public bool AddSet(T entry)
{
if (entriesToItems.ContainsKey(entry) == false)
{
entriesToItems[entry] = new DisjointSetItem();
return(true);
}
return(false);
}
public DisjointSets(DisjointSets <T> other)
{
entriesToItems = new Dictionary <T, DisjointSetItem>();
maxRank = other.maxRank;
var queue = new Queue <T>(other.entriesToItems.Keys);
var otherRepsToNewReps = new Dictionary <DisjointSetItem, DisjointSetItem>();
while (queue.Count != 0)
{
var entry = queue.Dequeue();
var item = other.entriesToItems[entry];
other.Find(item); // Makes item.parent point directly do the set's representative
if (item.parent == item) // This is the set's representative
{
var newItem = new DisjointSetItem();
entriesToItems[entry] = newItem;
// .parent already points to itself as needed
newItem.rank = item.rank; // Since all items in a set do not point directly to the set's rep,
// the set's rank would have been 1 regardless of its size, had it
// been created by calls to Union. We prefer to remember the original rank.
otherRepsToNewReps[item] = newItem;
}
else
{
if (otherRepsToNewReps.ContainsKey(item.parent)) // We've copied this rep already
{
var newItem = new DisjointSetItem();
entriesToItems[entry] = newItem;
newItem.parent = otherRepsToNewReps[item.parent];
// .rank not important in non-rep items
}
else
{
queue.Enqueue(entry); // Wait for the rep to be copied first.
}
}
}
}
public DisjointSetItem()
{
parent = this;
rank = 0;
}
