//TODO: Maybe cache?
//Huffman's coding with weight=1 for all. Using the O(n) described on wikipedia.
//
private void GenerateCodes()
{
StateMappings = null;
//one possible state, no need for codes
if (PossibleStates.Count == 1)
return;
StateMappings = new SortedDictionary<string, string>();
LinkedList<Node> startQueue = new LinkedList<Node>();
LinkedList<Node> endQueue = new LinkedList<Node>();
foreach (string state in PossibleStates.Select(x => x.Item1))
{
startQueue.AddLast(new Node { State = state });
}
while (startQueue.Count > 1)
{
Node newNode = new Node();
newNode.LeftChild = startQueue.First();
startQueue.RemoveFirst();
newNode.RightChild = startQueue.First();
startQueue.RemoveFirst();
endQueue.AddLast(newNode);
}
//one left; there must be at least 1 node in endqueue
if (startQueue.Count == 1)
{
Node newNode = new Node();
newNode.LeftChild = startQueue.First();
startQueue.RemoveFirst();
newNode.RightChild = endQueue.First();
endQueue.RemoveFirst();
endQueue.AddLast(newNode);
}
//now we know that startQueue is empty and endqueue has at least 1 node.
while (endQueue.Count > 1)
{
Node newNode = new Node();
newNode.LeftChild = endQueue.First();
endQueue.RemoveFirst();
newNode.RightChild = endQueue.First();
endQueue.RemoveFirst();
endQueue.AddLast(newNode);
}
//now we have 1 node left. the root node.
//now to generate the codes by walking the tree.
string code = "";
BuildCode(endQueue.First(), code);
ShortestCode = StateMappings.Keys.OrderByDescending(s => s.Length).Last().Length;
LongestCode = StateMappings.Keys.OrderByDescending(s => s.Length).First().Length;
}
public Node()
{
rChild = lChild = null;
}
/*private void Count(Node n)
{
if (n == null)
return;
if (n.LeftChild == null && n.RightChild == null)
{
return;
}
Count(n.LeftChild);
Count(n.RightChild);
}*/
private void BuildCode(Node n, string code)
{
//leaf, we need a code
if (n.LeftChild == null && n.RightChild == null)
{
//map it
StateMappings.Add(code, n.State);
}
//if we have a left child, add 0 to the code
if (n.LeftChild != null)
{
BuildCode(n.LeftChild, code + "0");
}
if (n.RightChild != null)
{
BuildCode(n.RightChild, code + "1");
}
}