public HuffmanTree(string binary)
{
Queue<char> bitStream = new Queue<char>();
for (int i = 0; i < binary.Length; ++i) {
bitStream.Enqueue(binary[i]);
}
head = buildTreeFromBinary(bitStream);
populateSearchStrings(head);
}
//Fills the priority queue with the appropriate characters and respective weights
private void populateQueue(char[] charset, int[] weights)
{
topNodes = new PriorityQueue<HuffmanTreeNode>();
for (int i = 0; i < charset.Length; i++) {
HuffmanTreeNode currentNode = new HuffmanTreeNode(Char.ToString(charset[i]));
topNodes.enqueue(currentNode, weights[i]);
}
}
private void populateSearchStrings(HuffmanTreeNode currentNode)
{
string leftCharset = currentNode.Left.Charset;
string rightCharset = currentNode.Right.Charset;
if (leftCharset == "") {
populateSearchStrings(currentNode.Left);
leftCharset = currentNode.Left.Charset;
}
if (rightCharset == "") {
populateSearchStrings(currentNode.Right);
rightCharset = currentNode.Right.Charset;
}
currentNode.Charset = leftCharset + rightCharset;
}
//Returns whether a node is a leaf node or not
private Boolean isLeaf(HuffmanTreeNode node)
{
return node.Left == null && node.Right == null;
}
//constructs a huffman tree from a priority queue of characters
private void buildHuffmanTree()
{
while (topNodes.length() > 1) {
int node1Priority = topNodes.lowestPriority();
HuffmanTreeNode node1 = topNodes.dequeueLowest();
int node2Priority = topNodes.lowestPriority();
HuffmanTreeNode node2 = topNodes.dequeueLowest();
HuffmanTreeNode newNode = new HuffmanTreeNode(node1.Charset + node2.Charset, node1, node2);
topNodes.enqueue(newNode, node1Priority + node2Priority);
}
head = topNodes.dequeueHighest();
}
//process for getBinaryRepresentation()
//getBinaryRepresentation() is a public interface method which hides the starting parameters of this recursive process from the user
private string buildBinaryString(HuffmanTreeNode currentNode)
{
if (currentNode == null) {
return "";
}
if (isLeaf(currentNode)) {
byte[] bytes = Encoding.ASCII.GetBytes(currentNode.Charset);
byte charValue = bytes[0];
string binary = Convert.ToString(charValue, 2).PadLeft(7, '0');
return "1" + binary;
} else {
return "0" + buildBinaryString(currentNode.Left) + buildBinaryString(currentNode.Right);
}
}
//constructs leaf node with specified charset
public HuffmanTreeNode(string charset)
{
this.charset = charset;
this.left = null;
this.right = null;
}
//general use constructor
public HuffmanTreeNode(string charset, HuffmanTreeNode left, HuffmanTreeNode right)
{
this.charset = charset;
this.left = left;
this.right = right;
}