public static Node MakeHuffmanTree(HashTable<char, int> frequencyTable)
{
//First, create a singly linked list of nodes to return
SLinkedList<Node> looseNodes = new SLinkedList<Node>();
//we need to loop through the given frequency table
SLinkedList<char> keys = frequencyTable.Keys;
for (int i = 0; i < keys.Size; i++) {
//make new node for each element in hash table
Node n = new Node();
//node Data is current key (keys[i])
n.Data = keys[i];
//node frequency is going to be the value for the current key (table[key])
n.Frequency = frequencyTable[keys[i]];
//add this new node to the end(tail) of the loose nodes list
looseNodes.AddTail(n);
}//end loop
/* Comments, no code */
// Next we need to take this loose collection of nodes and build a tree out of it.
// We do this by combining the smallest value nodes under a parent node. Each iteration
// Of the below loop will reduce size by 1, because it removes two nodes and adds one.
// We know we have a tree built, when the loose nodes list has a size of 1.
/* End comments */
//loop while the looseNodes list has more than one element in it
while (looseNodes.Size > 1) {
//make local variable called left and set it to looseNodes[0]
Node left = looseNodes[0];
//we want to set left to the lowest frequency node, loop through nodes
for (int i = 0; i < looseNodes.Size; i++) {
//if frequency of current node is less than left
if (left.Frequency > looseNodes[i].Frequency) {
//set left to current node
left = looseNodes[i];
}//end if
}//end loop
//now that we have a reference to the smallest node, lets remove it from the list
looseNodes.RemoveAt(looseNodes.IndexOf(left));
//Repeat above steps for a new local node called right
Node right = looseNodes[0];
for (int i = 0; i < looseNodes.Size; i++) {
if (right.Frequency > looseNodes[i].Frequency) {
right = looseNodes[i];
}
}
looseNodes.RemoveAt(looseNodes.IndexOf(right));
//Make a new node
Node n = new Node();
//set its left to the local left node
n.Left = right;
//set its right to the local right node
n.Right = left;
//set its frequency to the sum of the left and right nodes frequencies
n.Frequency = right.Frequency + left.Frequency;
//set its data to '\0' (char equivalent of null)
n.Data = '\0';
//Add the new node to the end of the looseNodes list(AddTail)
looseNodes.AddTail(n);
}//end loop
//at this point the loose node list has only one element, and it's the root node of our huffman table
//return [0] of the loose list
return looseNodes[0];
//end loop ?? what loop
}
