public HuffmanTree(String code)
{
CodeWord = code;
char[] letters = code.ToCharArray();
int[] frequency = new int[53];
for (int i = 0; i < code.Length; i++) // adds once to the corresponding letters index each time it occurs in the codeword
{
if (letters[i] > 64 && letters[i] < 91) // capital letters numeric value
{
frequency[letters[i] - 65]++; // indexs 0-25
}
if (letters[i] > 96 && letters[i] < 123) // lower case letters numeric value
{
frequency[letters[i] + 26 - 97]++; // index 0-25 used
}
if (letters[i] == 32) // space numeric value
{
frequency[52]++; // last unused index;
}
}
PriorityQueue <BinaryTree <Data> > pQueue = new PriorityQueue <BinaryTree <Data> >(53);
Data data;
BinaryTree <Data> BT;
for (int i = 0; i < 53; i++) // for each possible char
{
if (frequency[i] != 0) // if the frequency is not null
{
if (i < 26) // if capital letter create binary tree with its value and frequency inside the root node
{
data = new Data(i + 65, frequency[i]); //(i +65 gives numeric value of char)
BT = new BinaryTree <Data>();
BT.Add(data);
pQueue.Add(BT);
}
if (i > 25 && i < 52) // if lower case letter create ""
{
data = new Data(i + 97 - 26, frequency[i]); //(i+97-26) gives numeric value of char
BT = new BinaryTree <Data>();
BT.Add(data);
pQueue.Add(BT);
}
if (i == 52) // if space
{
data = new Data(32, frequency[i]); // 32 is numeric value of space
BT = new BinaryTree <Data>();
BT.Add(data);
pQueue.Add(BT);
}
}
}
Build(pQueue); // build Huffman tree from pQueue of BT<Data>
}
private void Build(PriorityQueue <BinaryTree <Data> > pQueue)
{
BinaryTree <Data> BT = new BinaryTree <Data>();;
BinaryTree <Data> BT1;
BinaryTree <Data> BT2;
Data data;
while (pQueue.Size() > 1) // when only 1 value is in pQueue then it is the completed huffman tree
{
BT1 = pQueue.Front(); // get first element from pQueue
pQueue.Remove();
BT2 = pQueue.Front(); // get Second element from pQueue
pQueue.Remove();
BT = new BinaryTree <Data>(); // create a new binary tree
data = new Data(BT1.Root.Item.Frequency + BT2.Root.Item.Frequency);
BT.Add(data); // set its root to be the value of BT1 and BT2 combined frequency
if (BT1.Root.Item.Frequency == BT2.Root.Item.Frequency) // doesnt matter but place larger trees on left
{
if (BT1.Size() < BT2.Size()) // compare size of trees with equal frequency
{
BT.Root.Left = BT2.Root; // large tree left
BT.Root.Right = BT1.Root; // smaller tree right
}
else
{
BT.Root.Left = BT1.Root; // larger tree right
BT.Root.Right = BT2.Root; // smalller tree left
}
}
else // not equal frequency
{
BT.Root.Left = BT1.Root; // first tree removed has smaller frequency and is placed on left
BT.Root.Right = BT2.Root; // second tree removed has larger frequency and is placed on right
}
pQueue.Add(BT); // add the new Binary tree to the Priority Queue
}
this.Root = BT.Root; // set Huffman tree root the the new BT that now is a completed huffman tree
}