/// <summary>
/// Returns a dictionary of chosen encoding bytes for each distinct T.
/// </summary>
public Dictionary <T, byte[]> Compress(T[] input)
{
var frequencies = computeFrequency(input);
var minHeap = new BHeap <FrequencyWrap>();
foreach (var frequency in frequencies)
{
minHeap.Insert(new FrequencyWrap(
frequency.Key, frequency.Value));
}
while (minHeap.Count > 1)
{
var a = minHeap.Extract();
var b = minHeap.Extract();
var newNode = new FrequencyWrap(
default(T), a.Frequency + b.Frequency);
newNode.Left = a;
newNode.Right = b;
minHeap.Insert(newNode);
}
var root = minHeap.Extract();
var result = new Dictionary <T, byte[]>();
dfs(root, new List <byte>(), result);
return(result);
}
/// <summary>
/// Now gather the codes.
/// </summary>
private void dfs(FrequencyWrap currentNode, List <byte> pathStack, Dictionary <T, byte[]> result)
{
if (currentNode.IsLeaf)
{
result.Add(currentNode.Item, pathStack.ToArray());
return;
}
if (currentNode.Left != null)
{
pathStack.Add(0);
dfs(currentNode.Left, pathStack, result);
pathStack.RemoveAt(pathStack.Count - 1);
}
if (currentNode.Right != null)
{
pathStack.Add(1);
dfs(currentNode.Right, pathStack, result);
pathStack.RemoveAt(pathStack.Count - 1);
}
}
