public static string Perform(string text)
{
var chars = text.ToCharArray();
// Gathering alphabet frequency
var alphabetFrequency = new Dictionary <char, int>();
foreach (var c in chars) // First pass through the char array
{
if (!alphabetFrequency.ContainsKey(c))
{
alphabetFrequency.Add(c, 1);
}
else
{
alphabetFrequency[c] = alphabetFrequency[c] + 1;
}
}
// Create binary heap
var priorityQueue = new BinaryHeapPriorityQueue <TreeNode>(alphabetFrequency.Count, (i1, i2) => i2.Count.CompareTo(i1.Count));
foreach (var entry in alphabetFrequency)
{
var leafNode = new LeafTreeNode(entry.Value);
CharToNodes.Add(entry.Key, leafNode);
priorityQueue.Insert(leafNode); // Initially PQ contains only leaf nodes
}
// Main part of the algorithm
while (priorityQueue.GetSize() > 1)
{
var n1 = priorityQueue.Extract();
var n2 = priorityQueue.Extract();
var innerNode = new InnerTreeNode(n1, n2); // Creates a new node with sum of frequencies...
priorityQueue.Insert(innerNode); // ...and put it back
} // Repeat the procedure untill PQ has only one element
var root = priorityQueue.Extract(); // Take the last element (root) from the PQ
root.CreateCode(alphabetFrequency.Count == 1 ? "0" : ""); // Build codes for the whole hierarchy
var sb = new StringBuilder();
foreach (var t in chars) // Second pass through the char array
{
var c = CharToNodes[t].Code;
sb.Append(c);
}
return(sb.ToString());
}
public void GetSize_ValidParamsPassed_Success()
{
IPriorityQueue <int> priorityQueue = new BinaryHeapPriorityQueue <int>(5, (x, y) => - x.CompareTo(y));
priorityQueue.Insert(5);
priorityQueue.Insert(4);
priorityQueue.Insert(3);
var size = priorityQueue.GetSize();
Assert.AreEqual(size, 3);
}