/// <summary>
/// Extract the item of the root
/// </summary>
/// <returns></returns>
public IPriorityQueueNode <K, T> Pop()
{
IPriorityQueueNode <K, T> item = _data[0];
Size--;
_data[0] = _data[Size];
HeapifyDown(0);
return(item);
}
/// <summary>
/// Add an item to the heap
/// </summary>
/// <param name="item"></param>
public void Insert(IPriorityQueueNode <K, T> item)
{
if (Size == _data.Length)
{
Resize();
}
_data[Size] = item;
HeapifyUp(Size);
Size++;
}
public int CompareTo(IPriorityQueueNode <K, T> other)
{
if (Priority.CompareTo(other.Priority) < 0)
{
return(-1);
}
else if (Priority.CompareTo(other.Priority) > 0)
{
return(1);
}
return(0);
}
private void HeapifyUp(int childIdx)
{
if (childIdx > 0)
{
int parentIdx = (childIdx - 1) / 2;
if (_comparison.Invoke(_data[childIdx].Priority, _data[parentIdx].Priority) > 0)
{
// swap parent and child
IPriorityQueueNode <K, T> t = _data[parentIdx];
_data[parentIdx] = _data[childIdx];
_data[childIdx] = t;
HeapifyUp(parentIdx);
}
}
}
private void HeapifyDown(int parentIdx)
{
int leftChildIdx = 2 * parentIdx + 1;
int rightChildIdx = leftChildIdx + 1;
int largestChildIdx = parentIdx;
if (leftChildIdx < Size && _comparison.Invoke(_data[leftChildIdx].Priority, _data[largestChildIdx].Priority) > 0)
{
largestChildIdx = leftChildIdx;
}
if (rightChildIdx < Size && _comparison.Invoke(_data[rightChildIdx].Priority, _data[largestChildIdx].Priority) > 0)
{
largestChildIdx = rightChildIdx;
}
if (largestChildIdx != parentIdx)
{
IPriorityQueueNode <K, T> t = _data[parentIdx];
_data[parentIdx] = _data[largestChildIdx];
_data[largestChildIdx] = t;
HeapifyDown(largestChildIdx);
}
}
private void Resize()
{
IPriorityQueueNode <K, T>[] resizedData = new IPriorityQueueNode <K, T> [_data.Length * 2];
Array.Copy(_data, 0, resizedData, 0, _data.Length);
_data = resizedData;
}
