/// <summary>
/// Removes a node from the queue. The node does not need to be the head of the
/// queue. This is an O(log n) operation.
/// </summary>
///
public void Remove(PriorityQueueNode <T> node)
{
#if DEBUG
if (!Contains(node))
{
throw new InvalidOperationException("Cannot call Remove() on a node which is not enqueued: " + node);
}
#endif
CheckQueue();
// If the node is already the last node, we can remove it immediately
if (node.QueueIndex == numberOfNodes)
{
nodes[numberOfNodes] = PriorityQueueNode <T> .Empty;
numberOfNodes--;
return;
}
int index = node.QueueIndex;
// Swap the node with the last node
swap(node.QueueIndex, numberOfNodes);
nodes[numberOfNodes] = PriorityQueueNode <T> .Empty;
numberOfNodes--;
// Now bubble formerLastNode (which is no longer the last node) up or down as appropriate
OnNodeUpdated(ref nodes[index]);
CheckQueue();
}
/// <summary>
/// Compares the current object with another object of the same type.
/// </summary>
/// <param name="other">An object to compare with this object.</param>
/// <returns>
/// A value that indicates the relative order of the objects being compared. The return value has the following meanings: Value Meaning Less than zero This object is less than the <paramref name="other" /> parameter.Zero This object is equal to <paramref name="other" />. Greater than zero This object is greater than <paramref name="other" />.
/// </returns>
public int CompareTo(PriorityQueueNode <T> other)
{
int order = this.Priority.CompareTo(other.Priority);
if (order == 0)
{
order = this.InsertionIndex.CompareTo(other.InsertionIndex);
}
return(order);
}
public bool Contains(PriorityQueueNode <T> node)
{
#if DEBUG
if (node.QueueIndex < 0 || node.QueueIndex >= nodes.Length)
{
throw new InvalidOperationException("node.QueueIndex has been corrupted. Did you change it manually? Or add this node to another queue?");
}
#endif
return(nodes[node.QueueIndex] == node);
}
public void UpdatePriority(ref PriorityQueueNode <T> node, double priority)
{
#if DEBUG
if (!Contains(node))
{
throw new InvalidOperationException("Cannot call UpdatePriority() on a node which is not enqueued: " + node);
}
#endif
node.Priority = priority;
OnNodeUpdated(ref node);
}
/// <summary>
/// Returns an array containing the items in this list,
/// optionally in in priority order.
/// </summary>
///
/// <param name="sorted">Whether to return the items in priority order.</param>
///
public PriorityQueueNode <T>[] ToArray(bool sorted = true)
{
var result = new PriorityQueueNode <T> [numberOfNodes];
for (int i = 0; i < result.Length; i++)
{
result[i] = nodes[i + 1];
}
if (sorted)
{
Array.Sort(result);
}
return(result);
}
private void OnNodeUpdated(ref PriorityQueueNode <T> node)
{
// Bubble the updated node up or down as appropriate
int parentIndex = node.QueueIndex / 2;
if (parentIndex > 0 && HasHigherPriority(node.QueueIndex, parentIndex))
{
cascadeUp(ref node);
}
else
{
cascadeDown(ref node);
}
}
public PriorityQueueNode <T> Enqueue(T value, double priority)
{
CheckQueue();
numberOfNodes++;
if (numberOfNodes >= nodes.Length)
{
Resize(nodes.Length + (int)(0.1 * nodes.Length));
}
var node = new PriorityQueueNode <T>(value, priority, numberOfNodes, counter++);
nodes[numberOfNodes] = node;
cascadeUp(ref nodes[numberOfNodes]);
CheckQueue();
return(node);
}
private void cascadeDown(ref PriorityQueueNode <T> node)
{
// aka Heapify-down
int newParent;
int finalQueueIndex = node.QueueIndex;
while (true)
{
newParent = nodes[finalQueueIndex].QueueIndex;
int childLeftIndex = 2 * finalQueueIndex;
// Check if the left-child is higher-priority than the current node
if (childLeftIndex > numberOfNodes)
{
break;
}
if (HasHigherPriority(childLeftIndex, newParent))
{
newParent = childLeftIndex;
}
// Check if the right-child is higher-priority than either the current node or the left child
int childRightIndex = childLeftIndex + 1;
if (childRightIndex <= numberOfNodes)
{
if (HasHigherPriority(childRightIndex, newParent))
{
newParent = childRightIndex;
}
}
// If either of the children has higher (smaller) priority, swap and continue cascading
if (newParent != finalQueueIndex)
{
swap(finalQueueIndex, newParent);
finalQueueIndex = newParent;
}
else
{
break;
}
}
}
private void cascadeUp(ref PriorityQueueNode <T> node)
{
// aka Heapify-up
int current = node.QueueIndex;
int parent = node.QueueIndex / 2;
while (parent >= 1)
{
if (HasHigherPriority(parent, current))
{
break;
}
// Node has lower priority value, so move it up the heap
swap(current, parent);
current = nodes[parent].QueueIndex;
parent = current / 2;
}
}
/// <summary>
/// Resize the queue so it can accept more nodes. All currently enqueued nodes are kept.
/// Attempting to decrease the queue size to a size too small to hold the existing nodes
/// results in undefined behavior. This is an O(n) operation.
/// </summary>
///
public void Resize(int capacity)
{
#if DEBUG
if (capacity <= 0)
{
throw new InvalidOperationException("Queue size cannot be smaller than 1");
}
if (capacity < numberOfNodes)
{
throw new InvalidOperationException("Called Resize(" + capacity + "), but current queue contains " + numberOfNodes + " nodes");
}
#endif
var newArray = new PriorityQueueNode <T> [capacity + 1];
int highestIndexToCopy = Math.Min(capacity, numberOfNodes);
for (int i = 1; i <= highestIndexToCopy; i++)
{
newArray[i] = nodes[i];
}
nodes = newArray;
}
/// <summary>
/// Indicates whether the current object is equal to another object of the same type.
/// </summary>
/// <param name="other">An object to compare with this object.</param>
/// <returns>
/// true if the current object is equal to the <paramref name="other" /> parameter; otherwise, false.
/// </returns>
public bool Equals(PriorityQueueNode <T> other)
{
return(Value.Equals(other.value));
}
