public TPriority FrontPriority()
{
// assumes pq is not empty; up to calling code
StablePriorityQueueItem <TPriority, TValue> frontItem = this.data[0]; // fetch the front
return(frontItem.Priority);
}
private void DeleteAt(int index)
{
int lastIndex = this.data.Count - 1; // last index (before removal)
this.data[index] = this.data[lastIndex];
this.data.RemoveAt(lastIndex);
lastIndex--; // last index (after removal)
int parent = index; // parent index. start at front of pq
while (true)
{
int child = (parent * 2) + 1; // left child index of parent
if (child > lastIndex)
{
break; // no children so done
}
int rc = child + 1; // right child
if (rc <= lastIndex && !this.IsLarger(rc, child)) // if there is a rc (ci + 1), and it is smaller than left child, use the rc instead
{
child = rc;
}
if (!this.IsLarger(parent, child))
{
break; // parent is smaller than (or equal to) smallest child so done
}
StablePriorityQueueItem <TPriority, TValue> tmp = this.data[parent];
this.data[parent] = this.data[child];
this.data[child] = tmp; // swap parent and child
parent = child;
}
}
public TValue Dequeue()
{
// assumes pq is not empty; up to calling code
StablePriorityQueueItem <TPriority, TValue> frontItem = this.data[0]; // fetch the front
this.DeleteAt(0);
return(frontItem.Value);
}
public void Enqueue(TPriority priority, TValue item)
{
this.data.Add(new StablePriorityQueueItem <TPriority, TValue>(priority, this.insertions, item));
this.insertions++;
int child = this.data.Count - 1; // child index; start at end
while (child > 0)
{
int parent = (child - 1) / 2; // parent index
if (this.IsLarger(child, parent))
{
break; // child item is larger than (or equal) parent so we're done
}
StablePriorityQueueItem <TPriority, TValue> tmp = this.data[child];
this.data[child] = this.data[parent];
this.data[parent] = tmp;
child = parent;
}
}
public void AddOrSetPriority(TPriority priority, TValue item)
{
bool isInQueue = false;
// search for item
for (int ii = 0; ii < this.data.Count; ii++)
{
if (this.data[ii].Value.Equals(item))
{
// if item is found, delete it
isInQueue = true;
this.DeleteAt(ii);
break;
}
}
// re-add item
if (!isInQueue)
{
this.insertions++;
}
this.data.Add(new StablePriorityQueueItem <TPriority, TValue>(priority, this.insertions, item));
int child = this.data.Count - 1; // child index; start at end
while (child > 0)
{
int parent = (child - 1) / 2; // parent index
if (this.IsLarger(child, parent))
{
break; // child item is larger than (or equal) parent so we're done
}
StablePriorityQueueItem <TPriority, TValue> tmp = this.data[child];
this.data[child] = this.data[parent];
this.data[parent] = tmp;
child = parent;
}
}
