public PQKey Enqueue(T item, double priority)
{
PQWrapper <T> newItem = new PQWrapper <T>();
newItem.key = new PQKey();
newItem.data = item;
newItem.priority = priority;
list.Add(newItem);
int ci = list.Count - 1; // child index; start at end
newItem.key.loc = ci;
while (ci > 0)
{
int pi = (ci - 1) / 2; // parent index
if (list[ci].CompareTo(list[pi]) >= 0)
{
break; // child item is larger than (or equal) parent so we're done
}
PQWrapper <T> tmp = list[ci];
list[ci] = list[pi];
list[pi] = tmp;
list[ci].key.loc = ci;
list[pi].key.loc = pi;
ci = pi;
}
return(newItem.key);
}
public void ChangePriority(PQKey key, double newP)
{
double oldP = list[key.loc].priority;
list[key.loc].priority = newP;
if (oldP > list[key.loc].priority)
{
int ci = key.loc;
while (ci > 0)
{
int pi = (ci - 1) / 2; // parent index
if (list[ci].CompareTo(list[pi]) >= 0)
{
break; // child item is larger than (or equal) parent so we're done
}
PQWrapper <T> tmp = list[ci]; list[ci] = list[pi]; list[pi] = tmp;
list[ci].key.loc = ci;
list[pi].key.loc = pi;
ci = pi;
}
}
else
{
int pi = key.loc; // parent index. start at front of pq
int li = list.Count - 1;
while (true)
{
int ci = pi * 2 + 1; // left child index of parent
if (ci > li)
{
break; // no children so done
}
int rc = ci + 1; // right child
if (rc <= li && list[rc].CompareTo(list[ci]) < 0) // if there is a rc (ci + 1), and it is smaller than left child, use the rc instead
{
ci = rc;
}
if (list[pi].CompareTo(list[ci]) <= 0)
{
break; // parent is smaller than (or equal to) smallest child so done
}
PQWrapper <T> tmp = list[pi]; list[pi] = list[ci]; list[ci] = tmp; // swap parent and child
//Adjust key vals
list[ci].key.loc = ci;
list[pi].key.loc = pi;
pi = ci;
}
}
}
public int CompareTo(PQWrapper <T> rhs)
{
if (this.priority < rhs.priority)
{
return(-1);
}
else if (this.priority > rhs.priority)
{
return(1);
}
else
{
return(0);
}
}
public T Dequeue()
{
// assumes pq is not empty; up to calling code
int li = list.Count - 1; // last index (before removal)
T frontItem = list[0].data; // fetch the front
list[0] = list[li];
list.RemoveAt(li);
--li; // last index (after removal)
//Adjust key vals
for (int i = 0; i < list.Count; ++i)
{
list[i].key.loc = i;
}
int pi = 0; // parent index. start at front of pq
while (true)
{
int ci = pi * 2 + 1; // left child index of parent
if (ci > li)
{
break; // no children so done
}
int rc = ci + 1; // right child
if (rc <= li && list[rc].CompareTo(list[ci]) < 0) // if there is a rc (ci + 1), and it is smaller than left child, use the rc instead
{
ci = rc;
}
if (list[pi].CompareTo(list[ci]) <= 0)
{
break; // parent is smaller than (or equal to) smallest child so done
}
PQWrapper <T> tmp = list[pi]; list[pi] = list[ci]; list[ci] = tmp; // swap parent and child
//Adjust key vals
list[ci].key.loc = ci;
list[pi].key.loc = pi;
pi = ci;
}
return(frontItem);
}
