Version 5.0 The LEDA User Manual

8.2 Bounded Priority Queues ( b priority queue )
1. Definition
An instance Q of the parameterized data type b priority queue is a collection of items
(type b pq item). Every item contains a priority from a fixed interval [a..b] of integers
(type int) and an information from an arbitrary type I. The number of items in Q is
called the size of Q. If Q has size zero it is called the empty priority queue. We use 〈p, i〉
to denote a b pq item with priority p ∈ [a..b] and information i.
Remark: Iteration over the elements of Q using iteration macros such as forall is not
supported.
#include < LEDA/core/b prio.h >
2. Creation
b priority queue Q(int a, int b);
creates an instance Q of type b priority queue with key type
[a..b] and initializes it with the empty priority queue.
3. Operations
b pq item Q.insert(int key, const I& inf )
adds a new item < key, inf > to Q and returns it.
Precondition: key ∈ [a..b]
void
Q.decrease key(b pq item it, int newkey)
makes newkey the new priority of item it.
Precondition: it is an item in Q, newkey ∈ [a..b]
and newkey is not larger than prio(it).
void Q.del item(b pq item x) deletes item it from Q.
Precondition: it is an item in Q.
int Q.prio(b pq item x) returns the priority of item i.
Precondition: it is an item in Q.
const I& Q.inf(b pq item x) returns the information of item i.
Precondition: it is an item in Q.
b pq item Q.find min( ) returns an item with minimal priority (nil if Q is
empty).
I Q.del min( ) deletes the item it = Q.find min( ) from Q and
returns the information of it.
Precondition: Q is not empty.
void Q.clear( ) makes Q the empty bounded prioriy queue.