Version 5.0 The LEDA User Manual

11.21 Bounded Node Priority Queues ( b node pq )
1. Definition
An instance of the data type b node pq is a priority queue of nodes with integer
priorities with the restriction that the size of the minimal interval containing all priorities
in the queue is bounded by N, the minimum priority is never decreasing, and every node is
contained in at most one queue. When applied to the empty queue the del min - operation
returns a special default minimum node defined in the constructor of the queue.
#include < LEDA/graph/b node pq.h >
2. Creation
b node pq PQ;
introduces a variable PQ of type b node pq and initializes it
with the empty queue with default minimum node nil.
b node pq PQ(node v);
3. Operations
introduces a variable PQ of type b node pq and initializes it
with the empty queue with default minimum node v.
node PQ.del min( ) removes the node with minimal priority from PQ and
returns it (the default minimum node if PQ is empty).
void PQ.insert(node w, int p) adds node w with priority p to PQ.
void PQ.del(node w, int = 0) deletes node w from PQ.
4. Implementation
Bounded node priority queues are implemented by cyclic arrays of doubly linked node
lists.
5. Example
Using a b node pq in Dijktra’s shortest paths algorithm.
int dijkstra(const GRAPH& g, node s, node t)
{ node_array dist(g,MAXINT);
b_node_pq PQ(t); // on empty queue del_min returns t
dist[s] = 0;
for (node v = s; v != t; v = PQ.del_min() )