Priority queue classes with priority update

A limitation in the design of the interface of C++ standard priority queues is addressed. The use of priority queues in Dijkstra’s shortest path search algorithm is used as an example. Priority queues are often implemented using heaps. There is a problem, as it may be necessary to change the priority of an element while it is in the queue, but finding the element from within a heap is costly. The problem may be solved by keeping track, in a variable that is outside the heap, of the position of the element in the heap. Unfortunately, this is impossible with the template class interface used by the C++ standard library priority queue. In this research, the problem is analysed in detail. Four interface designs and corresponding implementations are suggested. They are compared experimentally to each other and the C++ design.