Re: priority_queue cannot update element value

From:

Barry <dhb2000@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Thu, 10 Apr 2008 08:37:49 -0700 (PDT)

Message-ID:

<601397c1-8573-4a0f-98dd-d45e1c35d0c8@w4g2000prd.googlegroups.com>

On Apr 10, 7:58 pm, thomas <FreshTho...@gmail.com> wrote:

I want to use a priority_queue like STL data structure.
But I found that priority_queue cannot update element value: only pop/
push is supported.

I'm using priority_queue to implement the prim MST algorithm.
So I need the priority_queue to contain the key[] values for each
vertex not included in the final tree. Of course the pop and push
operation is what I need, but I also need to update the weight value.

Can I use priority_queue to make it work?
Or any other way to use existing STL containers to implement the prim
MST algorithm?

I think that's what PQ is designed for.
If you want to use PQ-like container with your requirement,
you can see how PQ is defined in your compiler library implementation,
I think it's easy for you to rewrite a new container with the STL
heap algorithms, while you can supply iterator support for your
container.

Yet another *quick and dirty* way is to inherit PQ as base class, and
add accessor to
the underlying "protected" sequence named 'c'. But keep in mind that
inheriting
from a STL container is not a good design.