Comments on: Heaps and Priority Queues in C++ – Part 3: Queues and Priority Queues https://www.fluentcpp.com/2018/03/20/heaps-and-priority-queues-in-c-part-3-queues-and-priority-queues/ Jonathan Boccara's blog Fri, 01 Jun 2018 15:04:00 +0000 hourly 1 https://wordpress.org/?v=6.5.3 By: jft https://www.fluentcpp.com/2018/03/20/heaps-and-priority-queues-in-c-part-3-queues-and-priority-queues/#comment-1034 Fri, 01 Jun 2018 15:04:00 +0000 https://www.fluentcpp.com/?p=2904#comment-1034 Another way to implement a priority-queue is to use a multi-map. A map is always sorted by its key. So if the key is the priority (0 being highest, 999 the lowest etc) and the mapped-value is the associated data, then .begin() will always point to the highest priority (lowest key) (or one of the highest priority) and equal_range() returns iterators to all elements that have the same priority.

So to get the iterators to the current highest priority

auto priors = mymap.equal_range((mymap.begin())->first);

and to erase the elements with equal priority

mymap.erase(priors.first, priors.second);

New elements can be just inserted as multi-map properties mean that they are inserted in the right priority.

Unless you really need a heap-type tree structure to access other elements, we’ve found this way to be fairly simple and fast for large queues.

]]> By: Jonathan Boccara https://www.fluentcpp.com/2018/03/20/heaps-and-priority-queues-in-c-part-3-queues-and-priority-queues/#comment-888 Tue, 27 Mar 2018 07:01:00 +0000 https://www.fluentcpp.com/?p=2904#comment-888 In reply to Andrew Starikov.

Absolutely, I’ve added them now, thanks!

]]> By: Andrew Starikov https://www.fluentcpp.com/2018/03/20/heaps-and-priority-queues-in-c-part-3-queues-and-priority-queues/#comment-886 Mon, 26 Mar 2018 14:40:00 +0000 https://www.fluentcpp.com/?p=2904#comment-886 No links in the beginning (series) and end (related) of the post

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