Comments on: Heaps and Priority Queues in C++ – Part 1: Heaps Basics

By: Jean-Simon Lapointe

Jean-Simon Lapointe — Sun, 18 Mar 2018 19:43:00 +0000

In reply to Jonathan Boccara. I just checked, and it seems that the operator < is overloaded for std::set, and it is the std::lexicographical_compare. They thought of everything, we can't even invent an operator! :)

By: Jonathan Boccara

Jonathan Boccara — Sun, 18 Mar 2018 19:35:00 +0000

In reply to Jean-Simon Lapointe. You're right Jean-Simon, I've made the correction. Thanks for the feedback!

By: Jean-Simon Lapointe

Jean-Simon Lapointe — Sat, 17 Mar 2018 02:46:00 +0000

A heap of set could not be implemented with the relationship ‘is included in’, since this relation does not define a total order (only a partial order): i.e.: there exist two sets a and b such that neither is included in the other. For example the set containing {1,2} and the set containing {1,3}.
There exist some total order on sets, like lexicographical order, that would make a heap of set valid.
Thanks for the post, always great to read…

By: Jonathan Boccara

Jonathan Boccara — Fri, 16 Mar 2018 08:41:00 +0000

In reply to Mayank. Yes! I made the correction, thanks for this precision Mayank :)

By: Mayank

Mayank — Thu, 15 Mar 2018 21:42:00 +0000

Under “Checking for the heap property”, you wrote that “returns true if numbers is a heap and false otherwise”. I think this should rather be “returns true if numbers is a **max** heap and false otherwise”.

By: Jonathan Boccara

Jonathan Boccara — Wed, 14 Mar 2018 23:07:00 +0000

In reply to Aymen Schehaider. Yes Aymen, this would be a heap too. Heaps can have various forms depending on the order that their elements were inserted. The next post (on Friday) shows how elements get inserted into a heap, so we can talk more about this then if you like.

By: Tom

Tom — Wed, 14 Mar 2018 10:20:00 +0000

Important to note that the heap must satisfy the “shape property” of a binary heap for the heap to be able to be stored in an array without using children pointers. If each level of the heap is not fully-filled (except for the final row) then you can’t store the heap in an array unless you use child pointers between elements.

By: Aymen Schehaider

Aymen Schehaider — Tue, 13 Mar 2018 16:30:00 +0000

I did not get how the heap is created with that values ?

why couldn’t we had something like “9 8 7 6 5 …”

By: Jonathan Boccara

Jonathan Boccara — Tue, 13 Mar 2018 07:38:00 +0000

In reply to Oleg Bogdanov. Yes it's level order, this is fixed now, thanks for the feedback Oleg.

By: Oleg Bogdanov

Oleg Bogdanov — Tue, 13 Mar 2018 02:53:00 +0000

I dont think this is ‘inorder traversal’ to be honest