data structure: implement pairing heap without use of shared_ptr

[jere8184]

Continuation of #1707 which was accidentally closed when I deleted my fork of openage

[heinezen]

The sanity checks are not running through and you need to rebase again please.

[heinezen]

Ah I didn't thought of that we have top do this for the deletion.

It's probably not a good idea to change the function like this because it effectively reverses the order of walking the tree (root will now be the last node that func is applied to). I guess the best solution then is to leave this function as-is and not use iter_all.

Instead, you can use the code you have written here in clear() but replace func(root) with delete root

[jere8184]

How about adding a reverse argument to walk tree? (see changes)

[heinezen]

Yes, I think that is also a nice option.

I pushed a commit to your branch that additionally makes the reversing a compile-time option, making it faster to execute.

[heinezen]

Looks like the amount of calls in the portal_a_star function almost halfed. Doesn't make it twice as fast, but it's a good progress. The event queue should also benefit from this change.

[heinezen]

I'm going to merge. Well done!