GDevelop/Extensions/AStarAutomatism

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A* Algorithm by Justin Heyes-Jones

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Description

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This implementation is intended to be simple to read yet fairly

efficient. To build it you can compile, with any recent C++ compiler,

the following files :



For 8-puzzle solver



	8puzzle.cpp

	stlastar.h

	optionally fsa.h



Command line 



	8puzzle with no arguments runs with one of the boards in the cpp file, you can

	select the one you want changing the conditional compiliation instructions. Or if you

	prefer pass in a board on the command line using digits for the tile positions, where

	zero is the space. The board runs from left to right, each row at a time:

	

		8puzzle 013824765



For path finder 



	findpath.cpp

	stlastar.h

	optionally fsa.h



	pathfind has no arguments. You can edit the simple map in pathfind.cpp and the start 

	and goal co-ordinates to experiement with the pathfinder.



Fixed size allocator notes: As mentioned briefly in the tutorial you can enable and disable the

faster memory allocation. This allocates a fixed size block of memory, so you have to specify this size

with the astar constructor. You need to enlarge it if you hit an out of memory assert during the

search.



Compilation notes:



Microsoft Visual C++ : Confirmed working with version 8.0.50727 with some deprecation warnings

I'm going to leave the deprecation warnings in so that it still works cleanly with GCC. 

TODO Make a non-deprecated compliant version using compiler checking



GCC notes : Compiled using version 3.4.5 (MingW)



Please let me know if it doesn't work for you and I will try to help. I cannot help if you are using

an old compiler such as Turbo C++, since I update the code to meet Ansi Standard C++ as required.



At least in as far as the Microsoft and GCC compilers adhere to Ansi and add breaking changes.



History:



Updated 1th February 2009

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Fixed Manhattan distance bug. Should use absolute values.



Got rid of sprintfs, use cout instead.



Updated 3rd August 2006

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Fixed memory leak

Fixed special case handling for finding better path to a closed node

Fixed bug with comparing the start node with a new node by pointer instead of value

Changed code to use Manhattan distance heuristic with pathfind.cpp as it is more correct





Updated 27th September 2005

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Thanks to Gyan singh for pointing out the code no longer compiles under GCC.



Well, that was the case. I've removed a Gnu offending conio.h include, and added lots more typename

keywords, which seem to be required now when making an iterator using a template type.



If anyone knows what the breaking change to the compiler was for, let me know.



Updated 6th September 2005

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	Finally set the path to fsa.h correctly, sorry about that.

	8puzzle.cpp now defaults to using a demo puzzle that solves in a short time.

	Added typename keyword to comply with latest ISO standards. 



Updated November 26th 2001

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	Fixed a bug. When a node is deleted from the Open list I did sort_heap when make_heap

	is needed to keep the heap structure valid. This causes the search to go awry under some

	conditions. Thanks to Mike Ryynanen for tracking this down.



justinhj@hotmail.com



http://www.geocities.com/jheyesjones/astar.html



or



http://www.heyes-jones.com/astar.html



A* Algorithm Implementation using STL is

Copyright (C)2001-2005 Justin Heyes-Jones



Permission is given by the author to freely redistribute and 

include this code in any program as long as this credit is 

given where due.

 

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