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astar-algorithm-cpp

Summary

This code is an efficient implementation in C++ of the A* algorithm. It accompanies the A* tutorial on this site: http://www.heyes-jones.com/astar.html

The code has been used in several popular video games including THQ's "Company of Heroes", Activision's "Gun" as well as in the popular game prototyping engine Angel. http://code.google.com/p/angel-engine/

It has also used in many University assignments and projects.

License

This software is released under the MIT License, see license.txt

Commercial Use

This software has been used in several widely distributed video games, as well as industrial and academic projects. Should you decide to ship this code in a commercial product, or wish to show your appreciation, I ask that you contact me just to let me know. I would also greatly appreciate it if you could contribute to Unicef, a charity which helps children worldwide. http://www.unicef.org/

If you wish to be added to the list of known products using the code please contact me.

Using this code:

Installing

Build in place using:

g++ findpath.cpp -o findpath

g++ 8puzzle.cpp -o 8puzzle

Introduction

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 3.4.4

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 3rd August 2006

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

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

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

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.

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Implementation of the A* algorithm in C++

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