Overview
15 puzzle is a game which consists of a frame of numbered square tiles in random order with one tile missing. The goal is to rearrange the blocks so that they are in order, using as few moves as possible.
Implementation
It is implemented as a best-first search. The solution to the problem illustrates a general artificial intelligence methodology known as the A search algorithm*. A seach node of the game is represented by the combination of a board, the number of moves made to reach the board and the previous search node. First, the initial search node (initial board) is inserted into a priority queue. Then, the search node with the minimum priority is deleted from the priority queue and all its neighboring search nodes are inserted. This procedure is repeated until the goal board is dequeued from the priority queue. The success of this approach hinges on the choice of priority function for a search node. We consider two priority functions:
- Hamming priority function. The number of blocks in the wrong position, plus the number of moves made so far to get to the search node.
- Manhattan priority function. The sum of the Manhattan distances (sum of the vertical and horizontal distance) from the blocks to their goal positions, plus the number of moves made so far to get to the search node.
Development
Create a build directory, let's say you create it within this repository's root (which is not recommended, btw, but just for the seek of example):
mkdir 15-puzzle_buildEnter the newly created build directory and run cmake. To also create the
test executables, pass the -DBUILD_TESTS=true flag to cmake.
cd 15-puzzle_build
cmake ..Note: Make sure you have installed at least the 2.8 cmake version.
Then just simply run make and make install and the project should be
completely built.
Footnote
Don't message me that this small project is overly-structured. That's the whole point - to exercise working with the tools which are used in big projects.