keyur-dasarwar / 8puzzlegamesovler

Using python to solve the eight puzzle game antomatically

8PuzzleGameSovler

Using python to solve the eight puzzle game antomatically!

Introduction

8-Puzzle is a square board with 9 tiles. There are 8 of them have number on it which is through 1-8 and also a blank tile. The player can swap the blank tile with its adjacent (horizontally and vertically) tile each time.

The objective in the game is to begin with an arbitrary configuration of tiles, and move them to get the target configuration of tiles as shown in the above figure.

Environment

Language: Python2.7

Modules: math / time / random

Design Pattern: strategy design pattern

Implementation

8-Puzzle problem is actually a state space search which means to find a path from inital state to goal state.

In this python program, I implemented the following search algorithms:

• Breadth First Search (BFS)
• Descent Hill Climbing
• A*

For Descent Hill Climbing and A* algorithm, I inplement the following heuristic functions:

• H1( ): Counting Out Of Placed Tiles
• H2( ): Manhattan Distance Of Tiles Out Of Place
• H3( ): Manhattan Distance + 2 * Number Of Linear Conflict

The final report will give you a comparision between each algorithm based on different heuristic functions, which includes:

• Algorithm Name
• Heuristic Function
• Elapsed Time
• Number of Steps
• Solution Path

Usage

step 1

Open the input.txt, and type in the initial state. e.g. 3 2 4 1 5 6 x 7 9 8

x represent the blank tile

step 2

Open the termianl, type in python main.py.

step 3

Open the output.txt, you can get the final report.

Algorithm: A*
Heuristic function: H1()     (Counting Out Of Placed Tiles)
Elapsed time: 0.000249862670898 s
Number of steps required: 4

123      123      123      123      123      
746  =>   46  =>  4 6  =>  456  =>  456 
 58      758      758      7 8      78