# Write a Program to Solve Sliding Block 8 Puzzle using Lisp

Delve into our innovative approach to mastering the classic Sliding Block 8 Puzzle using the Lisp programming language. This captivating puzzle dares you to elegantly arrange the numbers from 1 to 8 on a 3x3 grid, an intriguing challenge that has captivated minds for generations. In this comprehensive guide, we take you on a journey through our carefully crafted implementation of a fundamental puzzle solver using Lisp.

## Lisp Puzzle Algorithm: Efficient 8-Puzzle Solution

Explore our comprehensive guide on solving the Sliding Block 8 Puzzle using Lisp. Delve into our approach, solver, and optimization strategies to unravel the intricacies of puzzle-solving. Whether you're a programming enthusiast or seeking help with your Lisp assignment, this resource equips you with the tools to master the challenge.

### Puzzle State Representation

In this approach, the initial and goal states of the puzzle are defined. The initial state captures the puzzle's starting arrangement, while the goal state defines the desired configuration. Here's how these states are defined:

``` ```lisp (defvar *goal-state* '(1 2 3 4 5 6 7 8 0)) (defvar *initial-state* '(2 8 3 1 6 4 7 0 5)) ``` ```

Puzzle Manipulation Functions

To manipulate the puzzle effectively, a set of functions has been crafted:

• `find-position`: This function helps locate a specific element within the puzzle state.
• `swap-elements`: Swapping elements is essential for rearranging the puzzle state.
• `get-possible-moves`: A function to determine allowable moves based on the position of the empty space.
• `apply-move`: This function applies a move by exchanging the empty space with an adjacent tile.

Goal Test

The goal is to determine whether a given puzzle state matches the predefined goal state. This is achieved using the `goal-test` function:

``` ```lisp (defun goal-test (state) (equal state *goal-state*)) ``` ```

Depth-First Search Algorithm

The primary solving algorithm is the Depth-First Search (DFS). It explores possible moves and states through recursive iterations, effectively avoiding loops and backtracking as required. Here's how the `dfs` function operates:

``` ```lisp (defun dfs (node visited) (cond ((goal-test node) (reverse visited)) ((member node visited) nil) (t (dolist (move (get-possible-moves (find-position 0 node))) (let ((new-state (apply-move node move)) (result (dfs new-state (cons node visited)))) (if result (return result)))))) (defun solve-puzzle () (dfs *initial-state* '())) ``` ```

Bringing it All Together

To unravel the puzzle's mystery, engage the `solve-puzzle` function. This function activates the DFS algorithm and presents the solution path:

``` ```lisp (format t "Solution path: ~a~%" (solve-puzzle)) ``` ```

## Conclusion

In conclusion, armed with this foundational Lisp program, you now possess a fundamental tool for tackling the intricacies of the Sliding Block 8 Puzzle. However, remember that this marks just the beginning of your journey. Delve deeper to unearth a realm of advanced algorithms and refined optimizations, inviting you to fortify both performance and capabilities. As you build upon this base, you'll cultivate a landscape of creative problem-solving, shaping your prowess in puzzle-solving and Lisp programming alike. Approach challenges with curiosity, embracing each as an opportunity to expand your horizons. The Sliding Block 8 Puzzle serves as a stepping stone in the grand narrative of exploration, where every line of code penned is a gateway to enlightenment. With this guide, we hope to illuminate the boundless potential lying within Lisp programming and puzzle-solving, ushering you toward a future brimming with coding triumphs.