# Prolog-Powered Sudoku Solving: Step-by-Step Guide for Homework Success

July 27, 2023
Ahmed Hassan
UAE
Prolog
Ahmed Hassan is a proficient Prolog Homework Help Expert with 12 years of knowledge. He completed his Master's degree from the University of Sharjah, UAE.

## Understanding Sudoku Puzzles

Let's make sure that we have a firm grasp of Sudoku puzzles before we delve into the world of Prologue. Nine 3x3 subgrades make up the 9x9 grid of a typical Sudoku puzzle. The goal is to fill in the empty cells with numbers between 1 and 9,

• Each row must contain all digits from 1 to 9 without repetition.
• Each column must contain all digits from 1 to 9 without repetition.
• Each 3x3 sub grid must contain all digits from 1 to 9 without repetition.

Sudoku is a brain-teasing puzzle that necessitates logical reasoning, deduction, and patience. Its straightforward rules give rise to countless combinations and possibilities. In addition to being a satisfying challenge, solving Sudoku puzzles helps to improve our cognitive function and problem-solving abilities. Sudoku is an intriguing option for those stepping into the world of programming because of its grid-based design, which is similar to the logical structure of programming. With this basic comprehension of Sudoku puzzles in hand, we can now investigate how Prolog's strong logic capabilities can assist us in overcoming these baffling mysteries piece by piece, revealing the techniques used to solve Sudoku puzzles with programming prowess.

## Setting Up Prolog Environment

You must first set up your programming environment before you can begin solving Sudoku puzzles in Prologue. Since Prologue is a logic programming language, it offers a distinctive method for solving issues, making it a great choice for solving Sudoku puzzles. You must first install Prologue on your system before you can proceed. Download the installer for your operating system from the official website of your preferred Prologue implementation, such as SWI-Prolog or GNU Prologue. For a successful environment set up, adhere to the installation guidelines given by the Prologue community. You'll be prepared to begin your journey of using Prologue to solve Sudoku puzzles once you have this potent language installed. As you delve further into the world of Sudoku, the intuitive and declarative nature of Prologue will allow you to explore logical solutions and improve your programming abilities.

### Installing Prolog

Installing the Prologue programming environment on your system is required before you start your journey of using Prologue to solve Sudoku puzzles. Visit the official website of your preferred Prologue implementation, such as SWI-Prolog or GNU Prologue, to complete this process. Once there, look for the installer that matches your operating system and start the download. To ensure a smooth setup and access to all of Prolog's functionality for solving Sudoku puzzles, follow the installation instructions given by the Prologue community.

### Understanding Prolog Terminology

It is important to understand some basic Prologue terms before learning more about how Prologue can be used to solve Sudoku puzzles.

The following terms lay the foundation for using the language correctly:

• Facts: In the Prologue programming language, facts are declarative statements that give details about the working domain. When referring to Sudoku, facts could be the initial numbers provided in the puzzle, serving as the basis for subsequent logical deductions.
• Rules: Prologue rules specify how various facts relate to one another, allowing the Prologue interpreter to infer new information from the facts already known. Prolog's logical reasoning and problem-solving abilities for Sudoku puzzles are greatly influenced by rules.
• Queries: In Prologue, queries are used to ask questions about the established facts and rules. You instruct the Prologue interpreter to look for solutions that meet the specified constraints by formulating queries. Through the use of Prolog's strong logic capabilities, this querying procedure is essential for discovering correct Sudoku solutions.

## Representing Sudoku Puzzles in Prolog

We must implement the Sudoku rules and represent the puzzle in order to solve Sudoku puzzles in Prologue. We can represent the Sudoku grid, where each cell can either hold a number from 1 to 9 or remain unbound, representing an empty cell, using a list of lists thanks to Prolog's adaptability. We can successfully use Prolog's logic programming capabilities to address Sudoku's complexity and methodically deduce valid solutions by structuring the puzzle in this way. The power of Prolog's declarative paradigm allows us to solve the puzzle of how to solve Sudoku puzzles by facilitating the exploration of various combinations and constraints.

### Initializing the Sudoku Grid

Let's start by initializing the Sudoku grid with the given puzzle. We'll use numbers from 1 to 9 to represent the initial known values and use variables for the empty cells.

% Sample Sudoku puzzle

```sudokuPuzzle([     [5, 3, _, _, 7, _, _, _, _],     [6, _, _, 1, 9, 5, _, _, _],     [_, 9, 8, _, _, _, _, 6, _],     [8, _, _, _, 6, _, _, _, 3],     [4, _, _, 8, _, 3, _, _, 1],     [7, _, _, _, 2, _, _, _, 6],     [_, 6, _, _, _, _, 2, 8, _],     [_, _, _, 4, 1, 9, _, _, 5],     [_, _, _, _, 8, _, _, 7, 9] ]). ```

### Implementing Sudoku Rules

Next, we need to implement the rules of Sudoku in Prolog. These rules will ensure that each row, column, and 3x3 subgrid contains all digits from 1 to 9 without repetition.

% Rule: All elements in the list must be distinct

```distinct([]). distinct([H | T]) :- not(member(H, T)), distinct(T). ```

% Rule: Transpose a matrix

```transpose([], []). transpose([[] | _], []). transpose([[H | T] | Rows], [Col | RestCols]) :-     firstColumn([[H | T] | Rows], Col, [T | RestRows]),     transpose([T | RestRows], RestCols). ```

% Rule: Extract the first column from the matrix

```firstColumn([], [], []). firstColumn([[H | T] | Rows], [H | HRest], [T | TRest]) :- firstColumn(Rows, HRest, TRest). ```

% Rule: A 3x3 subgrid must contain all digits from 1 to 9 without repetition

```validSubgrid(Grid) :-     transpose(Grid, Columns),     validRows(Grid),     validRows(Columns),     validateSubgridCells(Grid). ```

% Rule: Each row of the Sudoku grid must contain all digits from 1 to 9 without repetition

```validRows([]). validRows([Row | Rest]) :- distinct(Row), validRows(Rest). ```

% Rule: Validate each 3x3 sub grid of the Sudoku grid

```validateSubgridCells([]). validateSubgridCells([Row1, Row2, Row3 | RestRows]) :-     firstColumn(Row1, C1, R1), firstColumn(Row2, C2, R2), firstColumn(Row3, C3, R3),     distinct(C1), distinct(C2), distinct(C3),     validateSubgridCells([R1, R2, R3 | RestRows]). ```

### Solving the Sudoku Puzzle

Now that we have represented the puzzle and implemented the rules, we can proceed to solve the Sudoku puzzle using Prolog. We'll use backtracking and recursion to find the solution.

% Rule: Solving the Sudoku puzzle

```solveSudoku(Puzzle, Solution) :-     Puzzle = Solution,     validSubgrid(Solution). ```

## Putting It All Together

Now that everything is in place, we can use Prologue to solve Sudoku puzzles. We can quickly look for answers to even the most difficult puzzles by combining the initialized Sudoku grid, the application of Sudoku rules, and Prolog's backtracking and recursive capabilities. A powerful tool for tackling challenging puzzles like Sudoku, Prolog's declarative approach enables us to represent the problem logically and systematically explore potential solutions. We can use logic programming to navigate the complexities of Sudoku through the integration of puzzle representation and Prolog's solving techniques, giving us a complete manual to conquer these alluring number-placement puzzles. Here is a list of each step:

### Set Up Prolog Environment

Installing Prologue on your computer is the first step in using it to start solving Sudoku puzzles. Download the installer for your operating system from the official website of your preferred Prologue implementation, such as SWI-Prolog or GNU Prologue. For a successful environment set up, adhere to the installation guidelines given by the Prologue community. Understanding the fundamental terms used in Prologue, such as facts, rules, and queries, is crucial after Prologue has been installed. You can use Prolog's strong logic capabilities to explore the world of Sudoku problem-solving by becoming familiar with these fundamental ideas.

### Represent the Sudoku Puzzle

The given Sudoku puzzle needs to be represented in the programming environment once Prologue is ready to use. The Sudoku grid will be organized using a list of lists, with each cell able to either hold a number from 1 to 9 or remain unbound, denoting an empty cell. By using this representation to initialize the puzzle, we build a logical framework that Prologue can use to investigate and systematically arrive at solutions. With this methodical approach, we can effectively use Prolog's backtracking and recursive techniques to navigate the complex possibilities of the Sudoku puzzle and eventually find the elusive solutions.

### Implement Sudoku Rules

The implementation of the guidelines governing Sudoku's validity follows the representation of the Sudoku puzzle in the Prologue as the next crucial step. These guidelines make sure that every row, column, and 3x3 sub grid abides by the basic Sudoku requirements, which require that all digits from 1 to 9 appear once only. We create a logical framework for the program to verify potential solutions and toss out unworkable combinations by defining these rules in Prologue. The application of these guidelines forms the basis of the Sudoku-solving procedure, allowing Prologue to logically investigate the puzzle's possibilities and gradually infer the right digit placements.

### Solve the Puzzle

It's time to use Prolog's backtracking and recursive features after laying the foundation with the puzzle representation and rule implementation. As it moves through the Sudoku grid, Prologue backtracks systematically to investigate different avenues and potential answers, constantly reevaluating options and tossing out bad ones. Prologue can effectively handle each subproblem within the 3x3 subgrades thanks to its recursive nature, iterating through various digit combinations and exhaustively looking for workable solutions. Prologue gradually solves each Sudoku puzzle's mystery by utilizing the power of backtracking and recursion, finding the right combination of numbers in the end, and successfully completing the challenge.

## Conclusion

In conclusion, using Prologue to solve Sudoku puzzles is a rewarding and instructive experience. The declarative nature of Prologue makes it the perfect language for Sudoku fans and programming students alike because it allows us to solve logic-based problems. We can solve challenging Sudoku puzzles using Prologue by understanding its rules and applying them methodically, which also improves our programming skills. Adopting Prologue as a tool for problem-solving creates new opportunities for developing analytical and logical thinking skills. Successfully solving Sudoku puzzles in Prologue provides a sense of accomplishment that motivates learners to keep learning and piques their interest in taking on new challenges in the field of logic programming. Therefore, the next time a Sudoku puzzle calls, why not start the Prologue journey and open the door to your academic success, where both intellectual satisfaction and programming successes wait?