sudoku

I'm writing an algorithm in PHP to solve a given Sudoku puzzle. I've set up a somewhat object-oriented implementation with two classes: a Square class for each individual tile on the 9x9 board, and a Sudoku class, which has a matrix of Square s to represent the board. The implementation of the algorithm I'm using is a sort of triple-tier approach. The first step, which will solve only the most basic puzzles (but is the most efficient), is to fill in any squares which can only take a single value based on the board's initial setup, and to adjust the constraints accordingly on the rest of the

I have been working on a sudoku puzzle generator in java, I wrote this class to generate the puzzle but it is not correctly generating the puzzle. Here is an example of what I am getting: As you can see this is not a valid sudoku solution. But looking at my code, I don't understand why it is not generating a valid puzzle. Can someone explain why this does not work correctly? package sudoku; import java.util.Random; public class Puzzle { // number generator Random gen = new Random(); // 9x9 puzzle int puzzle[][] = new int[9][9]; public int[][] generate() { // add each number to the board for

Can someone please help me understand this solution : Initialize 2D array with 81 empty grids (nx = 9, ny = 9) Fill in some empty grid with the known values Make an original copy of the array Start from top left grid (nx = 0, ny = 0), check if grid is empty if (grid is empty) { assign the empty grid with values (i) if (no numbers exists in same rows & same columns same as (i) & 3x3 zone (i) is currently in) fill in the number if (numbers exists in same rows & same columns same as (i) & 3x3 zone (i) is currently in) discard (i) and repick other values (i++) } else { while (nx < 9) { Proceed to

I'm working through 'Seven Languages in Seven Weeks', and I'm just trying to get an example from the book working. It solves a mini sudoku grid (4x4). The author is using gprolog, but I am using swi-prolog (I couldn't get gprolog to work on my VM for whatever reason, but swi-prolog worked first try). I am running Ubuntu 10.04 in VirtualBox 4.0.4 r70112 (hopefully that's not too relevant!) Here is the code in my prolog file: :- use_module(library(clpfd)). valid([]). valid([Head|Tail]) :- all_different(Head), % in the book, this is 'fd_all_different' valid(Tail). % beginning of sudoku rule