Sudoku
Thursday, February 15th, 2007
So the sudoku craze has swept the world. “Everyone” has built sudoku solvers, but where are the generators. This function does just that! It allows you to generate random “solved” sudoku and the associated puzzle. It produces two strings $solution and $puzzle which can be exploded into arrays.
/**
* Method to add puzzle
* puzzle generated using the “Peraita method - Author unknown”
* @param string $difficulty The difficulty raing of the puzzle (used to remove numbers)
* $size the base size of the grid eg. 3 = 9×9 board, 5 = 25*25 board
**/
function generate($difficulty)
{
// set up board size
if($difficulty != 4){
$size = 3;
}else{
$size = 5;
}
// randomize numbers
$numbers = range(1, pow($size, 2));
shuffle($numbers);
// row index sets
$x = 1;
for($i = 1; $i <= pow($size, 2); $i++){
$a = “rowIndex_” . $i; //set up variable names eg $rowIndex_1
for($ii = 1; $ii <= pow($size, 2); $ii++){
${$a}[$ii] = $x; //set up variable eg $rowIndex[0] = 1
$x = $x + 1;
}
$allRows[$i] = $$a; //set up array eg $temp[0] = $rowIndex_1
}
$temp = array_chunk($allRows, $size, true);
foreach($temp as $key => $arrRow){
$a = “arrRow_” . $key; // set up variable names
$$a = $arrRow; // set up variable
$arrAllRows[$key] = $$a; // set up array
}
// column index sets
for($i = 1; $i <= pow($size, 2); $i++){
$a = “colIndex_” . $i; // set up variable names
$x = $i;
for($ii = 1; $ii <= pow($size, 2); $ii++){
${$a}[$ii] = $x; // set up variable
$x = $x + pow($size, 2);
}
$allCols[$i] = $$a; // set up array
}
$temp = array_chunk($allCols, $size, true);
foreach($temp as $key => $arrCol){
$a = “arrCol_” . $key; // set up variable names
$$a = $arrCol; // set up variable
$arrAllCols[$key] = $$a; // set up array
}
// block index sets
$x = 1;
$y = 1;
for($i = 1; $i <= $size; $i++){
for($ii = 1; $ii <= $size; $ii++){
$a = “blockIndex_” . $x; // set up variable names
$z = 1;
for($iii = 1; $iii <= $size; $iii++){
for($iv = 1; $iv <= $size; $iv++){
${$a}[$z++] = $y; // set up variable
$y = $y + 1;
}
$y = $y + ((pow($size, 2)) - ($size));
}
$arrAllBlocks[$x] = $$a; // set up array
$x = $x + 1;
}
$y = ($i * $size) + 1;
}
// set up basic board
for($i = 1; $i <= pow($size, 2); $i++){
foreach($arrAllBlocks as $block){
$temp = $numbers;
foreach($block as $index){
$data[$index] = array_shift($temp);
}
$firstNumber = array_shift($numbers);
$numbers = array_pad($numbers, pow($size, 2), $firstNumber);
}
}
ksort($data);
// shuffle rows
for($i = 0; $i <= $size - 2; $i++){
foreach($arrAllRows as $arrRows){
shuffle($arrRows);
$arrRows = array_slice($arrRows, 0, 2); // takes first 2 rows
foreach($arrRows as $key => $row){
foreach($row as $rowKey => $index){
if($key == 0){
$row_1[$rowKey] = $data[$index];
}else{
$row_2[$rowKey] = $data[$index];
}
}
}
foreach($arrRows as $key => $row){ // swops them
foreach($row as $rowKey => $index){
if($key == 0){
$data[$index] = $row_2[$rowKey];
}else{
$data[$index] = $row_1[$rowKey];
}
}
}
}
}
// shuffle columns
for($i = 0; $i <= $size - 2; $i++){
foreach($arrAllCols as $arrCols){
shuffle($arrCols);
$arrCols = array_slice($arrCols, 0, 2); // takes first 2 columns
foreach($arrCols as $key => $col){
foreach($col as $colKey => $index){
if($key == 0){
$col_1[$colKey] = $data[$index];
}else{
$col_2[$colKey] = $data[$index];
}
}
}
foreach($arrCols as $key => $col){ // swops them
foreach($col as $colKey => $index){
if($key == 0){
$data[$index] = $col_2[$colKey];
}else{
$data[$index] = $col_1[$colKey];
}
}
}
}
}
$solution = implode(”,”, $data);
//remove pairs of numbers symetrically
if($difficulty == 1){
$pairs = 16;
}elseif($difficulty == 2){
$pairs = 22;
}elseif($difficulty == 3){
$pairs = 30;
}else{
$pairs = 170;
}
for($i = 1; $i <= $pairs; $i++){
do{
$number_1 = rand(1, pow($size, 4));
}while($number_1 == (((pow($size, 4) - 1) / 2) + 1));
$data[$number_1] = ‘’;
$number_2 = (pow($size, 4) + 1) - $number_1;
$data[$number_2] = ‘’;
}
$puzzle = implode(”,”, $data);
}
