Php checkerboard spiral display with array - php

Question

So I'm looking how to make a checkboard but with a spiral in it instead of the default checkerboard made like this:
$checkerboard=array();
for($row=0;$row<10;$row++){
if($row%2==0){
for($col=0;$col<10;$col++){
if($col%2==0){
$checkerboard[$row][$col]="white";
}else{
$checkerboard[$row][$col]="black";
}
}
}else{
for($col=0;$col<10;$col++){
if($col%2==0){
$checkerboard[$row][$col]="black";
}else{
$checkerboard[$row][$col]="white";
}
}
}
}
I also tried it with 2 diagonals like this:
$diagonal=array();
for($row=0;$row<10;$row++){
for($col=0;$col<10;$col++){
if($row==$col){
$diagonal[$row][$col]='black';
}else{
$diagonal[$row][$col]='white';
}
if($row+$col==9){
$diagonal[$row][$col]='black';
}
}
}
And then echo'd simply like this:
echo "<table>";
for($row=0;$row<count($checkerboard);$row++){
echo "<tr>";
for($col=0;$col<count($checkerboard);$col++){
echo "<td width='50px' height='50px' bgcolor='".$checkerboard[$row][$col]."'></td>";
}
echo "</tr>";
}
I'd like to keep the code simple because I've not been coding php for a very long time and it has to work with an array.
I tried this here:
$spiral=array();
for($row=0;$row<10;$row++){
for($col=0;$col<10;$col++){
$spiral[$row][$col]='white';
if($row==0 or $row==9 or $col==0 or $col==9){
$spiral[$row][$col]='black';
}if($row==1 and $col==0){
$spiral[$row][$col]='white';
}if($row==2 and $col<8){
$spiral[$row][$col]='black';
}if($row>1 and $row<8 and $col==7){
$spiral[$row][$col]='black';
}if($row==7 and $col>1 and $col<8){
$spiral[$row][$col]='black';
}if($row>3 and $row<7 and $col==2){
$spiral[$row][$col]='black';
}if($row==4 and $col>2 and $col<6){
$spiral[$row][$col]='black';
}if($row==5 and $col==5){
$spiral[$row][$col]='black';
}
}
}
But if the checkerboard becomes bigger it will be very hard to change. It there a way to make it easier?

Answer 1

Try this out:
I create an empty board then start drawing horizontal & vertical lines, starting from the edges each time. The code might need some tweaking but it's a good start
$checkerboard=array();
$size = 12;
for ($row=0; $row<$size; $row++) {
for ($col=0; $col<$size; $col++) {
$checkerboard[$row][$col]="red";
}
}
//horizontal
$pair = 0 ;
while ($pair < (int) $size / 2) {
//drawing top half rows
$row = 2 * $pair;
$end = min($row, $size - $row);
$start = $end - 2;
for ($col = $start; ($col < $size - $end) && ($row < $size / 2); $col++){
$checkerboard[$row][$col]="black";
}
//drawing bottom half rows
$far_row = $size - 1 - 2 * $pair;
$end = min($far_row, $size - $far_row) + 1 - 2;
$start = $end ;
for ($col = $start; ($col < $size - $end) && ($far_row > $size / 2 ); $col++){
$checkerboard[$far_row][$col]="black";
}
$pair++;
}
$pair = 0;
//vertical
while ($pair < (int) $size / 2) {
//drawing left half columns
$col = 2 * $pair;
$end = min($col, $size - $col);
$start = $end +2 ;
for ($row = $start; ($row < $size - $end) && ($col < $size / 2); $row++){
$checkerboard[$row][$col]="black";
}
//drawing right half columns
$far_columns = $size - 1 - 2 * $pair;
$end = min($far_columns, $size - $far_columns) - 1;
$start = $end ;
for ($row = $start; ($row < $size - $end) && ($far_columns >= ($size / 2 ) ); $row++){
$checkerboard[$row][$far_columns]="black";
}
$pair++;
}
echo "<table>";
for($row=0;$row< $size;$row++){
echo "<tr>";
for($col=0; $col< $size; $col++){
echo "<td width='50px' height='50px' bgcolor='".$checkerboard[$row][$col]."'></td>";
}
echo "</tr>";
}
You can just change the $size variable for different dimensions

Answer 2

Here is my attempt at the problem:
function buildSpiral($gridSize)
{
/**
* Origin is at the top left handcorner
*/
$x = 0;
$y = 0;
$xMin = 0;
$xMax = $gridSize-1;
$yMin = 2;
$yMax = $gridSize-1;
$pattern = [];
$size = $gridSize;
$collision = function($p, $limit) {
return (bool) ($p == $limit);
};
// increment x
$shadeRight = function(&$x, $y) use (&$pattern, &$xMin, &$xMax, $collision) {
if ($xMin > $xMax) {
return;
}
do {
$pattern[$y][$x] = 1;
} while (!$collision($x++, $xMax));
if ($x >= $xMax) {
$x=$xMax;
}
$xMax-=2;
};
// increment y
$shadeDown = function($x, &$y) use (&$pattern, &$yMin, &$yMax, $collision) {
while ($y < $yMax && $yMin > $yMax) {
$pattern[++$y][$x] = 1;
}
if ($yMin > $yMax) {
return;
}
do {
$pattern[$y][$x] = 1;
} while (!$collision($y++, $yMax));
if ($y >= $yMax) {
$y = $yMax;
}
$yMax-=2;
};
// decrement x
$shadeLeft = function(&$x, $y) use (&$pattern, &$xMin, &$xMax, $collision, $gridSize) {
if ($xMin > $xMax) {
return;
}
do {
$pattern[$y][$x] = 1;
} while (!$collision($x--, $xMin));
if ($x < $xMin) {
$x=$xMin;
}
$xMin+=2;
};
// decrement y
$shadeUp = function($x, &$y) use (&$pattern, &$yMin, &$yMax, $collision, $gridSize) {
while ($y > $yMin && $yMin > $yMax) {
$pattern[--$y][$x] = 1;
}
if ($yMin > $yMax) {
return;
}
do {
$pattern[$y][$x] = 1;
} while(!$collision(--$y, $yMin));
if ($y < $yMin) {
$y = $yMin;
}
$yMin+=2;
};
while ($size > 0) {
$shadeRight($x, $y);
$shadeDown($x, $y);
$shadeLeft($x, $y);
$shadeUp($x, $y);
$size-=2;
}
return $pattern;
}
for ($i = 1; $i <= 25; $i++) {
$checkboard = buildSpiral($i);
echo "<h1>$i</h1>";
echo "<table style='margin-bottom: 2em;'>";
for($row=0;$row<count($checkboard);$row++){
echo "<tr>";
for($col=0;$col<count($checkboard);$col++){
if (!isset($checkboard[$row][$col])) {
echo "<td width='50px' height='50px' bgcolor=\"red\"></td>";
} else {
echo "<td width='50px' height='50px' bgcolor=\"black\"></td>";
}
}
echo "</tr>";
}
echo "</table>";
}
I stop each shading direction when a limit is hit.
Update Let's say I want the spirals to start from the top right corner, then we just need to set the new origin and call the shaders in the way we want the spiral to go like so:
function buildSpiral($gridSize)
{
/**
* Origin is at the top left handcorner
*/
$x = $gridSize-1;
$y = 0;
$xMin = 0;
$xMax = $gridSize-1;
$yMin = 2;
$yMax = $gridSize-1;
$pattern = [];
$size = $gridSize;
$collision = function($p, $limit) {
return (bool) ($p == $limit);
};
// increment x
$shadeRight = function(&$x, $y) use (&$pattern, &$xMin, &$xMax, $collision) {
if ($xMin > $xMax) {
return;
}
do {
$pattern[$y][$x] = 1;
} while (!$collision($x++, $xMax));
if ($x >= $xMax) {
$x=$xMax;
}
$xMax-=2;
};
// increment y
$shadeDown = function($x, &$y) use (&$pattern, &$yMin, &$yMax, $collision) {
while ($y < $yMax && $yMin > $yMax) {
$pattern[++$y][$x] = 1;
}
if ($yMin > $yMax) {
return;
}
do {
$pattern[$y][$x] = 1;
} while (!$collision($y++, $yMax));
if ($y >= $yMax) {
$y = $yMax;
}
$yMax-=2;
};
// decrement x
$shadeLeft = function(&$x, $y) use (&$pattern, &$xMin, &$xMax, $collision, $gridSize) {
if ($xMin > $xMax) {
return;
}
do {
$pattern[$y][$x] = 1;
} while (!$collision($x--, $xMin));
if ($x < $xMin) {
$x=$xMin;
}
$xMin+=2;
};
// decrement y
$shadeUp = function($x, &$y) use (&$pattern, &$yMin, &$yMax, $collision, $gridSize) {
while ($y > $yMin && $yMin > $yMax) {
$pattern[--$y][$x] = 1;
}
if ($yMin > $yMax) {
return;
}
do {
$pattern[$y][$x] = 1;
} while(!$collision(--$y, $yMin));
if ($y < $yMin) {
$y = $yMin;
}
$yMin+=2;
};
while ($size > 0) {
$shadeLeft($x, $y);
$shadeDown($x, $y);
$shadeRight($x, $y);
$shadeUp($x, $y);
$size-=2;
}
return $pattern;
}
for ($i = 1; $i <= 25; $i++) {
$checkboard = buildSpiral($i);
echo "<h1>$i</h1>";
echo "<table style='margin-bottom: 2em;'>";
for($row=0;$row<count($checkboard);$row++){
echo "<tr>";
for($col=0;$col<count($checkboard);$col++){
if (!isset($checkboard[$row][$col])) {
echo "<td width='50px' height='50px' bgcolor=\"red\"></td>";
} else {
echo "<td width='50px' height='50px' bgcolor=\"black\"></td>";
}
}
echo "</tr>";
}
echo "</table>";
}