Find the concentration areas of one's in a unitary matrix - php

Question

I've got some array of 0-1 elements like:
array('0,0'=>0,'1,0'=>0,'2,0'=>0,'3,0'=>1,'0,1'=>1,'1,1'=>1,'2,1'=>0,'3,1'=>0,'0,2'=>1,'1,2'=>1,'2,2'=>1,'3,2'=>1);
It looks like:
0 0 0 1
1 1 0 0
1 1 1 1
How to find all islands of 1?
In this case i would like to return values:
$island[] = array('3,0');
$island[] = array('0,1','1,1','0,2','1,2','2,2','3,2');
Of course in real cases are more expanded.
Thanks in advance.

Answer 1

$islands = [
[0, 0, 0, 1],
[1, 1, 0, 0],
[1, 1, 1, 1],
];
$result = [];
array_walk_recursive(
$islands,
function ($value, $key) use (&$result) {
static $c = PHP_INT_MAX;
static $r = -1;
if ($c >= $key) {
++$r;
$c = $key;
}
if ($value)
$result[] = $key . ',' . $r;
}
);
var_dump($result);

Answer 2

You can use a foreach inside another foreach to trawl the arrays for values of 1 like this:
<?php
$array=array(
array(0,0,0,1),
array(1,1,0,0),
array(1,1,1,1)
);
$island=array();
foreach($array as $x=>$arr)
{
foreach($arr as $y=>$val)
{
if($val==1)
{
$island[]=array($x, $y);
}
}
}
print_r($island);
?>
with the output:
Array
(
[0] => Array
(
[0] => 0
[1] => 3
)
[1] => Array
(
[0] => 1
[1] => 0
)
[2] => Array
(
[0] => 1
[1] => 1
)
[3] => Array
(
[0] => 2
[1] => 0
)
[4] => Array
(
[0] => 2
[1] => 1
)
[5] => Array
(
[0] => 2
[1] => 2
)
[6] => Array
(
[0] => 2
[1] => 3
)
)
This output finds all indexes of 1 and returns them as a a single entry in the array.
You can also use:
<?php
$array=array(
array(0,0,0,1),
array(1,1,0,0),
array(1,1,1,1)
);
$island=array();
$temp=array();
foreach($array as $x=>$arr)
{
foreach($arr as $y=>$val)
{
if($val==1)
{
$temp[]="'".$x.','.$y."'";
}
}
if(count($temp)>0)
{
$island[]=implode(',',$temp);
}
$temp=array();
}
print_r($island);
?>
Which will make an array closer to your required output:
Array
(
[0] => '0,3'
[1] => '1,0','1,1'
[2] => '2,0','2,1','2,2','2,3'
)