Fairly hard one to explain, but effectively I've got an array of items which have IDs, of which can contain a list of IDs for other array items. for example
$items = [
[id: 'one', deps: ['three']],
[id: 'two'],
[id: 'three', deps: ['four', 'two']],
[id: 'four']
];
So as you can see here, one depends on three, and three depends on four and two.
I need to get a new array, that contains these items in order - so that the dependencies are listed in order. So the above array would convert into
$items = [
[id: 'four'],
[id: 'two'],
[id: 'three', deps: ['four', 'two']],
[id: 'one', deps: ['three']]
];
How would I complete this? I've tried various while loops checking for item positions, but can't crack it.
Thanks
UPDATE Some people have said its a duplicate question of THIS but the main difference being the above example has multiple dependencies - whereas the mentioned thread only works on a single string dependency
you can use a function like this, that iterates until all dependencies are met, or no more dependencies can be resolved:
$items = array(array('id' => 'one', 'deps' => array('three')),
array('id' => 'two'),
array('id' => 'three', 'deps' => array('four', 'two')),
array('id' =>'four'));
$sortedItems = sortDeps($items);
var_dump($sortedItems);
function sortDeps($items) {
$res = array();
$doneList = array();
// while not all items are resolved:
while(count($items) > count($res)) {
$doneSomething = false;
foreach($items as $itemIndex => $item) {
if(isset($doneList[$item['id']])) {
// item already in resultset
continue;
}
$resolved = true;
if(isset($item['deps'])) {
foreach($item['deps'] as $dep) {
if(!isset($doneList[$dep])) {
// there is a dependency that is not met:
$resolved = false;
break;
}
}
}
if($resolved) {
//all dependencies are met:
$doneList[$item['id']] = true;
$res[] = $item;
$doneSomething = true;
}
}
if(!$doneSomething) {
echo 'unresolvable dependency';
}
}
return $res;
}