Get path from adjacency list data - php

Question

I have an array (data from adjacency table) and it looks like:
Array
(
[0] => Array
(
[id] => 1
[name] => Anniversary
[parent] => 0
)
[1] => Array
(
[id] => 12
[name] => New arrives
[parent] => 1
)
[2] => Array
(
[id] => 13
[name] => Discount
[parent] => 12
)
[3] => Array
(
[id] => 6
[name] => Birthday
[parent] => 0
)
)
And I'm looking for the way to retrieve my path by ID;
For example: getPath(13): Anniversary->New arrives->Discount;
For example: getPath(12): Anniversary->New arrives;
For example: getPath(1): Anniversary;
For example: getPath(6): Birthday;
How can I do this?
Thanks!

Answer 1

function getpath($id, $arr, $level = 0) {
$result = array();
foreach($arr as $key => $value){
if($id == $value['id']){
$result[] = $value['name'];
$id = $value['parent'];
if($id != 0){
$result = array_merge($result, getpath($id, $arr, $level+1));
}else{
break;
}
}
}
return $level ? $result : implode('->',array_reverse($result));
}
echo getpath(13,$arr);

Answer 2

Consider this array,
$input = [
['id'=>1, 'name'=>'Anniversary', 'parent'=>0],
['id'=>12, 'name'=>'New arrives', 'parent'=>1],
['id'=>13, 'name'=>'Discount', 'parent'=>12],
['id'=>6, 'name'=>'Birthday', 'parent'=>0]
];
and this function,
function path($element_id, $input, $ids = [])
{
if(!$ids) // for performance, make this once and pass it around
{
$ids = array_column($input, 'id'); // array containing only 'id's of $input
}
$current_key = array_search($element_id, $ids); // search for $input variable's current key
unset($ids[$current_key]); // unsetting used keys to make above array search faster next time
$current_element = $input[$current_key]; // get current element as array from $input
$names[] = $current_element['name']; // create an array containing current element
if($current_element['parent'] != 0) // check if current element have parent
{
$names[] = path($current_element['parent'], $input, $ids); // call this function, let it return string, append it to $names
}
return implode(' ⟶ ', array_reverse($names)); // make final return, seprate by ⟶
}
Reading echo path(13, $input); will return
Anniversary ⟶ New arrives ⟶ Discount
Here is minified version of the same function
function path($a,$b,$c=[]){if(!$c){$c=array_column($b,'id');}$d=array_search($a,$c);unset($c[$d]);$e=$b[$d];$f[]=$e['name'];if($e['parent']!=0){$f[]=path($e['parent'],$b,$c);}return implode(' ⟶ ',array_reverse($f));}
Thanks to code reviewers Loufylouf and Quill

Answer 3

$find = 13;
$path = array();
function FindById ($arr, $find) {
$k = null;
foreach($arr as $key => $item)
if ($item['id'] == $find)
{ $k = $key; break; }
return $k;
}
if ( false === ($k = FindById($arr, $find))) die("not found");
while (true) {
array_unshift($path, $arr[$k]['name']);
if( ! $arr[$k]['parent']) break;
if(false === ($k = FindById($arr, $arr[$k]['parent']))) die("illegal structure");
}
echo implode('->', $path);