Algorithm help

[uidzer0b]

Hey everyone,

 

I'm a long time lurker, first time poster I'm having a little trouble writing an algorithm to create a hierarchal structure from a database which looks like this:

 

      parent_id | child_id    |
----------------+-------------+
              1 |           2 |
              2 |           3 |
              3 |           4 |
              3 |           5 |
              5 |           6 |
              5 |           7 |

 

So coming out of the database, I get an array which looks like this:

 

Array
(
    [0] => Array
        (
            [parent_id] => 1
            [child_id] => 2
        )

    [1] => Array
        (
            [parent_id] => 2
            [child_id] => 3
        )

    [2] => Array
        (
            [parent_id] => 3
            [child_id] => 4
        )
...

 

I would like to put this into an array which represents the following structure:

 

1
\
  2
   \
    3
   / \
  4   5
     / \
   6    7 

 

Can anyone point me in the right direction? Let me know if this isn't clear - I can try to elaborate.

 

Thanks!

 

Ben

[Psycho]

Putting that data into an array in that manner will be problematic because you are going to end up with nothing but a bunch of arrays with null values. For example $array[1][2][3] must be an array because it has two child records (4 and 5).

 

So $array[1][2][3][4] = ???

 

What exaclty are you planning to do with the array that you can't accomplish fro the data in the database?

[sasa]

try

<?php 
$input = array(
array('parent_id' => 1, 'child_id' => 2),
array('parent_id' => 2, 'child_id' => 3),
array('parent_id' => 3, 'child_id' => 4),
array('parent_id' => 3, 'child_id' => 5),
array('parent_id' => 5, 'child_id' => 6),
array('parent_id' => 5, 'child_id' => 7)
);

function my_tree($input, $start = false) {
//find start node
$p = array();
$c = array();
foreach ($input as $key => $v) {
	$p[$key] = $v['parent_id'];
	$c[$key] = $v['child_id'];
}
if ($start === false){
	$start = array_diff($p,$c);
	$start = array_unique($start);
}
foreach ($start as $parent) {
	$keys = array_keys($p, $parent);
	$tmp = array();
	foreach ($keys as $k) {
		$tmp1 = my_tree($input, array($c[$k]));
		echo '';
		$tmp = array_merge($tmp, $tmp1);
	}
	if (count($tmp)==0) {
		$out[] = array('ID' => $parent);
	} else $out[]=array('ID' => $parent, 'CHILDs' => $tmp);
}
return $out;
}

$a = my_tree($input);
print_r($a);
?>