[RESOLVED] Need a variable recursive algorithm - brain teaser

jkurrle

I have a data feed that can have a repetetive array structure nested up to 4 or 5 levels deep. Sometimes, the data stops at the first level, but it can go 2 or more times deeper. To further complicate the matter, when testing at each level, there can be 3 alternate outcomes at each level: 1) There is no further branching 2) there is a single branch or 3) there are multiple branches. Let me show you some of the possible array structures below:

[groups][group][subjects][subject]

[groups][group][groups][group][subjects][subject]

[groups][group][1][groups][group][subjects][subject]

[groups][group][0][groups][group][1][subjects][subject]

[groups][group][1][groups][group][groups][group][0][subjects][subject]

[groups][group][0][groups][group][1][groups][group][groups][group][subjects][subject]

[groups][group][groups][group][1][subjects][subject]

As you can see, the [groups][group] array structure varies on any given iteration of data that I import. I built a test to determine which of three outcomes is at each level, but I am stumped on how to recurse it through the tree, as each branch has 3 possible outcomes at every level. Can someone point me out a basic methodology or algorithm that can do this? Otherwise, I'll have to write out the complete tree of possibilities, which is a huge waste of code...

Any assistance would be greatly appreciated!

johanafm

This simple function recurses over all elements no matter the nest level. Is this what you're after?

$arr = array(
			'1',
			array('2.1', '2.2'),
			array(
				array('3.1.1', '3.1.2')
			)
		);

function walk($arr)
{
	if (!is_array($arr))
		echo $arr . '<br/>';
	else
	{
		foreach($arr as $val)
			walk($val);
	}
}

walk($arr);

jkurrle

Thanks for the quick reply. Not sure if this is exactly what I need, but it certainly gives me some great ideas! Thanks again!

jkurrle

Ok, let's complicate this just a little bit more...

Is there a way to keep track of where the pointer is in the array structure? So it would know it was at [arrayLevelOne][arrayLevel2][arrayLevelX]? I'm looking at using some sort of conditional to test for data at a certain level within the array tree.

Any ideas?

johanafm

Just add a function parameter with default value 0. Add 1 every time you recurse.

function walk($arr, $nestLevel = 0)
{
    if (!is_array($arr))
        printf('(&#37;d) %s<br/>', $nestLevel, $arr);
    else
    {
        foreach($arr as $val)
            walk($val, $nestLevel + 1);
    }
}

jkurrle

Thanks for that. I'm actually passing in an array as well, so I can parse information together from different levels within the array. Your examples were just what I needed. Thanks!