Calculating the depth of an element in an associative array with php - php

Question

I've been trying unsuccessfully to write a recursive function to give me the depth of a given element. I just can't seem to get my head around the recursion. This is what I have, but it's not working correctly:
function getDepth($a, $e, $depth = 0) {
foreach ($a as $key => $val) {
if (is_array($val)) {
if ($key == $e) {
return $depth;
}
return getDepth($val, $e, $depth + 1);
}
else {
if ($val == $e) {
return $depth;
}
else {
return 1;
}
}
}
}
Can anyone please help point out what I'm doing wrong here? Thanks in advance for your help.
EDIT:
#Brad #Amber #Viktor Thanks, but this doesn't seem to be working either. Here's what I'm after... I have an array that looks like this:
[antonio] => Array
(
[ian] => Array
(
[molly] => Array
(
[blake] => blake
)
)
[shonda] => Array
(
[dana] => dana
[james] => james
)
[nels] => Array
(
[jason] => jason
[danny] => danny
)
[molly] => Array
(
[blake] => blake
)
[blake] => blake
[travis] => travis
)
It's a tree, and I'm hoping to find the depth level of a given name. So, I'll need to pass in a name, say blake. Then I'll want to traverse the whole tree keeping track of blake's depth whenever I find it as he could be (and indeed is in this example) in the tree at different levels. Assuming that the top-most depth level is 0, blake's level under antonio => ian => molly => blake is 3, but his level under antonio => blake is 1, so I would want to return 1. I will have to traverse the entire tree (luckily this function will not be called very often) to make sure that I've found the most shallow depth in the tree for the given user. Thanks again for your help.

Answer 1

Basically, to get the recursion right, if you know you have an array within your function, run your same function on it. We add the deepest path so far +1. In the end, you get what you are looking for.
function getDepth($a) {
$max=0;
foreach ($a as $val) {
if (is_array($val)) {
$tmp_depth=getDepth($val);
if ($max<($tmp_depth)) {
$max=$tmp_depth;
}
}
}
return $max+1;
}
I haven't benchmarked this or anything. Undoubtedly there could be speed improvements, if it is important.

Answer 2

function getDepth($a, $e, $depth = 0) {
$lower = false; // meaning 'not found'
// as you are looking for the less deep value, first check for values and then for arrays
// so there are chances when you do not traverse all the tree for a match
foreach ($a as $key => $val) if ($val == $e) return $depth;
foreach ($a as $key => $val) {
if (is_array($val)) {
$tmp = getDepth($val, $e, $depth + 1);
if($tmp) if ($lower === false || $tmp < $lower) $lower = $tmp;
}
}
return $lower;
}
$x=array(
antonio => Array(
ian => Array(
molly => Array(
blake => blake,
jhonyDeep => jhonyDeep
)
),
shonda => Array(
dana => dana,
james => james
),
nels => Array (
jason => jason,
danny => danny
),
molly => Array(
blake => blake
),
blake => blake,
travis => travis
)
);
echo getDepth($x, blake); // gives 1
echo getDepth($x, danny); // gives 2
echo getDepth($x, jhonyDeep); // gives 3

Answer 3

similar to my previous anwser but optimized for performance (and be careful, not tested)
function getDepth($a, $e, $depth = 0, $lower = false) {
// $lower = false means 'not found'
// as you are looking for the less deep value, first check for values and then for arrays
// so there are chances when you do not traverse all the tree for a match
foreach ($a as $key => $val) if ($val == $e) return $depth;
foreach ($a as $key => $val) {
if (is_array($val)) {
$tmp = false;
if($lower===false || $lower > $depth) $tmp = getDepth($val, $e, $depth + 1, $lower); // to do not recurse innecesary
if($tmp) {
if($tmp==$depth+1) return $tmp; //optimization: $depth+1 can't be beat by other values
if ($lower === false || $tmp < $lower) $lower = $tmp;
}
}
}
return $lower;
}
$x=array(
antonio => Array(
ian => Array(
molly => Array(
blake => blake,
jhonyDeep => jhonyDeep
)
),
shonda => Array(
dana => dana,
james => james
),
nels => Array (
jason => jason,
danny => danny
),
molly => Array(
blake => blake
),
blake => blake,
travis => travis
)
);
echo getDepth($x, blake); // gives 1
echo getDepth($x, danny); // gives 2
echo getDepth($x, jhonyDeep); // gives 3