Question

So say I have the following array:

array(
    'key1'=>array(
        'key.1'=>'tester',
        'key.2'=>'tester'
    ),
    'key2'=>array(
        'key.1'=>'failedtester',
        'key.2'=>'tester'
    )
)

How do I search this array such that I return back the parent keys such that a value is a certain value based off a sub key?
e.g. Return the keys such that key.1 == tester (this would return key1)
e.g. Return the keys such that key.1 == failedtester (this would return key2)
e.g. Return the keys such that key.2 == tester (this would return array(key1, key2)

Is this possible without doing a for loop?

Edit: Using PHP (sorry thought I had said PHP, apparently not.. #fail)

Answer 1

Solution 1: two nested loops, total time complexity is O(n*n):

function search1($a, $key, $val) {
    $result = array();
    foreach ($a as $a_key => $a_arr) {
       foreach ($a_arr as $k => $v) {
           if ($k == $key && $v == $val) {
               $result[] = $a_key;
           }
        }
    }
    return $result;
}
$result = search1($a, "key.1", "tester"); // call

Solution 2: the inner loop is replaced by a lookup, total complexity is O(n*log(n)). This should be significantly faster for large n:

function search2($a, $key, $val) {
    $result = array();
    foreach ($a as $a_key => $a_arr) {
        if (array_key_exists($key, $a_arr) && $a_arr[$key] == $val) {
               $result[] = $a_key;
        }
    }
    return $result;
}
$result = search2($a, "key.1", "tester"); // call