CODEWITHSUNDEEP
phparrays
Jenny
Jenny

Reputation: 1727

Will foreach become inefficient when number of array elements grow big?

Currently I'm using foreach to search key when use array_replace:

$grades = array(
               0 =>array('id'=>1, 'grade'=>4),
               1 =>array('id'=>5, 'grade'=>2), 
               2 =>array('id'=>17,'grade'=>1),
             )
$replacement = array('id'=>17,'grade'=>3);

foreach($grades as $key=>$grade){
    if($grade->id ==$replacement['id'] )
       $found = $key;
}
$new_grades = array_replace($grades, array($found_key=>$replacement));

I wonder if this will become inefficient when the number of elements grow too much in $grades array. Is there any better way to do the search and replace job?

Upvotes: 1

Views: 167

Answers (2)

Felix Kling
Felix Kling

Reputation: 816334

The execution time grows linearly with the number of elements in the array (O(N)). Use a better data structure, i.e. use the array in an associative way with the ID as index:

$grades = array(
    1 => array('grade'=>4),
    5 => array('grade'=>2), 
    17 => array('grade'=>1)
);

Then the lookup cost is constant (O(1)). You can do:

$grades[$replacement['id']] = array('grade' => $replacement['grade']);

or something similar, depending on your data.

Upvotes: 5

chaos
chaos

Reputation: 124277

Yeah, that can be done vastly more efficiently.

$grades = array(
    1   => 4,
    5   => 2,
    17  => 1,
);
$replacement = array(
    17  => 3,
);
$grades = array_merge($grades, $replacement);

If you need more information associated with the ID than just the grade, then you'll still need a more involved data structure like Felix Kling has. But no such requirement is present in your question so I'm not assuming it.

Upvotes: 4

Related Questions