Grouping array with consecutive keys

Question

I've an array like this -

 Array
(
    [16] => 424
    [17] => 404
    [18] => 416
    [21] => 404
    [22] => 456
    [23] => 879
    [28] => 456
    [29] => 456
    [32] => 123
    [35] => 465
)

The output of this array would be

Array
(
    [0] => Array
           (   ['start'] => 16
               ['stop'] => 19
           )
    [1] => Array
           (   ['start'] => 21
               ['stop'] => 24
           )
    [2] => Array
           (
               ['start'] => 28
               ['stop'] => 30
           )
    [3] => Array
           (
               ['start'] => 32
               ['stop'] => 33
           )
    [4] => Array
           (
               ['start'] => 35
               ['stop'] => 36
           )
)

I don't really need the values. Just grouping the keys.

The 'start' value should be the 'start' value itself. Whereas, the 'stop' value should be a consecutive integer.

And if consecutive integer doesn't exist for a particular key(like for [32] and [35]), 'stop' should be the integer+1 (same as above) .

Thank you all for help.

i dont know if your example is really consistent. for lonely integers shouldnt the stop/start be equal? — jon_darkstar
– jon_darkstar, Commented Jan 5, 2011 at 5:57

jon_darkstar · Accepted Answer · 2011-01-05 19:47:31Z

5

reset($arr);
$lastKey = key($arr);
$ansIndex = -1;
$ans = array();

foreach ($arr as $k=>$v)
{
    if ($k != $lastKey + 1)
    {
         $ansIndex++;
         $ans[$ansIndex]['start'] = $k; 
    }

    $ans[$ansIndex]['stop']  = $k+1;
    $lastKey = $k;
}

EDIT - changed $k to $k+1 for the stop indexes to reflect change in your question
EDIT - noticed i had a line of code within both if and else. taking it out of conditional since it runs regardless.

edited Jan 5, 2011 at 19:47

answered Jan 5, 2011 at 6:02

jon_darkstar

16.9k7 gold badges35 silver badges38 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

kapeels Over a year ago

This worked. Just a note, why is $lastKey set to -1? Putting reset($arr) and setting $lastKey to key($arr) did the trick. Please update your answer so I can accept it :)

jon_darkstar Over a year ago

ok sounds good. i just picked -1 as something that could be relied upon to be different

jon_darkstar Over a year ago

what changes do you want? where is this reset? cant be within the loop. key($arr) === $k at all times, so for clarity sake i wouldnt change one unless you are going to change every time

jon_darkstar Over a year ago

o nevermind, i see you are just talking about initialization. good idea i like that better than me pulling -1 out of my ass

Collectives™ on Stack Overflow

Grouping array with consecutive keys

1 Answer 1

4 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

4 Comments

Your Answer

Sign up or log in

Post as a guest

Related