Group flat array elements separated by elements containing negative values into subarrays

Question

Having array in input so formed:

Array
(
    [0] => 10
    [1] => -1
    [2] => -1
    [3] => -1
    [4] => -1
    [5] => 15
    [6] => 16
    [7] => 17
    [8] => -1
    [9] => -1
    [10] => 20
)

How I can split it for -1 value having as output something so:

Array
(
    [0] => 10
    [1] => Array
        (
            [0] => 15
            [1] => 16
            [2] => 17
        )
    [2] => Array
        ( 
            [0] => 20
        )
)

The php explode() function works for string input. While here is something for array.

Are you just trying to remove any -1s from the array and leave it otherwise unchanged? It's not quite clear what you need due to the inconsistency in the output. — bcmcfc
– bcmcfc, Commented Nov 19, 2016 at 12:37

user7181041 · Accepted Answer · 2016-11-19 12:29:28Z

1

  1 <?php
  2     $array = [10, -1, -1, -1, -1, 15, 16, 17, -1, -1, 20];
  3     $tempArray = [];
  4     $result = [];
  5     foreach($array as $item)
  6     {
  7         if($item == -1)
  8         {
  9             if(count($tempArray))
 10             {
 11                 $result[] = $tempArray;
 12                 $tempArray = [];
 13             }
 14         }
 15         else
 16             $tempArray[] = $item;
 17 
 18     }
 19     if(count($tempArray))
 20     {
 21         $result[] = $tempArray;
 22     }
 23     echo json_encode($result);

and the result is,

~$ php cal.php 
[[10],[15,16,17],[20]]

answered Nov 19, 2016 at 12:29

user7181041

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4 Comments

Xorifelse Over a year ago

Almost, except in the desired output index 0 is a value, not an array.

user7181041 Over a year ago

yeah here is not sure, if there are more than one non -1 element at the begin of the array?

Marcello Impastato Over a year ago

Work very fine! Thanks.

Marcello Impastato Over a year ago

-1 element work as "delimiter" inside array. I done example with explode(). for string it split for give delimiter. For array delimiter in this case is -1.

Talha Abrar · Accepted Answer · 2016-11-19 13:00:16Z

Well here is solution for you.

$myAry = array(
    '0' => 10,
    '1' => -1,
    '2' => -1,
    '3' => -1,
    '4' => -1,
    '5' => 15,
    '6' => 16,
    '7' => 17,
    '8' => -1,
    '9' => -1,
    '10' => 20
);

$newAry = Array();

function splitArray($ary , $index){
    global $newAry;
    if($index == count($ary)){
        return $newAry;
    }
    if( $ary[$index] != -1 ){
        $chunk = array();
        while(  $index < count($ary) && $ary[$index] != -1 ){
            array_push($chunk , $ary[$index]);
            $index++;
        }
        array_push($newAry , $chunk);
        splitArray($ary , $index);

    } else {
        $index++;
        splitArray($ary , $index);
    }
}


splitArray($myAry , 0);
print_r($newAry);

output:

Array ( 
[0] => Array ( [0] => 10 ) 
[1] => Array ( [0] => 15 [1] => 16 [2] => 17 ) 
[2] => Array ( [0] => 20 ) 
      )

Benoti · Accepted Answer · 2016-11-19 12:42:23Z

0

It's not exactly the same result, using array_unique and unset

$array = array_unique($array);

foreach ($array as $k=>$item) {
   if($item == '-1'){
      unset($array[$k]);
   }
}

Output

array(5) {
  [0]=>
  int(10)
  [5]=>
  int(15)
  [6]=>
  int(16)
  [7]=>
  int(17)
  [10]=>
  int(20)
}

answered Nov 19, 2016 at 12:42

Benoti

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1 Comment

Marcello Impastato Over a year ago

Not need remove -1 value from array but split array for -1 value. For to be more right, think to explode() function. It work for string but suppose to have an array and not a string. The result should to be something as: explode ($delimiter, $array) but of course explode make an array splitting a string for delimeter. In this case (as i asked) explode make an array starting from an array splitting it for give value.

mickmackusa · Accepted Answer · 2024-10-06 23:21:20Z

0

To avoid tedious result array element counting and keeping track of result indexes, only push references into the result array when there is no reference declared. When a -1 value is encountered, destroy the reference so that the next qualifying value is encountered, it goes into a new group. Demo

$array = [10, -1, -1, -1, -1, 15, 16, 17, -1, -1, 20];
$result = [];
foreach ($array as $v) {
    if ($v === -1) {
        unset($ref);
        continue;
    }
    if (!isset($ref)) {
        $result[] =& $ref;
    }
    $ref[] = $v;
}
var_export($result);

Output:

array (
  0 => 
  array (
    0 => 10,
  ),
  1 => 
  array (
    0 => 15,
    1 => 16,
    2 => 17,
  ),
  2 => 
  array (
    0 => 20,
  ),
)

answered Oct 6, 2024 at 23:21

mickmackusa♦

49.2k13 gold badges98 silver badges165 bronze badges

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