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run code in 300+ PHP versions simultaneously
<?php $old_arr=array(1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20); $size = count($old_arr); print_r($size); for($i=0;$i<=19;$i++){ if ($i<=4){ $a[] = $old_arr[$i]; }elseif ($i>4 && $i<=9){ $b[] = $old_arr[$i]; }elseif ($i>9 && $i<=14){ $c[] = $old_arr[$i]; }elseif ($i>14){ $d[] = $old_arr[$i]; } } print_r($a); print_r($b); print_r($c); print_r($d); $new_arr = array(); $group_order[] = array(); while(count($new_arr)<$size){ foreach ($group_order as $i => $value) { unset($group_order[$i]); } $group_order = array_values($group_order); $group_order[] = mt_rand(1,4); while(count($group_order)<4){ $x=mt_rand(1,4); if(in_array($x,$group_order) == false){ $group_order[] = $x; } } $temp = $group_order; print_r($temp); foreach ($group_order as $value){ if ($value == 1){ $idx = mt_rand(0,(count($a)-1)); $new_arr[] = $a[$idx]; unset($a[$idx]); $a = array_values($a); }elseif ($value == 2){ $idx = mt_rand(0,(count($b)-1)); $new_arr[] = $b[$idx]; unset($b[$idx]); $b = array_values($b); }elseif ($value == 3){ $idx = mt_rand(0,(count($c)-1)); $new_arr[] = $c[$idx]; unset($c[$idx]); $c = array_values($c); }elseif ($value == 4){ $idx = mt_rand(0,(count($d)-1)); $new_arr[] = $d[$idx]; unset($d[$idx]); $d = array_values($d); } } } print_r($new_arr); ?>

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35.17 ms | 402 KiB | 5 Q