[Blackjack] Time limit

<?
error_reporting(E_ALL & ~E_NOTICE);
mt_srand(123);

$start=microtime();

$dummy=array();
for ($a=0; $a<70000; $a++) {
    $n=$a%3;
    if ($n==0) {
        $dummy[mt_rand(0,100)][mt_rand(0,100)]=mt_rand(0,100);
    } else
    if ($n==1) {
        $source=mt_rand(0,100);
        $target=mt_rand(0,100);
        $tmp=$dummy[$source];
        $dummy[$source]=$dummy[$target];
        $dummy[$target]=$tmp;
    } else
    if ($n==2) {
        $which=mt_rand(0,100);
        if (is_array($dummy[$which]))
            asort($dummy[$which]);
    }
}

$end=microtime();

list($a,$b)=explode(" ", $start);
list($c,$d)=explode(" ", $end);

echo ($c+$d-$a-$b)." seconds...n";


?>