打印阵列时超出最大执行时间

Question

I have the following code, which prints all combinations of the given numbers. It returns a fatal error when $numbers contains two equal numbers.

I get the following error:

Fatal error: Maximum execution time of 30 seconds exceeded in
C:/Apache24/htdocs/index.php on line 18

My Code:

<?php
$numbers = array("2","1","4");
$numberofelements = count($numbers);
$factorial = 1;
for ($i=1; $i<=$numberofelements; $i++)
{
         $factorial *= $i;
}
$quantitycombinations = $factorial;
$numbersdrawn = array();
while(true)
{
    $exists = false;
    $numberdrawn1 = "";
    shuffle($numbers);
    $numberdrawn1 = implode("", $numbers);
    strval($numberdrawn1);
    foreach ($numbersdrawn as $value) {
            if(strval($value)==$numberdrawn1)
            {
                $exists = true;
            }
        }
    if(!$exists){
        array_push($numbersdrawn, $numberdrawn1);
        if(count($numbersdrawn)==$quantitycombinations)
        {
            foreach($numbersdrawn as $item)
            {
                echo $item."<br>";          
            }
            break;
        }
    }
}
?>

Answer 1

The while loop doesn't stop until the number of combinations in $numbersdrawn is equal to $factorial. But when there are duplicates, there aren't that many different combinations, because some of the combinations are identical to each other.

E.g. if the numbers are 1, 2, 3, the combinations are 123, 132, 213, 231, 312, 321.

But if the numbers are 1, 2, 2, the combinations are only 122, 212, 221.

You need to divide $factorial by the number of repeated elements to get $quantitycombinations.