5 random numbers that don't occur in an array

[timvdalen]

Hi all.

I've got a bit of a though one here.

I want to create 5 random numbers (1,45) every time a script is executed.

The hard part is that it can only be numbers that don't occur in an array.

 

This is what I currently have:

   $newqs = array(rand(1,$qcount),rand(1,$qcount),rand(1,$qcount),rand(1,$qcount),rand(1,$qcount));

   $okay = false;

   while($okay == false){
      $i = 0;
      while($i <5){
         if(in_array($newqs[$i], $questions)){
            $okay = false;
            $newqs[$i]++;
         }else{
            $okay = true;
         }
         $i++;
      }
   }

$questions is the array with the numbers that have already been chosen.

I'll be adding the picked numbers to the array afterwards.

 

I think that the problem with this method is that it's possible that two of the same numbers are picked. Right now, I'm having a bit of trouble with coming up with a better way to check if the number was already picked.

 

Any ideas will be appreciated.

 

Thanks

[timvdalen]

I realize that this is not really a beginner problem, so I'm going to bump this hoping that some more experienced users see this

[Wolphie]

<pre>
<?php
$numbers = array(rand(1, 45),rand(1, 45),rand(1, 45),rand(1, 45),rand(1, 45));
$questions = array(rand(1, 45),rand(1, 45),rand(1, 45),rand(1, 45),rand(1, 45));

print_r($numbers);
print_r($questions);

$i = 0;

while (true) {
  if ($i == count($numbers)) {
    break;
  }
  else {
    if (!in_array($numbers[$i], $questions)){
      break;
    }
    else {
      echo 'Found!';
    }
  }
  
  $i++;
}
?>
</pre>

 

Result:

Array
(
    [0] => 5
    [1] => 6
    [2] => 36
    [3] => 41
    [4] => 12
)
Array
(
    [0] => 7
    [1] => 5
    [2] => 27
    [3] => 38
    [4] => 37
)
Found!

 

Note: The number 5 occurred in both arrays, therefore "Found!" was displayed on page.

[timvdalen]

Thanks for your input.

I'm quite sure that your code and my code so far do the same (although I guess yours is faster, thanks). The problem I have is what to put at the place where you let the code echo found. I now let it increase, but this will result in an unwanted output in the case that $numbers[$i] equals 45 or two or more of the generated numbers are the same.

I could go around this by making it 1 if it's 45 and that's already picked or just replacing $newqs[$i]++ by $newqs[$i]=rand(1,45) but I'm pretty sure these are both pretty slow.

[salathe]

Here's an alternative idea:

 

$pool = range(1, 45);
$questions = array(5, 9, 10, 12, 33, 39);

// Get a list of questions from the pool that have not already been asked
$available = array_diff($pool, $questions);

// Get five random questions from the list of available ones
$random = array_rand(array_flip($available), 5);

print_r($random);

[timvdalen]

Thanks! That's way quicker and way easier.

I really gotta read up on all the array_ functions