[RESOLVED] get period length of a number (math.)

[Reiners]

Hi!

Lets say I have an array full with 256 different numbers and want to find out if there is any period and if so, how long this period is.

example:
array (0,3,6, 7,1,3,6,2,5, 7,1,3,6,2,5, 7,1,3,6,2,5, 7,1,3,6,2,5 .....);

notice the period 7,1,3,6,2,5 --> period length would be "6". Notice also, that the first numbers "0,3,6" dont belong to a period.

How can you find this length of a period in PHP? Unfortunetly I havent found a function for this 😉 Thanks for helping!

Cheers,
Reiners

edit: the title says "period length of a number" to make the problem more clearly ... of course you can also implode the array to one number and than find the period if that make things easier 😉

[NogDog]

Here's something to play with:

function find_period($array, $maxShift)
{
   for($size = 1; $size <= floor(count($array)/2); $size++)
   {
      $chunks = array_chunk($array, $size);
      if(count($chunks[count($chunks)-1]) < $size)
      {
         array_pop($chunks);
      }
      $found = TRUE;
      for($ix = 1; $ix < count($chunks); $ix++)
      {
         if(implode('', $chunks[0]) != implode('', $chunks[$ix]))
         $found = FALSE;
      }
      if($found)
      {
         return($size);
      }
   }
   if($maxShift)
   {
      array_shift($array);
      return(find_period($array, --$maxShift));
   }
   return(FALSE);
}
$test = array (0,3,6, 7,1,3,6,2,5, 7,1,3,6,2,5, 7,1,3,6,2,5, 7,1,3,6);
$result = find_period($test, 5); // 5 is max number of initial values you're willing to ignore
echo ($result === FALSE) ? "No period found" : "Period = $result";

[Reiners]

thank you very very much for that code.
works great !
thumbs up