php multi array

Question

What if I have a multidimensional array, in which I want to make combinations. So for example if I have 3 arrays:

Array(1,2)
Array(7,3)
Array(3,9,8,2)

Then I want a function which make combinations like: array( array(1,7) array(1,3) array( 3,9) etcetera but also array(7,3) array(7,9)

Plus it must check the availability so if the numbers are not available then do not make combinations with them.

Now I got this, and further I cant get:

   $xCombinations =
            Array(
                Array(1,2)
                Array(7,3)
                Array(3,9,8,2)
            );



            $available = Array([1] => 2,[2] => 1, [7]=>3,[3]=>4, [8]=>2, [2]=>4);

            $combination = Array();

            recursiveArray($xCombinations);

            function recursiveArray($tmpArr){
               if($tmpArr){
                 foreach ($tmpArr)as $value) {
                   if (is_array($value)) {
                      displayArrayRecursively($value);
                   } else {
                    //here 1st time $value would be 1, 
                    //so this must now be combined with 7 , 3 , 9, 8 ,2 > 
                    //so you will get an array of array(1,7) array, (1,3) array (3,9) 
                    //etcetera.. there arrays must be also in a multidimensional array
                   }
                 }
               }
            }

If you have three arrays, wouldn't it be more natural to have an output size of three elements for each result? — Ja͢ck
– Ja͢ck, Commented Jul 2, 2014 at 7:07
Is this just a hypothetical quiz question? Or is there a practical use to this? As it stands, I have little clue on what you are trying to accomplish.. Can you give a practical example ? — Damien Overeem
– Damien Overeem, Commented Jul 2, 2014 at 7:08
ok i will type the example at the end of the question now, just a moment — mister x
– mister x, Commented Jul 2, 2014 at 7:10
what does that mean "availability" for 3 is 2? So maximum two occurrences of 3 per tuple? or per whole set? or what? — Alma Do
– Alma Do, Commented Jul 2, 2014 at 7:48
actually no. Its actually for this.. if the first array has for example 2 arrays: array(1,2) and array(1,3) then the combinations must be 1+1 , 1+3, 2+1, 2+3.. But if the availability of 1 is only 1 then you can't have 1+1 — mister x
– mister x, Commented Jul 2, 2014 at 7:52

Alma Do · Accepted Answer · 2014-07-02 08:08:06Z

1

This issue consists ow two parts. Actually, it can be implemented with one functional block, but that would be hard to read. So, I'll split it to two operations.

Retrieving combinations

First task is to get all combinations. By definition, those combinations are Cartesian product of your array members. That could be produced without recursion, like:

$result = array_reduce(array_slice($input, 1), function($c, $x)
{
   return call_user_func_array('array_merge', 
      array_map(function($y) use ($c)
      {
         return array_map(function($z) use ($y)
         {
            return array_merge((array)$z, (array)$y);
         }, $c);
      }, $x)
   );
}, current($input));

Here we're accumulating our tuples one be one. Result is just all possible combinations as it should be for Cartesian product.

Filtering result

This is another part of the issue. Assuming you have $available as a set of key=>value pairs, where key corresponds to specific number in a tuple and value corresponds to how many times can that number appear in that tuple at most, here's simple filtering code:

$result = array_filter($result, function($tuple) use ($available)
{
   foreach(array_count_values($tuple) as $value=>$count)
   {
      if(isset($available[$value]) && $available[$value]<$count)
      {
         return false;
      }
   }
   return true;
});

For instance, if we have $input as

$input = [
   [1,3],
   [1,6]
];

and restrictions on it as

$available = [6=>0, 1=>1];

Then result would be only

array(1) {
  [1]=>
  array(2) {
    [0]=>
    int(3)
    [1]=>
    int(1)
  }
}

since only this tuple fulfills all requirements (so it has not 6 and 1 appeared once in it)

answered Jul 2, 2014 at 8:08

Alma Do

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13 Comments

mister x Over a year ago

very good explanation. But if available is for example available [1]=>1 and you have array for example like arra(1,2) array(1,3,4,5) array(7,5,6) then there must be these combinations: 1+3, 1+4, 1+5, 1+4, 1+5, 1+6 1+7, and here no 1+1 because there is 1 availability for 1

Alma Do Over a year ago

That's exactly what will happen. So if some combination will have 1 more than once, it will be excluded

mister x Over a year ago

Could you please explain this, because i don't really get what you have done. I try to figure out but very hard tbh

Alma Do Over a year ago

Well, first of - does it work as it's required? If yes, then, I guess, explanation is inside the answer (so we're producing all combinations, then we're filtering them)

Alma Do Over a year ago

Echo? It's an array, so I'm not using "echo" It's var_dump() output

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