Get all combinations from multiple nested arrays

Question

I'm trying to come up with an algorithm in PHP to get all the combinations for a nested array:

Array
(
    [0] => Array
        (
            [0] => Option Object
                (
                    [strValue] => rough
                )

            [1] => Option Object
                (
                    [strValue] => smooth
                )

            [2] => Option Object
                (
                    [strValue] => coarse
                )

        )

    [1] => Array
        (
            [0] => Option Object
                (
                    [strValue] => shiney
                )

            [1] => Option Object
                (
                    [strValue] => mat
                )

        )

    [2] => Array
        (
            [0] => Option Object
                (
                    [strValue] => Large
                )

            [1] => Option Object
                (
                    [strValue] => Medium
                )

            [2] => Option Object
                (
                    [strValue] => Small
                )

            [3] => Option Object
                (
                    [strValue] => very large
                )

        )

)

So I would get something back like:

-rough, shiney, Large

-rough, shiney, Small

-rough, shiney, Medium

-rough, shiney, Very Large

-smooth, shiney, Large

-smooth, shiney, Small

-smooth, shiney, Medium

-smooth, shiney, Very Large

etc (should be 24 in this example)

I've tried through various foreach examples and some basic recursive function, but I seem to be getting no where fast. If anyone could give a basic outline of how to solve this I'd be very grateful, thanks!

and how exactly is your code (which would ideally be added to the question) failing? Because at first sight a set of 3 nested for loops should be all that's needed to solve your problem. — fvu
– fvu, Commented Feb 14, 2012 at 0:39
I wouldn't say the arrays are nested, necessarily. They are all contained in a parent array, but they aren't nested with respect to each other. But to create a cartesian product using them all, you do want nested loops. — JYelton
– JYelton, Commented Feb 14, 2012 at 0:55
possible duplicate of Finding cartesian product with PHP associative arrays — deceze
– deceze ♦, Commented Feb 14, 2012 at 1:04
Well its not necessarily just 3 foreach's needed. The above can have any number of extra elements — wonza
– wonza, Commented Feb 14, 2012 at 1:08
Just had a chance try out the cartesian function you mentioned, that worked perfectly thanks! — wonza
– wonza, Commented Feb 14, 2012 at 2:07

redShadow · Accepted Answer · 2012-02-14 01:47:14Z

9

I just wrote this, that works for arrays of any length..

<?php

function cartesian_product($a) {
  $result = array(array());
  foreach ($a as $list) {
    $_tmp = array();
    foreach ($result as $result_item) {
      foreach ($list as $list_item) {
        $_tmp[] = array_merge($result_item, array($list_item));
      }
    }
    $result = $_tmp;
  }
  return $result;
}


// Let's test this..                                                                                                                                                                                    

header('Content-type: text/plain');

$a = array(
  array('rough','smooth','coarse'),
  array('shiney','mat'),
  array('small','medium','large','x-large'),
);

$result = cartesian_product($a);
foreach ($result as $row) {
  print implode(", ", $row) ."\n";
}

edit: Improved the code a bit..

edited Feb 14, 2012 at 1:47

answered Feb 14, 2012 at 1:39

redShadow

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1 Comment

redShadow Over a year ago

Oh, and just fyi, in Python you would do this: stackoverflow.com/questions/533905/… :)

JYelton · Accepted Answer · 2012-02-14 00:52:59Z

Time to nest some foreach loops!

<?php
$array1 = array('rough', 'smooth', 'coarse');
$array2 = array('shiny', 'matte');
$array3 = array('very large', 'large', 'medium', 'small');

foreach($array1 as $i)
    foreach($array2 as $j)
        foreach($array3 as $k)
            $output[] = "$i, $j, $k";

var_dump($output);
/* ouput
array
  0 => string 'rough, shiny, very large' (length=24)
  1 => string 'rough, shiny, large' (length=19)
  2 => string 'rough, shiny, medium' (length=20)
  3 => string 'rough, shiny, small' (length=19)
  4 => string 'rough, matte, very large' (length=24)
  5 => string 'rough, matte, large' (length=19)
  6 => string 'rough, matte, medium' (length=20)
  7 => string 'rough, matte, small' (length=19)
  8 => string 'smooth, shiny, very large' (length=25)
  9 => string 'smooth, shiny, large' (length=20)
  10 => string 'smooth, shiny, medium' (length=21)
  11 => string 'smooth, shiny, small' (length=20)
  12 => string 'smooth, matte, very large' (length=25)
  13 => string 'smooth, matte, large' (length=20)
  14 => string 'smooth, matte, medium' (length=21)
  15 => string 'smooth, matte, small' (length=20)
  16 => string 'coarse, shiny, very large' (length=25)
  17 => string 'coarse, shiny, large' (length=20)
  18 => string 'coarse, shiny, medium' (length=21)
  19 => string 'coarse, shiny, small' (length=20)
  20 => string 'coarse, matte, very large' (length=25)
  21 => string 'coarse, matte, large' (length=20)
  22 => string 'coarse, matte, medium' (length=21)
  23 => string 'coarse, matte, small' (length=20)
*/
?>

thanks for providing the output that made the reply easy to validate

nickb · Accepted Answer · 2012-02-14 00:51:47Z

0

Here is the brute force (worst efficiency) algorithm in psuedo-PHP:

$array1 = $array[0];
$array2 = $array[1];
$array3 = $array[2];

$results = array();
for( $i = 0; $i < count( $array1); $i++)
    for( $j = 0; $j < count( $array2); $j++)
        for( $k = 0; $k < count( $array3); $k++)
            $results[] = $array1[$i] . ',' . $array2[$j] . ',' . $array3[$k];

answered Feb 14, 2012 at 0:51

nickb

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2 Comments

wonza Over a year ago

As I just commented above, its not necessarily just 3 foreach's needed. The above can have any number of extra elements, this is dynamic, so I can't just limit it to 3 nested for/foreach

nickb Over a year ago

Oh, my mistake. Your title is misleading, as it specifically says 3 arrays.

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