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, Feb 14 '12 at 00:39
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](http://en.wikipedia.org/wiki/Cartesian_product) using them all, you do want *nested* loops. — JYelton, Feb 14 '12 at 00:55
possible duplicate of [Finding cartesian product with PHP associative arrays](http://stackoverflow.com/questions/6311779/finding-cartesian-product-with-php-associative-arrays) — deceze, Feb 14 '12 at 01:04
Well its not necessarily just 3 foreach's needed. The above can have any number of extra elements — wonza, Feb 14 '12 at 01:08
Just had a chance try out the cartesian function you mentioned, that worked perfectly thanks! — wonza, Feb 14 '12 at 02:07

redShadow · Accepted Answer · 2012-02-14T01:47:14.370

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..

Oh, and just fyi, in Python you would do this: http://stackoverflow.com/questions/533905/get-the-cartesian-product-of-a-series-of-lists-in-python :) — redShadow, Feb 14 '12 at 01:41

score 1 · Answer 2 · answered Feb 14 '12 at 00:52

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 — Ananda, Sep 18 '15 at 11:24

score 0 · Answer 3 · answered Feb 14 '12 at 00:51

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 '12 at 00:51

nickb

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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 – wonza Feb 14 '12 at 01:15
Oh, my mistake. Your title is misleading, as it specifically says 3 arrays. – nickb Feb 14 '12 at 01:20

Get all combinations from multiple nested arrays

3 Answers3