Get ALL possible results from the mixing array.

Question

I searched everywhere for this online, but could not completely find it. (my PHP and math skills allow me to go down to this ...) I have an array containing, for example, three lines (could also be more!) (For example: "a", "b", "c"). Now I want to create a function that returns ALL possibilities. I searched everywhere and found some good functions that moved the array in every way possible, but they did not delete the value one by one. Thus, they had:

abc acb bac bca cab cba

This is fine, but I need a function that takes it to the next level:

abc acb bac bca cab cba ac ca ab ab ba bc ba abc

and it doesn’t care how many values ​​(say max 10). I struggled with this all evening, maybe someone led me out of my suffering and allowed me this riddle, please? Or give some advice. Thanks

Answer 1

As always, it’s much more interesting to solve the problem in your own way. You can change your code to suit your special needs much easier because you know what you are doing :) See My test script below:

<? $a = array("a", "b", "c"); function getAll($prefix, $remaining) { echo $prefix."\n"; if (count($remaining) == 0) return; if (count($remaining) == 1) { echo $prefix.$remaining[0]."\n"; return; } for ($i = 0; $i < count($remaining); $i++) { $t = $remaining; unset($t[$i]); $t = array_values($t); getAll($prefix.$remaining[$i], $t); } } echo "<pre>\n"; getAll('', $a); echo "</pre>\n"; ?> 

I just chose the expected output, instead you can add an array of results, but this is your part :)

Conclusion:

 [] //empty value is included, but blank lines won't show up here, so I wrote [] a ab abc ac acb b ba bac bc bca c ca cab cb cba 

Answer 2

Sounds like you're asking for a "power set". The power set includes an empty set, which I will not include.

 require_once 'Math/Combinatorics.php'; $set = range('a', 'c'); $permutationSizes = range(1, count($set)); $combinatorics = new Math_Combinatorics; $result = array(); foreach ($permutationSizes as $permutationSize) { $result = array_merge($result, $combinatorics->permutations($set, $permutationSize)); } print_r($result); 

http://pear.php.net/package/Math_Combinatorics

I assume that technically this is not a set of power, because I do order when comparing sets. anyway...

Answer 3

There is an example function for permutations on the O'Reilly PHP Cookbook, section 4.26 . It only creates permutations of a fixed size, but can be used in a loop to work with any size as you need it.

The code

 function pc_next_permutation($p, $size) { // slide down the array looking for where we're smaller than the next guy for ($i = $size - 1; $p[$i] >= $p[$i+1]; --$i) { } // if this doesn't occur, we've finished our permutations // the array is reversed: (1, 2, 3, 4) => (4, 3, 2, 1) if ($i == -1) { return false; } // slide down the array looking for a bigger number than what we found before for ($j = $size; $p[$j] <= $p[$i]; --$j) { } // swap them $tmp = $p[$i]; $p[$i] = $p[$j]; $p[$j] = $tmp; // now reverse the elements in between by swapping the ends for (++$i, $j = $size; $i < $j; ++$i, --$j) { $tmp = $p[$i]; $p[$i] = $p[$j]; $p[$j] = $tmp; } return $p; } $set = explode(' ', 'ab c'); // $all will contain the final output $all = $set; while(count($set) > 1) { $perms = array(); $size = count($set) - 1; $perm = range(0, $size); $j = 0; do { foreach ($perm as $i) { $perms[$j][] = $set[$i]; } } while ($perm = pc_next_permutation($perm, $size) and ++$j); foreach ($perms as $p) { $all[] = implode(' ', $p); } array_pop($set); } // display results foreach($all as $each) { echo $each . "\n"; } 

Exit

 a b c abc acb bac bca cab cba ab ba 

Real time example