finding all possible combinations from a given number

Question

How can I find all possible combinations from a given 3 digit number using PHP? for example if the number is 123, the possible array results should be following

123,132,213,321,321,312

and when a number repeats, there should be no duplicates. example

$threedigit="001";

result should be

001,010,100

there is more possible numbers.

How I achieve this using PHP ?

Answer 1

This would be an example of a simple solution for a fixed length of 3 digits:

<?php
function permutations($input) {
  $digit = str_split($input, 1);
  $output = [];
  for ($i=0; $i<3; $i++) {
    for ($j=0; $j<3; $j++) {
      if ($i==$j) continue;
      for ($k=0; $k<3; $k++) {
        if ($i==$k || $j==$k) continue;
        $output[] = $digit[$i] . $digit[$j] . $digit[$k];
      }
    }
  }
  return array_unique($output);
}
print_r(permutations("123"));
print_r(permutations("001"));

The obvious output contains first 6, second 3 entries:

Array
(
    [0] => 123
    [1] => 132
    [2] => 213
    [3] => 231
    [4] => 312
    [5] => 321
)
Array
(
    [0] => 001
    [1] => 010
    [4] => 100
)