Every possible combination of a string in php

Question

I need to build strings in PHP with every possible combination like

s5z-s4z-s3z-s2z-s1z

where the 's' then the number are always in the same position. the only difference is whether there is a z on the end or not.

So for example I would have

s5z-s4z-s3z-s2z-s1
s5z-s4z-s3z-s2z-s1z
s5z-s4z-s3z-s2-s1
s5z-s4z-s3z-s2z-s1
s5z-s4z-s3z-s2-s1z
s5z-s4z-s3-s2-s1z
etc.

How would I go about doing that?

Please re-tag your question as "homework". Also, it's a dup of: http://stackoverflow.com/questions/2617055/how-to-generate-all-permutations-of-a-string-in-php — Nir Alfasi, Sep 06 '12 at 20:52
@MoeTsao I guess the OP doesn't understand that he won't have access to SO during the final exam... :) — Nir Alfasi, Sep 06 '12 at 20:56
@alfasin What if he does? Should we setup a "test_question" tag? Advise all school teachers to monitor this during programming language test? We can then tag it with the community's force — Moe Tsao, Sep 06 '12 at 21:00

score 3 · Answer 1 · answered Sep 06 '12 at 20:51

So basically it all relies on "is the z there or not". This can easily be translated to a binary number, where each 0 represents the z not being there, and each 1 indicated the presence of the z.

As a result, you need only loop through all the numbers.

$length = 5;
$max = bindec(str_repeat("1",$length));
$out = Array();
for( $i=0; $i<$max; $i++) {
  $entry = Array();
  for( $x=0; $x<$length; $x++) $entry[] = "s".($length-$x).($i & (1<<$x) ? "z" : "");
  $out[] = implode("-",$entry);
}
echo implode(" ",$out);

Thanks! I tried all sorts of things and could not get it. thank you very much for this. — Blade, Sep 06 '12 at 23:58

Every possible combination of a string in php

1 Answers1