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@ehsanhoushmand
Last active September 12, 2021 12:59
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php algorithm to generate all combinations of a specific size from a single set
function sampling($chars, $size, $combinations = array()) {
# if it's the first iteration, the first set
# of combinations is the same as the set of characters
if (empty($combinations)) {
$combinations = $chars;
}
# we're done if we're at size 1
if ($size == 1) {
return $combinations;
}
# initialise array to put new values in
$new_combinations = array();
# loop through existing combinations and character set to create strings
foreach ($combinations as $combination) {
foreach ($chars as $char) {
$new_combinations[] = $combination . $char;
}
}
# call same function again for the next iteration
return sampling($chars, $size - 1, $new_combinations);
}
// example
$chars = array('a', 'b', 'c');
$output = sampling($chars, 2);
var_dump($output);
/*
array(9) {
[0]=>
string(2) "aa"
[1]=>
string(2) "ab"
[2]=>
string(2) "ac"
[3]=>
string(2) "ba"
[4]=>
string(2) "bb"
[5]=>
string(2) "bc"
[6]=>
string(2) "ca"
[7]=>
string(2) "cb"
[8]=>
string(2) "cc"
}
*/
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