, (*1)
String combinations
A simple, low-memory footprint function to generate all string combinations from a series of characters., (*2)
Installation
PHP 7.4+ is required., (*3)
composer require bentools/string-combinations, (*4)
Usage
I want to get all combinations with the letters a, b, c., (*5)
require_once __DIR__ . '/vendor/autoload.php';
use function BenTools\StringCombinations\string_combinations;
foreach (string_combinations('abc') as $combination) { // Can also be string_combinations(['a', 'b', 'c'])
echo $combination . PHP_EOL;
}
Output:, (*6)
a
b
c
aa
ab
ac
ba
bb
bc
ca
cb
cc
aaa
aab
aac
aba
abb
abc
aca
acb
acc
baa
bab
bac
bba
bbb
bbc
bca
bcb
bcc
caa
cab
cac
cba
cbb
cbc
cca
ccb
ccc
Array output, (*7)
It will dump all combinations into an array., (*8)
var_dump(string_combinations('abc')->asArray());
Count combinations, (*9)
It will return the number of possible combinations., (*10)
var_dump(count(string_combinations('abc'))); // 39
Specifying min length, max length, (*11)
foreach (string_combinations('abc', $min = 2, $max = 2) as $combination) {
echo $combination . PHP_EOL;
}
Output:, (*12)
aa
ab
ac
ba
bb
bc
ca
cb
cc
Using an array as first argument, and a separator, (*13)
foreach (string_combinations(['woof', 'meow', 'roar'], 2, 3, '-') as $combination) {
echo $combination . PHP_EOL;
}
Output:, (*14)
woof-woof
woof-meow
woof-roar
meow-woof
meow-meow
meow-roar
roar-woof
roar-meow
roar-roar
woof-woof-woof
woof-woof-meow
woof-woof-roar
woof-meow-woof
woof-meow-meow
woof-meow-roar
woof-roar-woof
woof-roar-meow
woof-roar-roar
meow-woof-woof
meow-woof-meow
meow-woof-roar
meow-meow-woof
meow-meow-meow
meow-meow-roar
meow-roar-woof
meow-roar-meow
meow-roar-roar
roar-woof-woof
roar-woof-meow
roar-woof-roar
roar-meow-woof
roar-meow-meow
roar-meow-roar
roar-roar-woof
roar-roar-meow
roar-roar-roar
No duplicates, (*15)
You can avoid generating stings having the same letter more than once with the withoutDuplicates() method:, (*16)
$combinations = string_combinations('abc');
var_dump(count($combinations)); // 39
print_r($combinations->asArray());
Array
(
[0] => a
[1] => b
[2] => c
[3] => aa
[4] => ab
[5] => ac
[6] => ba
[7] => bb
[8] => bc
[9] => ca
[10] => cb
[11] => cc
[12] => aaa
[13] => aab
[14] => aac
[15] => aba
[16] => abb
[17] => abc
[18] => aca
[19] => acb
[20] => acc
[21] => baa
[22] => bab
[23] => bac
[24] => bba
[25] => bbb
[26] => bbc
[27] => bca
[28] => bcb
[29] => bcc
[30] => caa
[31] => cab
[32] => cac
[33] => cba
[34] => cbb
[35] => cbc
[36] => cca
[37] => ccb
[38] => ccc
), (*17)
$combinations = $combinations->withoutDuplicates();
var_dump(count($combinations)); // 15
print_r($combinations->asArray());
Array
(
[0] => a
[1] => b
[2] => c
[3] => ab
[4] => ac
[5] => ba
[6] => bc
[7] => ca
[8] => cb
[9] => abc
[10] => acb
[11] => bac
[12] => bca
[13] => cab
[14] => cba
), (*18)
Because it uses Generators to generate all possible combinations, you can iterate over thousands of possibilities without losing a single MB., (*19)
This has been executed on my Core i7 personnal computer with 8GB RAM:, (*20)
require_once __DIR__ . '/vendor/autoload.php';
use function BenTools\StringCombinations\string_combinations;
$start = microtime(true);
$combinations = string_combinations('abcd1234');
foreach ($combinations as $c => $combination) {
continue;
}
$end = microtime(true);
printf(
'Generated %d combinations in %ss - Memory usage: %sMB / Peak usage: %sMB' . PHP_EOL,
++$c,
round($end - $start, 3),
round(memory_get_usage(true) / 1024 / 1024),
round(memory_get_peak_usage(true) / 1024 / 1024)
);
Output:, (*21)
Generated 19173960 combinations in 5.579s - Memory usage: 2MB / Peak usage: 2MB, (*22)
Tests
./vendor/bin/phpunit, (*23)
See also
Wallogit.com
