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run code in 300+ PHP versions simultaneously
<?php $str = 'ABC1'; permute(str_split($str), 0, strlen($str)); function permute($arr, $i, $n) { if ($i == $n) { printArray($arr); return; } for ($j = $i; $j <= $n; $j += 1) { swapArrayValues($arr, $i, $j); permute($arr, $i + 1, $n); swapArrayValues($arr, $i, $j); } } function swapArrayValues(&$array, $i, $j) { $tmp = $array[$i]; $array[$i] = $array[$j]; $array[$j] = $tmp; } function printArray($arr) { echo implode($arr, ' ') . "\n"; }

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36.66 ms | 402 KiB | 5 Q