Finding All Permutations of an Array, nPk = n!/(n-k)!:
function pc_permute($items, $perms = array( )) { if (empty($items)) { print join(' ', $perms) . " "; } else { for ($i = count($items) - 1; $i >= 0; --$i) { $newitems = $items; $newperms = $perms; list($foo) = array_splice($newitems, $i, 1); array_unshift($newperms, $foo); pc_permute($newitems, $newperms); } } } $p = pc_permute(array(1, 2, 3, 4)); print join(',', $p) . " "; |