Given a PHP array of strings, e.g.:
['peter', 'paul', 'mary']
How to generate all possible permutations of elements of this array? i.e.:
peter-paul-mary
peter-mary-paul
paul-peter-mary
paul-mary-peter
mary-peter-paul
mary-paul-peter
function pc_permute($items, $perms = array()) {
if (empty($items)) {
echo join(' ', $perms) . "<br />";
} else {
for ($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);
}
}
}
$arr = array('peter', 'paul', 'mary');
pc_permute($arr);
or
function pc_next_permutation($p, $size) {
// slide down the array looking for where we're smaller than the next guy
for ($i = $size - 1; $p[$i] >= $p[$i+1]; --$i) { }
// if this doesn't occur, we've finished our permutations
// the array is reversed: (1, 2, 3, 4) => (4, 3, 2, 1)
if ($i == -1) { return false; }
// slide down the array looking for a bigger number than what we found before
for ($j = $size; $p[$j] <= $p[$i]; --$j) { }
// swap them
$tmp = $p[$i]; $p[$i] = $p[$j]; $p[$j] = $tmp;
// now reverse the elements in between by swapping the ends
for (++$i, $j = $size; $i < $j; ++$i, --$j) {
$tmp = $p[$i]; $p[$i] = $p[$j]; $p[$j] = $tmp;
}
return $p;
}
$set = split(' ', 'she sells seashells'); // like array('she', 'sells', 'seashells')
$size = count($set) - 1;
$perm = range(0, $size);
$j = 0;
do {
foreach ($perm as $i) { $perms[$j][] = $set[$i]; }
} while ($perm = pc_next_permutation($perm, $size) and ++$j);
foreach ($perms as $p) {
print join(' ', $p) . "\n";
}