PHP Array: join each sub-array together (Probability)

Question

I want simply to find-out better way to do this:

$array = array(
    array(\'a\', \'b\', \'c\'),
    array(\'e\', \'f\', \'g\'),
    array(\'h\', \'i\', \'j\'         


        

Answer 1

I'm impressed about the great algorithms you guys came up with. However i think that the right method in PHP, is to use an Iterator: http://php.net/manual/fr/class.iterator.php

I implemented an example of what you could do for your problem.

class CombinationIterator implements Iterator {
    private $position = 0;
    private $array = array();

    public function __construct($array) {
        $this->array = $array;
        $this->position = array_fill(0,sizeof($this->array),0);
    }

    function rewind() {
        $this->position = array_fill(0,sizeof($this->array),0);
    }

    function current() {
        $word = array();
        foreach ($this->position as $i=>$pos) {
            $word[]=$this->array[$i][$pos];
        }
        return implode(" ",$word);
    }

    function key() {
        return $this->position;
    }
    function next() {
        foreach (array_reverse($this->position,true) as $i=>$pos) {
            # if position in this array has reached end, set it to 0 and increse next one
            if ($pos == sizeof($this->array[$i])-1) {
                $this->position[$i] = 0;
                if (array_key_exists($i-1,$this->position)) {
                    continue;
                } else {
                    $this->rewind();
                }
                break;
            } else {
                $this->position[$i]++;
                break;
            }

        }
    }
    function valid() {
        $valid = false;
        foreach ($this->position as $i=>$pos) {
            if ($pos < sizeof($this->array[$i])-1) { return true; }
        }
        return $valid;
    }

}

And here is how you could use it to display your words :

$array = array(
    array('a', 'b', 'c'),
    array('e', 'f', 'g'),
    array('h', 'i', 'j', 'k', 'l'),
    array('m', 'n', 'o', 'p', 'q', 'r', 's'),
    array('t', 'u', 'v', 'x', 'y', 'z')
);


$c = new CombinationIterator($array);
while ($c->valid()) {
    echo $c->current()."\n";
    $c->next();
}

I didn't write the previous() method, but you can easily create it from the next() method.

Also memory usage is very low here because you only get the position stored.

I hope it can help you for your project.

Bye