<?php


$arbre = array ( 1, 2, 4, 1);
affichage($arbre);


/**
 * @param int $i
 *
 * @return table
 **/
function get (int $i)
{
    if($i === 1){
        return ['A', 'B', 'C'];
    }
    if($i === 2){
        return ['D', 'E', 'F'];
    }
    if($i === 3){
        return ['G', 'H', 'I'];
    }
    if($i === 4){
        return ['J', 'K', 'L'];
    }
    if($i === 5){
        return ['M', 'N', 'O'];
    }
    if($i === 6){
        return ['P', 'Q', 'R'];
    }
    if($i === 7){
        return ['S', 'T', 'U'];
    }
    if($i === 8){
        return ['V', 'W', 'X'];
    }
    if($i === 9){
        return ['Y', 'Z', '€'];
    }
}

/**
 * @param array $list
 *
 * @return array
 **/
function solve (array $list)
{
    if (count($list) === 0) {
        return [];
    }

    if (count($list) === 1) {
        return $list[0];
    }

    $newList = [ addArray($list[0], $list[1]) ];

    if (count($list) === 2) {
        return $newList[0];
    }

    foreach ($list as $key => $value) {
        if ($key === 0 || $key === 1) {
            continue;
        }

        $newList[] = $value;
    }

    return solve($newList);
}

/**
 * @param array $list
 * @param array $elements
 *
 * @return array
 **/
function addArray (array $list, array $elements)
{
    $newList = [];

    foreach ($list as $value) {
        foreach ($elements as $element) {
            $newList[] = $value.$element;
        }
    }

    return $newList;
}

/**
 * @param array $list
 *
 * @return array
 **/
function getGet (array $list)
{
    $newList = [];

    foreach ($list as $value) {
        array_push ($newList, get($value));
    }

    return $newList;
}

/**
 * @param array $ab
 **/
function affichage (array $ab)
{
    foreach (solve(getGet($ab)) as $value) {print ($value); print "\n";}
}