public function testLinkedList()
{
$list = new LinkedList();
$this->assertEquals(0, $list->getSize());
$this->assertTrue($list->isEmpty());
$this->assertNull($list->peekFirst());
$this->assertNull($list->peekLast());
$this->assertNull($list->removeFirst());
$this->assertNull($list->removeLast());
$count = 0;
foreach ($list as $key => $value) {
$count++;
}
$this->assertEquals(0, $count);
$list->add("one");
$this->assertEquals(1, $list->getSize());
$this->assertFalse($list->isEmpty());
$list->add("two");
$this->assertEquals(2, $list->getSize());
$this->assertFalse($list->isEmpty());
$list->add("three");
$this->assertEquals(3, $list->getSize());
$this->assertFalse($list->isEmpty());
$expected = ["one", "two", "three"];
$i = 0;
foreach ($list as $key => $value) {
$this->assertEquals($i, $key);
$this->assertEquals($expected[$i], $value);
$i++;
}
$this->assertEquals(3, $i);
$this->assertEquals("one", $list->peekFirst());
$this->assertEquals("one", $list->removeFirst());
$this->assertEquals(2, $list->getSize());
$this->assertEquals("three", $list->peekLast());
$this->assertEquals("three", $list->removeLast());
$this->assertEquals(1, $list->getSize());
$this->assertEquals("two", $list->peekFirst());
$this->assertEquals("two", $list->removeFirst());
$this->assertEquals(0, $list->getSize());
$this->assertTrue($list->isEmpty());
$list->add("four");
$this->assertEquals(1, $list->getSize());
$this->assertFalse($list->isEmpty());
foreach ($list as $key => $value) {
$this->assertEquals(0, $key);
$this->assertEquals("four", $value);
}
$this->assertEquals("four", $list->peekFirst());
$this->assertEquals("four", $list->removeLast());
$this->assertEquals(0, $list->getSize());
$this->assertTrue($list->isEmpty());
}
public static function isPalindrome(LinkedList $list)
{
if ($list->getSize() < 2) {
return true;
}
$first = $list->removeFirst();
$last = $list->removeLast();
if ($first !== $last) {
return false;
}
return self::isPalindrome($list);
}