several methods added, phpunit extended

src/Algorithm/Search/LinkedListSearch.php

@@ -40,6 +40,7 @@ class LinkedListSearch {
      *
      * @param AbstractLinkedList $linkedList
      * @return bool
+     * @deprecated this method belongs to doganoo\PHPAlgorithms\Common\Abstracts\AbstractLinkedList and is moved there. Please use  this method instead.
      */
     public function hasLoop(AbstractLinkedList $linkedList): bool {
         $tortoise = $linkedList->getHead();
@@ -60,7 +61,7 @@ public function hasLoop(AbstractLinkedList $linkedList): bool {
 
     /**
      * @param AbstractLinkedList $linkedList
-     * @param int                $k
+     * @param int $k
      * @return \doganoo\PHPAlgorithms\Datastructure\Lists\Node|null
      */
     public function findKthElementFromEnd(AbstractLinkedList $linkedList, int $k): ?Node {

src/Common/Abstracts/AbstractLinkedList.php

@@ -26,6 +26,7 @@
 namespace doganoo\PHPAlgorithms\Common\Abstracts;
 
 use doganoo\PHPAlgorithms\Common\Interfaces\IComparable;
+use doganoo\PHPAlgorithms\Common\Interfaces\IUnaryNode;
 use doganoo\PHPAlgorithms\Common\Util\Comparator;
 use doganoo\PHPAlgorithms\Datastructure\Lists\Node;
 
@@ -492,6 +493,50 @@ public function compareTo($object): int {
         return -1;
     }
 
+    /**
+     * also known as the Runner Technique
+     *
+     * @return bool
+     */
+    public function hasLoop(): bool {
+        $tortoise = $this->getHead();
+        $hare = $this->getHead();
+
+        while ($tortoise !== null && $hare->getNext() !== null) {
+            $hare = $hare->getNext()->getNext();
+
+            if (Comparator::equals($tortoise->getValue(), $hare->getValue())) {
+                return true;
+            }
+
+            $tortoise = $tortoise->getNext();
+        }
+        return false;
+    }
+
+    /**
+     * returns the middle node of the linked list
+     *
+     * @return IUnaryNode|null
+     */
+    public function getMiddleNode(): ?IUnaryNode {
+        $head = $this->getHead();
+
+        if (null === $head) return null;
+
+        $p = $head;
+        $q = $head;
+
+        while (null !== $p &&
+            null !== $q && //actually not really necessary since $p and $q point to the same object
+            null !== $q->getNext()
+        ) {
+            $p = $p->getNext();
+            $q = $q->getNext()->getNext();
+        }
+        return $p;
+    }
+
     /**
      * Specify data which should be serialized to JSON
      *
@@ -506,6 +551,7 @@ public function jsonSerialize() {
         ];
     }
 
+    //TODO implement
     //protected function removeDuplicates() {
     //    $node = $this->head;
     //    $previous = $this->head;

src/Datastructure/Graph/Tree/Heap/MaxHeap.php

@@ -191,4 +191,13 @@ public function jsonSerialize() {
             , "type" => "MAX_HEAP",
         ];
     }
+
+    /**
+     * returns the heap as an array
+     *
+     * @return array|null
+     */
+    public function getHeap(): ?array {
+        return $this->heap;
+    }
 }

src/Datastructure/Graph/Tree/Heap/MinHeap.php

@@ -191,4 +191,13 @@ public function jsonSerialize() {
             , "type" => "MIN_HEAP",
         ];
     }
+
+    /**
+     * returns the heap as an array
+     *
+     * @return array|null
+     */
+    public function getHeap(): ?array {
+        return $this->heap;
+    }
 }

tests/Lists/LinkedLists/DoublyLinkedListTest.php

@@ -214,4 +214,25 @@ public function testRemoveAndReplace() {
         $node = $list->getNodeByKey(3);
         $this->assertTrue($replaced && $node instanceof Node);
     }
+
+    /**
+     * tests whether the singly linked list has a loop or not
+     */
+    public function testHasLoop() {
+        $list = LinkedListUtil::getDoublyLinkedList();
+        $this->assertTrue(false === $list->hasLoop());
+        $list = LinkedListUtil::getDoublyLinkedListWithLoop();
+        $this->assertTrue(true === $list->hasLoop());
+    }
+
+    public function testMiddlePart() {
+        $ll = LinkedListUtil::getCustomDoublyLinkedList(5);
+        /** @var Node $node */
+        $node = $ll->getMiddleNode();
+
+        print_r($node->getKey());
+        ob_flush();
+        $this->assertTrue(3 === $node->getKey());
+        $this->assertTrue(md5(3) === $node->getValue());
+    }
 }

tests/Util/LinkedListUtil.php

@@ -51,6 +51,20 @@ public static function getDoublyLinkedList(): DoublyLinkedList {
         return $list;
     }
 
+    /**
+     * returns a doubly linked list with $n elements
+     *
+     * @param int $n the number of elements
+     * @return DoublyLinkedList
+     */
+    public static function getCustomDoublyLinkedList(int $n): DoublyLinkedList {
+        $list = new DoublyLinkedList();
+        for ($i = 0; $i < $n; $i++) {
+            $list->add($i + 1, md5($i + 1));
+        }
+        return $list;
+    }
+
     /**
      * returns a singly linked list containing three elements
      *
@@ -64,6 +78,28 @@ public static function getSinglyLinkedList(): SinglyLinkedList {
         return $list;
     }
 
+    /**
+     * returns a singly linked list containing three elements with a loop
+     *
+     * @return DoublyLinkedList
+     */
+    public static function getDoublyLinkedListWithLoop(): DoublyLinkedList {
+        $list = new DoublyLinkedList();
+        $one = LinkedListUtil::getNode(1, "one");
+        $two = LinkedListUtil::getNode(1, 2);
+        $three = LinkedListUtil::getNode(1, new stdClass());
+
+        $one->setNext($two);
+        $one->setPrevious(null);
+        $two->setNext($three);
+        $two->setPrevious($one);
+        $three->setNext($one);
+        $three->setPrevious($two);
+
+        $list->setHead($one);
+        return $list;
+    }
+
     /**
      * creates a node instance with the given parameters
      *