Implemented AVL Tree Data Structure. Added serialization/deserializat…

…ion feature. Added corresponding unit test.
Ramy-Badr-Ahmed · Oct 12, 2024 · e145894 · e145894
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diff --git a/DataStructures/AVLTree/AVLTree.php b/DataStructures/AVLTree/AVLTree.php
@@ -1,8 +1,9 @@
 <?php
 
 /*
- * Created by: Ramy-Badr-Ahmed (https://github.com/Ramy-Badr-Ahmed) in Pull Request: #163
- * https://github.com/TheAlgorithms/PHP/pull/163
+ * Created by: Ramy-Badr-Ahmed (https://github.com/Ramy-Badr-Ahmed)
+ * in Pull Request #163: https://github.com/TheAlgorithms/PHP/pull/163
+ * and #173: https://github.com/TheAlgorithms/PHP/pull/173
  *
  * Please mention me (@Ramy-Badr-Ahmed) in any issue or pull request addressing bugs/corrections to this file.
  * Thank you!
@@ -311,4 +312,81 @@ private function getMinNode(AVLTreeNode $node): AVLTreeNode
         }
         return $node;
     }
+
+    /**
+     * Serializes the segment tree into a JSON string.
+     *
+     * @return string The serialized AVL Tree as a JSON string.
+     */
+    public function serialize(): string
+    {
+        return json_encode($this->serializeTree($this->root));
+    }
+
+    /**
+     * Recursively serializes the AVL Tree.
+     *
+     * @param AVLTreeNode|null $node
+     * @return array
+     */
+    private function serializeTree(?AVLTreeNode $node): array
+    {
+        if ($node === null) {
+            return [];
+        }
+        return [
+            'key' => $node->key,
+            'value' => $node->value,
+            'left' => $this->serializeTree($node->left),
+            'right' => $this->serializeTree($node->right),
+            'height' => $node->height,
+        ];
+    }
+
+    /**
+     * Deserializes a JSON string into an AVL Tree object
+     *
+     * @param string $data The JSON representation of an AVL Tree to deserialize.
+     */
+    public function deserialize(string $data): void
+    {
+        $this->root = $this->deserializeTree(json_decode($data, true));
+        $this->counter = 0;
+        $this->updateNodeCount($this->root);
+    }
+
+    /**
+     * Recursively deserializes an AVL Tree from an array representation.
+     *
+     * @param array $data The serialized data for the node.
+     * @return AVLTreeNode|null The root node of the deserialized tree.
+     */
+    private function deserializeTree(array $data): ?AVLTreeNode
+    {
+        if (empty($data)) {
+            return null;
+        }
+
+        $node = new AVLTreeNode($data['key'], $data['value']);
+        $node->height = $data['height'];
+
+        $node->left = $this->deserializeTree($data['left']);
+        $node->right = $this->deserializeTree($data['right']);
+
+        return $node;
+    }
+
+    /**
+     * Updates the deserialized tree size.
+     *
+     * @param AVLTreeNode|null $node The root node of the deserialized tree.
+     */
+    private function updateNodeCount(?AVLTreeNode $node): void
+    {
+        if ($node !== null) {
+            $this->counter++;
+            $this->updateNodeCount($node->left);
+            $this->updateNodeCount($node->right);
+        }
+    }
 }
diff --git a/tests/DataStructures/AVLTreeTest.php b/tests/DataStructures/AVLTreeTest.php
@@ -1,8 +1,9 @@
 <?php
 
 /*
- * Created by: Ramy-Badr-Ahmed (https://github.com/Ramy-Badr-Ahmed) in Pull Request: #163
- * https://github.com/TheAlgorithms/PHP/pull/163
+ * Created by: Ramy-Badr-Ahmed (https://github.com/Ramy-Badr-Ahmed)
+ * in Pull Request #163: https://github.com/TheAlgorithms/PHP/pull/163
+ * and #173: https://github.com/TheAlgorithms/PHP/pull/173
  *
  * Please mention me (@Ramy-Badr-Ahmed) in any issue or pull request addressing bugs/corrections to this file.
  * Thank you!
@@ -37,6 +38,9 @@ private function populateTree(): void
         $this->tree->insert(15, 'Value 15');
     }
 
+    /**
+     * Tests the insert and search operations in the AVLTree.
+     */
     public function testInsertAndSearch(): void
     {
         $this->populateTree();
@@ -47,6 +51,10 @@ public function testInsertAndSearch(): void
         $this->assertNull($this->tree->search(25), 'Value for non-existent key 25 should be null');
     }
 
+    /**
+     * Tests the deletion of nodes and ensures the AVLTree maintains
+     * its integrity after deletions.
+     */
     public function testDelete(): void
     {
         $this->populateTree();
@@ -167,6 +175,9 @@ public function testInsertDuplicateKeys(): void
         );
     }
 
+    /**
+     * Tests the insertion and deletion of a large number of nodes.
+     */
     public function testLargeTree(): void
     {
         // Inserting a large number of nodes
@@ -186,6 +197,9 @@ public function testLargeTree(): void
         }
     }
 
+    /**
+     * Tests whether the AVLTree remains balanced after insertions.
+     */
     public function testBalance(): void
     {
         $this->populateTree();
@@ -300,4 +314,53 @@ public function testSizeOnEmptyTree(): void
         $this->tree = new AVLTree();
         $this->assertEquals(0, $this->tree->size(), 'Size should be 0 for an empty tree');
     }
+
+    /**
+     * Test serialization and deserialization
+     */
+    public function testAVLTreeSerialization(): void
+    {
+        $avlTree = new AVLTree();
+
+        $avlTree->insert(100, 'Value 100');
+        $avlTree->insert(200, 'Value 200');
+        $avlTree->insert(50, 'Value 50');
+        $avlTree->insert(150, 'Value 150');
+        $avlTree->insert(350, 'Value 350');
+        $avlTree->insert(40, 'Value 40');
+        $avlTree->insert(90, 'Value 90');
+
+        $avlTreeRoot = $avlTree->getRoot();
+        $serializedAVLTree = $avlTree->serialize();
+
+        $deserializedTree = new AVLTree();
+        $deserializedTree->deserialize($serializedAVLTree);
+
+        $deserializedTreeRoot = $deserializedTree->getRoot();
+
+        $this->assertEquals($deserializedTreeRoot->key, $avlTreeRoot->key, 'The two roots key should match');
+        $this->assertEquals($deserializedTreeRoot->value, $avlTreeRoot->value, 'The two roots value should match');
+        $this->assertEquals(
+            $deserializedTreeRoot->left->key,
+            $avlTreeRoot->left->key,
+            'Left child of the two roots should match'
+        );
+        $this->assertEquals(
+            $deserializedTreeRoot->right->key,
+            $avlTreeRoot->right->key,
+            'Left child of the two roots should match'
+        );
+        $this->assertEquals(
+            $deserializedTreeRoot->height,
+            $avlTreeRoot->height,
+            'The two trees should match in height'
+        );
+        $this->assertEquals($deserializedTree->size(), $avlTree->size(), 'The two trees should match in size');
+
+        $this->assertSame(
+            $deserializedTree->inOrderTraversal(),
+            $avlTree->inOrderTraversal(),
+            'Tree structure was not retained'
+        );
+    }
 }