Serialize and Deserialize the Binary Tree added

Author: Aksshay88

src/test/java/com/thealgorithms/datastructures/trees/SerializeaBinaryTree.java

@@ -0,0 +1,133 @@
+import java.util.*;
+
+// Define the TreeNode class to represent nodes in the binary tree.
+class TreeNode {
+    int val;           // Value stored in the node
+    TreeNode left;     // Pointer to the left child
+    TreeNode right;    // Pointer to the right child
+
+    // Constructor to create a new node with a given value
+    TreeNode(int val) {
+        this.val = val;
+        this.left = null;  // Initially, the left child is null
+        this.right = null; // Initially, the right child is null
+    }
+}
+
+public class BinaryTreeSerializer {
+
+    // The 'serialize' method converts a binary tree into a string.
+    public String serialize(TreeNode root) {
+        // If the tree is empty (root is null), return an empty string.
+        if (root == null) return "";
+
+        // StringBuilder is used to build the final serialized string efficiently.
+        StringBuilder sb = new StringBuilder();
+
+        // We will use a queue to perform level-order traversal (breadth-first search).
+        Queue<TreeNode> queue = new LinkedList<>();
+
+        // Start by adding the root node to the queue.
+        queue.add(root);
+
+        // Process each node in the queue, and append its value (or "null" for empty nodes) to the result.
+        while (!queue.isEmpty()) {
+            // Remove the front node from the queue.
+            TreeNode node = queue.poll();
+
+            // If the node is not null, process its value and add its children to the queue.
+            if (node != null) {
+                // Append the node's value to the string, followed by a comma to separate values.
+                sb.append(node.val).append(",");
+
+                // Add the left and right children to the queue (even if they are null).
+                queue.add(node.left);
+                queue.add(node.right);
+            } else {
+                // If the node is null, append "null" to the string to represent the absence of a node.
+                sb.append("null,");
+            }
+        }
+
+        // Remove the last comma from the end of the string to make it clean.
+        sb.setLength(sb.length() - 1);
+
+        // Return the final serialized string.
+        return sb.toString();
+    }
+
+    // The 'deserialize' method converts a string back into a binary tree.
+    public TreeNode deserialize(String data) {
+        // If the input string is empty, return null (i.e., the tree is empty).
+        if (data == null || data.isEmpty()) return null;
+
+        // Split the string by commas to get the serialized node values.
+        String[] nodes = data.split(",");
+
+        // The first value in the string is the root node.
+        TreeNode root = new TreeNode(Integer.parseInt(nodes[0]));
+
+        // Use a queue to manage the nodes during reconstruction of the tree.
+        Queue<TreeNode> queue = new LinkedList<>();
+        queue.add(root);
+
+        // Use an index to track the current position in the node array (starting from 1, since 0 is root).
+        int index = 1;
+
+        // Process each node in the queue to reconstruct the tree.
+        while (!queue.isEmpty()) {
+            // Get the current node from the queue.
+            TreeNode node = queue.poll();
+
+            // Rebuild the left child.
+            if (!nodes[index].equals("null")) {
+                // If the value is not "null", create a new node and add it to the left.
+                node.left = new TreeNode(Integer.parseInt(nodes[index]));
+                // Add the left child to the queue for further processing.
+                queue.add(node.left);
+            }
+            index++;  // Move to the next value in the array.
+
+            // Rebuild the right child.
+            if (!nodes[index].equals("null")) {
+                // If the value is not "null", create a new node and add it to the right.
+                node.right = new TreeNode(Integer.parseInt(nodes[index]));
+                // Add the right child to the queue for further processing.
+                queue.add(node.right);
+            }
+            index++;  // Move to the next value in the array.
+        }
+
+        // Return the root of the reconstructed tree.
+        return root;
+    }
+
+    public static void main(String[] args) {
+        // Example of creating a binary tree manually.
+        //       1
+        //      / \
+        //     2   3
+        //        / \
+        //       4   5
+
+        TreeNode root = new TreeNode(1);      // Create the root node with value 1
+        root.left = new TreeNode(2);          // Create the left child (value 2)
+        root.right = new TreeNode(3);         // Create the right child (value 3)
+        root.right.left = new TreeNode(4);    // Create the left child of node 3 (value 4)
+        root.right.right = new TreeNode(5);   // Create the right child of node 3 (value 5)
+
+        // Instantiate the BinaryTreeSerializer class
+        BinaryTreeSerializer serializer = new BinaryTreeSerializer();
+
+        // Serialize the tree to a string format
+        String serializedTree = serializer.serialize(root);
+        System.out.println("Serialized Tree: " + serializedTree);
+        // Expected output: "1,2,3,null,null,4,5,null,null,null,null"
+
+        // Deserialize the string back to a binary tree
+        TreeNode deserializedRoot = serializer.deserialize(serializedTree);
+        System.out.println("Tree deserialized successfully. Root value: " + deserializedRoot.val);
+        // Expected output: Root value should be 1
+    }
+}
+