Print the middle nodes of each level of a binary tree

Here given code implementation process.

import java.util.ArrayList;
// Java program for
// Print the middle nodes of each level of a binary tree

// Binary Tree node
class TreeNode
{
	public int data;
	public TreeNode left;
	public TreeNode right;
	public TreeNode(int data)
	{
		// Set node value
		this.data = data;
		this.left = null;
		this.right = null;
	}
}
// Queue Node
class QNode
{
	public TreeNode n;
	public QNode next;
	public QNode(TreeNode n)
	{
		this.n = n;
		this.next = null;
	}
}
//Define custom queue class
class MyQueue
{
	public QNode front;
	public QNode rear;
	public int size;
	public MyQueue()
	{
		this.front = null;
		this.rear = null;
		this.size = 0;
	}
	// Add a new node at last of queue
	public void enqueue(TreeNode n)
	{
		QNode node = new QNode(n);
		if (this.front == null)
		{
			// When first node of queue
			this.front = node;
		}
		else
		{
			// Add node at last level
			this.rear.next = node;
		}
		this.size++;
		this.rear = node;
	}
	// Delete front node of queue
	public void dequeue()
	{
		if (this.front != null)
		{
			if (this.rear == this.front)
			{
				this.rear = null;
				this.front = null;
			}
			else
			{
				this.front = this.front.next;
			}
			this.size--;
		}
	}
	public int isSize()
	{
		return this.size;
	}
	public boolean isEmpty()
	{
		if (this.isSize() == 0)
		{
			return true;
		}
		return false;
	}
	public TreeNode peek()
	{
		if (this.isSize() == 0)
		{
			return null;
		}
		else
		{
			return this.front.n;
		}
	}
}
// Define Binary Tree 
public class BinaryTree
{
	public TreeNode root;
	public BinaryTree()
	{
		this.root = null;
	}
	// Print the middle element of given level
	public void printMiddleNode(ArrayList < Integer > level)
	{
		if (level.size() > 0)
		{
			int middle = level.size() / 2;
			if ((level.size() % 2) == 0)
			{
				// When two middle element possible
				System.out.print("\n " + level.get(middle - 1));
				System.out.print(" " + level.get(middle));
			}
			else
			{
				System.out.print("\n " + level.get(middle));
			}
		}
	}
	// This is display middle node of each level in binary tree
	public void middleLevelNode()
	{
		if (this.root == null)
		{
			// When tree is empty
			return;
		}
		// Auxiliary queue which is capable to contain a tree level nodes
		MyQueue q1 = new MyQueue();
		MyQueue q2 = new MyQueue();
		// Auxiliary temp variable
		TreeNode temp = null;
		int level = 1;
		// It will be use assemble a level node.
		ArrayList < Integer > record = new ArrayList < Integer > ();
		// Add first node in q1
		q1.enqueue(this.root);
		// This loop execute until auxiliary queue q1 and q2 are not empty
		while (!q1.isEmpty() || !q2.isEmpty())
		{
			// Execute loop until q1 queue are not empty
			// And store the next level node in q2 queue
			while (!q1.isEmpty())
			{
				// Get top node of q1 queue
				temp = q1.peek();
				// Add node value
				record.add(temp.data);
				if (temp.left != null)
				{
					q2.enqueue(temp.left);
				}
				if (temp.right != null)
				{
					q2.enqueue(temp.right);
				}
				// Remove top element of q1 queue
				q1.dequeue();
			}
			printMiddleNode(record);
			record.clear();
			level++;
			// Execute loop until q2 queue are not empty
			// And store the next level node in q1 queue
			while (!q2.isEmpty())
			{
				// Get top node of q2 queue
				temp = q2.peek();
				// Add node value
				record.add(temp.data);
				if (temp.left != null)
				{
					q1.enqueue(temp.left);
				}
				if (temp.right != null)
				{
					q1.enqueue(temp.right);
				}
				// Remove top element of q2 queue
				q2.dequeue();
			}
			printMiddleNode(record);
			record.clear();
			level++;
		}
	}
	public static void main(String[] args)
	{
		BinaryTree tree = new BinaryTree();
		/*
		    Create Binary Tree
		    -----------------
		         -6                            
		       /   \    
		      4    -7    
		     / \     \               
		    2   3     12
		       / \   /  \
		      10 -4 5    9
		     /     \      \
		    1      7      8

		*/
		tree.root = new TreeNode(-6);
		tree.root.left = new TreeNode(4);
		tree.root.left.right = new TreeNode(3);
		tree.root.left.right.left = new TreeNode(10);
		tree.root.left.right.left.left = new TreeNode(1);
		tree.root.left.right.right = new TreeNode(-4);
		tree.root.left.right.right.right = new TreeNode(7);
		tree.root.left.left = new TreeNode(2);
		tree.root.right = new TreeNode(-7);
		tree.root.right.right = new TreeNode(12);
		tree.root.right.right.left = new TreeNode(5);
		tree.root.right.right.right = new TreeNode(9);
		tree.root.right.right.right.right = new TreeNode(8);
		tree.middleLevelNode();
	}
}

input

 -6
 4 -7
 3
 -4 5
 7
// Include header file
#include <iostream>
#include <vector>
using namespace std;

// C++ program for
// Print the middle nodes of each level of a binary tree

// Binary Tree node
class TreeNode
{
	public: 
    int data;
	TreeNode *left;
	TreeNode *right;
	TreeNode(int data)
	{
		// Set node value
		this->data = data;
		this->left = NULL;
		this->right = NULL;
	}
};
// Queue Node
class QNode
{
	public: 
    TreeNode *n;
	QNode *next;
	QNode(TreeNode *n)
	{
		this->n = n;
		this->next = NULL;
	}
};
//Define custom queue class
class MyQueue
{
	public: 
    QNode *front;
	QNode *rear;
	int size;
	MyQueue()
	{
		this->front = NULL;
		this->rear = NULL;
		this->size = 0;
	}
	// Add a new node at last of queue
	void enqueue(TreeNode *n)
	{
		QNode *node = new QNode(n);
		if (this->front == NULL)
		{
			// When first node of queue
			this->front = node;
		}
		else
		{
			// Add node at last level
			this->rear->next = node;
		}
		this->size++;
		this->rear = node;
	}
	// Delete front node of queue
	void dequeue()
	{
      
		if (this->front != NULL)
		{
          	QNode *temp = this->front;
			if (this->rear == this->front)
			{
				this->rear = NULL;
				this->front = NULL;
			}
			else
			{
				this->front = this->front->next;
			}
			this->size--;
          	// Free memory
          	delete temp;
		}
	}
	int isSize()
	{
		return this->size;
	}
	bool isEmpty()
	{
		if (this->isSize() == 0)
		{
			return true;
		}
		return false;
	}
	TreeNode *peek()
	{
		if (this->isSize() == 0)
		{
			return NULL;
		}
		else
		{
			return this->front->n;
		}
	}
};
// Define Binary Tree
class BinaryTree
{
	public: TreeNode *root;
	BinaryTree()
	{
		this->root = NULL;
	}
	// Print the middle element of given level
	void printMiddleNode(vector < int > level)
	{
		if (level.size() > 0)
		{
			int middle = level.size() / 2;
			if ((level.size() % 2) == 0)
			{
				// When two middle element possible
				cout << "\n " << level.at(middle - 1);
				cout << " " << level.at(middle);
			}
			else
			{
				cout << "\n " << level.at(middle);
			}
		}
	}
	// This is display middle node of each level in binary tree
	void middleLevelNode()
	{
		if (this->root == NULL)
		{
			// When tree is empty
			return;
		}
		// Auxiliary queue which is capable to contain a tree level nodes
		MyQueue *q1 = new MyQueue();
		MyQueue *q2 = new MyQueue();
		// Auxiliary temp variable
		TreeNode *temp = NULL;
		int level = 1;
		// It will be use assemble a level node.
		vector < int > record ;
		// Add first node in q1
		q1->enqueue(this->root);
		// This loop execute until auxiliary queue q1 and q2 are not empty
		while (!q1->isEmpty() || !q2->isEmpty())
		{
			// Execute loop until q1 queue are not empty
			// And store the next level node in q2 queue
			while (!q1->isEmpty())
			{
				// Get top node of q1 queue
				temp = q1->peek();
				// Add node value
				record.push_back(temp->data);
				if (temp->left != NULL)
				{
					q2->enqueue(temp->left);
				}
				if (temp->right != NULL)
				{
					q2->enqueue(temp->right);
				}
				// Remove top element of q1 queue
				q1->dequeue();
			}
			this->printMiddleNode(record);
			record.clear();
			level++;
			// Execute loop until q2 queue are not empty
			// And store the next level node in q1 queue
			while (!q2->isEmpty())
			{
				// Get top node of q2 queue
				temp = q2->peek();
				// Add node value
				record.push_back(temp->data);
				if (temp->left != NULL)
				{
					q1->enqueue(temp->left);
				}
				if (temp->right != NULL)
				{
					q1->enqueue(temp->right);
				}
				// Remove top element of q2 queue
				q2->dequeue();
			}
			this->printMiddleNode(record);
			record.clear();
			level++;
		}
	}
};
int main()
{
	BinaryTree *tree = new BinaryTree();
	/*
	    Create Binary Tree
	    -----------------
	         -6                            
	       /   \    
	      4    -7    
	     / \     \               
	    2   3     12
	       / \   /  \
	      10 -4 5    9
	     /     \      \
	    1      7      8
	*/
	tree->root = new TreeNode(-6);
	tree->root->left = new TreeNode(4);
	tree->root->left->right = new TreeNode(3);
	tree->root->left->right->left = new TreeNode(10);
	tree->root->left->right->left->left = new TreeNode(1);
	tree->root->left->right->right = new TreeNode(-4);
	tree->root->left->right->right->right = new TreeNode(7);
	tree->root->left->left = new TreeNode(2);
	tree->root->right = new TreeNode(-7);
	tree->root->right->right = new TreeNode(12);
	tree->root->right->right->left = new TreeNode(5);
	tree->root->right->right->right = new TreeNode(9);
	tree->root->right->right->right->right = new TreeNode(8);
	tree->middleLevelNode();
	return 0;
}

input

 -6
 4 -7
 3
 -4 5
 7
// Include namespace system
using System;
using System.Collections.Generic;
// Csharp program for
// Print the middle nodes of each level of a binary tree

// Binary Tree node
public class TreeNode
{
	public int data;
	public TreeNode left;
	public TreeNode right;
	public TreeNode(int data)
	{
		// Set node value
		this.data = data;
		this.left = null;
		this.right = null;
	}
}
// Queue Node
public class QNode
{
	public TreeNode n;
	public QNode next;
	public QNode(TreeNode n)
	{
		this.n = n;
		this.next = null;
	}
}
//Define custom queue class
public class MyQueue
{
	public QNode front;
	public QNode rear;
	public int size;
	public MyQueue()
	{
		this.front = null;
		this.rear = null;
		this.size = 0;
	}
	// Add a new node at last of queue
	public void enqueue(TreeNode n)
	{
		QNode node = new QNode(n);
		if (this.front == null)
		{
			// When first node of queue
			this.front = node;
		}
		else
		{
			// Add node at last level
			this.rear.next = node;
		}
		this.size++;
		this.rear = node;
	}
	// Delete front node of queue
	public void dequeue()
	{
		if (this.front != null)
		{
			if (this.rear == this.front)
			{
				this.rear = null;
				this.front = null;
			}
			else
			{
				this.front = this.front.next;
			}
			this.size--;
		}
	}
	public int isSize()
	{
		return this.size;
	}
	public Boolean isEmpty()
	{
		if (this.isSize() == 0)
		{
			return true;
		}
		return false;
	}
	public TreeNode peek()
	{
		if (this.isSize() == 0)
		{
			return null;
		}
		else
		{
			return this.front.n;
		}
	}
}
// Define Binary Tree
public class BinaryTree
{
	public TreeNode root;
	public BinaryTree()
	{
		this.root = null;
	}
	// Print the middle element of given level
	public void printMiddleNode(List<int> level)
	{
		if (level.Count > 0)
		{
			int middle = level.Count / 2;
			if ((level.Count % 2) == 0)
			{
				// When two middle element possible
				Console.Write("\n " + level[middle - 1]);
				Console.Write(" " + level[middle]);
			}
			else
			{
				Console.Write("\n " + level[middle]);
			}
		}
	}
	// This is display middle node of each level in binary tree
	public void middleLevelNode()
	{
		if (this.root == null)
		{
			// When tree is empty
			return;
		}
		// Auxiliary queue which is capable to contain a tree level nodes
		MyQueue q1 = new MyQueue();
		MyQueue q2 = new MyQueue();
		// Auxiliary temp variable
		TreeNode temp = null;
		int level = 1;
		// It will be use assemble a level node.
		List < int > record = new List < int > ();
		// Add first node in q1
		q1.enqueue(this.root);
		// This loop execute until auxiliary queue q1 and q2 are not empty
		while (!q1.isEmpty() || !q2.isEmpty())
		{
			// Execute loop until q1 queue are not empty
			// And store the next level node in q2 queue
			while (!q1.isEmpty())
			{
				// Get top node of q1 queue
				temp = q1.peek();
				// Add node value
				record.Add(temp.data);
				if (temp.left != null)
				{
					q2.enqueue(temp.left);
				}
				if (temp.right != null)
				{
					q2.enqueue(temp.right);
				}
				// Remove top element of q1 queue
				q1.dequeue();
			}
			this.printMiddleNode(record);
			record.Clear();
			level++;
			// Execute loop until q2 queue are not empty
			// And store the next level node in q1 queue
			while (!q2.isEmpty())
			{
				// Get top node of q2 queue
				temp = q2.peek();
				// Add node value
				record.Add(temp.data);
				if (temp.left != null)
				{
					q1.enqueue(temp.left);
				}
				if (temp.right != null)
				{
					q1.enqueue(temp.right);
				}
				// Remove top element of q2 queue
				q2.dequeue();
			}
			this.printMiddleNode(record);
			record.Clear();
			level++;
		}
	}
	public static void Main(String[] args)
	{
		BinaryTree tree = new BinaryTree();
		/*
		    Create Binary Tree
		    -----------------
		         -6                            
		       /   \    
		      4    -7    
		     / \     \               
		    2   3     12
		       / \   /  \
		      10 -4 5    9
		     /     \      \
		    1      7      8
		*/
		tree.root = new TreeNode(-6);
		tree.root.left = new TreeNode(4);
		tree.root.left.right = new TreeNode(3);
		tree.root.left.right.left = new TreeNode(10);
		tree.root.left.right.left.left = new TreeNode(1);
		tree.root.left.right.right = new TreeNode(-4);
		tree.root.left.right.right.right = new TreeNode(7);
		tree.root.left.left = new TreeNode(2);
		tree.root.right = new TreeNode(-7);
		tree.root.right.right = new TreeNode(12);
		tree.root.right.right.left = new TreeNode(5);
		tree.root.right.right.right = new TreeNode(9);
		tree.root.right.right.right.right = new TreeNode(8);
		tree.middleLevelNode();
	}
}

input

 -6
 4 -7
 3
 -4 5
 7
<?php
// Php program for
// Print the middle nodes of each level of a binary tree

// Binary Tree node
class TreeNode
{
	public $data;
	public $left;
	public $right;
	public	function __construct($data)
	{
		// Set node value
		$this->data = $data;
		$this->left = NULL;
		$this->right = NULL;
	}
}
// Queue Node
class QNode
{
	public $n;
	public $next;
	public	function __construct($n)
	{
		$this->n = $n;
		$this->next = NULL;
	}
}
//Define custom queue class
class MyQueue
{
	public $front;
	public $rear;
	public $size;
	public	function __construct()
	{
		$this->front = NULL;
		$this->rear = NULL;
		$this->size = 0;
	}
	// Add a new node at last of queue
	public	function enqueue($n)
	{
		$node = new QNode($n);
		if ($this->front == NULL)
		{
			// When first node of queue
			$this->front = $node;
		}
		else
		{
			// Add node at last level
			$this->rear->next = $node;
		}
		$this->size++;
		$this->rear = $node;
	}
	// Delete front node of queue
	public	function dequeue()
	{
		if ($this->front != NULL)
		{
			if ($this->rear == $this->front)
			{
				$this->rear = NULL;
				$this->front = NULL;
			}
			else
			{
				$this->front = $this->front->next;
			}
			$this->size--;
		}
	}
	public	function isSize()
	{
		return $this->size;
	}
	public	function isEmpty()
	{
		if ($this->isSize() == 0)
		{
			return true;
		}
		return false;
	}
	public	function peek()
	{
		if ($this->isSize() == 0)
		{
			return NULL;
		}
		else
		{
			return $this->front->n;
		}
	}
}
// Define Binary Tree
class BinaryTree
{
	public $root;
	public	function __construct()
	{
		$this->root = NULL;
	}
	// Print the middle element of given level
	public	function printMiddleNode($level)
	{
		if (count($level) > 0)
		{
			$middle = (int)(count($level) / 2);
			if ((count($level) % 2) == 0)
			{
				// When two middle element possible
				echo("\n ".$level[$middle - 1]);
				echo(" ".$level[$middle]);
			}
			else
			{
				echo("\n ".$level[$middle]);
			}
		}
	}
	// This is display middle node of each level in binary tree
	public	function middleLevelNode()
	{
		if ($this->root == NULL)
		{
			// When tree is empty
			return;
		}
		// Auxiliary queue which is capable to contain a tree level nodes
		$q1 = new MyQueue();
		$q2 = new MyQueue();
		// Auxiliary temp variable
		$temp = NULL;
		$level = 1;
		// It will be use assemble a level node.
		$record =  array();
		// Add first node in q1
		$q1->enqueue($this->root);
		// This loop execute until auxiliary queue q1 and q2 are not empty
		while (!$q1->isEmpty() || !$q2->isEmpty())
		{
			// Execute loop until q1 queue are not empty
			// And store the next level node in q2 queue
			while (!$q1->isEmpty())
			{
				// Get top node of q1 queue
				$temp = $q1->peek();
				// Add node value
				$record[] = $temp->data;
				if ($temp->left != NULL)
				{
					$q2->enqueue($temp->left);
				}
				if ($temp->right != NULL)
				{
					$q2->enqueue($temp->right);
				}
				// Remove top element of q1 queue
				$q1->dequeue();
			}
			$this->printMiddleNode($record);
			$record = array();
			$level++;
			// Execute loop until q2 queue are not empty
			// And store the next level node in q1 queue
			while (!$q2->isEmpty())
			{
				// Get top node of q2 queue
				$temp = $q2->peek();
				// Add node value
				$record[] = $temp->data;
				if ($temp->left != NULL)
				{
					$q1->enqueue($temp->left);
				}
				if ($temp->right != NULL)
				{
					$q1->enqueue($temp->right);
				}
				// Remove top element of q2 queue
				$q2->dequeue();
			}
			$this->printMiddleNode($record);
			$record = array();
			$level++;
		}
	}
}

function main()
{
	$tree = new BinaryTree();
	/*
	    Create Binary Tree
	    -----------------
	         -6                            
	       /   \    
	      4    -7    
	     / \     \               
	    2   3     12
	       / \   /  \
	      10 -4 5    9
	     /     \      \
	    1      7      8
	*/
	$tree->root = new TreeNode(-6);
	$tree->root->left = new TreeNode(4);
	$tree->root->left->right = new TreeNode(3);
	$tree->root->left->right->left = new TreeNode(10);
	$tree->root->left->right->left->left = new TreeNode(1);
	$tree->root->left->right->right = new TreeNode(-4);
	$tree->root->left->right->right->right = new TreeNode(7);
	$tree->root->left->left = new TreeNode(2);
	$tree->root->right = new TreeNode(-7);
	$tree->root->right->right = new TreeNode(12);
	$tree->root->right->right->left = new TreeNode(5);
	$tree->root->right->right->right = new TreeNode(9);
	$tree->root->right->right->right->right = new TreeNode(8);
	$tree->middleLevelNode();
}
main();

input

 -6
 4 -7
 3
 -4 5
 7
// Node JS program for
// Print the middle nodes of each level of a binary tree

// Binary Tree node
class TreeNode
{
	constructor(data)
	{
		// Set node value
		this.data = data;
		this.left = null;
		this.right = null;
	}
}
// Queue Node
class QNode
{
	constructor(n)
	{
		this.n = n;
		this.next = null;
	}
}
//Define custom queue class
class MyQueue
{
	constructor()
	{
		this.front = null;
		this.rear = null;
		this.size = 0;
	}
	// Add a new node at last of queue
	enqueue(n)
	{
		var node = new QNode(n);
		if (this.front == null)
		{
			// When first node of queue
			this.front = node;
		}
		else
		{
			// Add node at last level
			this.rear.next = node;
		}
		this.size++;
		this.rear = node;
	}
	// Delete front node of queue
	dequeue()
	{
		if (this.front != null)
		{
			if (this.rear == this.front)
			{
				this.rear = null;
				this.front = null;
			}
			else
			{
				this.front = this.front.next;
			}
			this.size--;
		}
	}
	isSize()
	{
		return this.size;
	}
	isEmpty()
	{
		if (this.isSize() == 0)
		{
			return true;
		}
		return false;
	}
	peek()
	{
		if (this.isSize() == 0)
		{
			return null;
		}
		else
		{
			return this.front.n;
		}
	}
}
// Define Binary Tree
class BinaryTree
{
	constructor()
	{
		this.root = null;
	}
	// Print the middle element of given level
	printMiddleNode(level)
	{
		if (level.length > 0)
		{
			var middle = parseInt(level.length / 2);
			if ((level.length % 2) == 0)
			{
				// When two middle element possible
				process.stdout.write("\n " + level[middle - 1]);
				process.stdout.write(" " + level[middle]);
			}
			else
			{
				process.stdout.write("\n " + level[middle]);
			}
		}
	}
	// This is display middle node of each level in binary tree
	middleLevelNode()
	{
		if (this.root == null)
		{
			// When tree is empty
			return;
		}
		// Auxiliary queue which is capable to contain a tree level nodes
		var q1 = new MyQueue();
		var q2 = new MyQueue();
		// Auxiliary temp variable
		var temp = null;
		var level = 1;
		// It will be use assemble a level node.
		var record = [];
		// Add first node in q1
		q1.enqueue(this.root);
		// This loop execute until auxiliary queue q1 and q2 are not empty
		while (!q1.isEmpty() || !q2.isEmpty())
		{
			// Execute loop until q1 queue are not empty
			// And store the next level node in q2 queue
			while (!q1.isEmpty())
			{
				// Get top node of q1 queue
				temp = q1.peek();
				// Add node value
				record.push(temp.data);
				if (temp.left != null)
				{
					q2.enqueue(temp.left);
				}
				if (temp.right != null)
				{
					q2.enqueue(temp.right);
				}
				// Remove top element of q1 queue
				q1.dequeue();
			}
			this.printMiddleNode(record);
			record = [];
			level++;
			// Execute loop until q2 queue are not empty
			// And store the next level node in q1 queue
			while (!q2.isEmpty())
			{
				// Get top node of q2 queue
				temp = q2.peek();
				// Add node value
				record.push(temp.data);
				if (temp.left != null)
				{
					q1.enqueue(temp.left);
				}
				if (temp.right != null)
				{
					q1.enqueue(temp.right);
				}
				// Remove top element of q2 queue
				q2.dequeue();
			}
			this.printMiddleNode(record);
			record = [];
			level++;
		}
	}
}

function main()
{
	var tree = new BinaryTree();
	/*
	    Create Binary Tree
	    -----------------
	         -6                            
	       /   \    
	      4    -7    
	     / \     \               
	    2   3     12
	       / \   /  \
	      10 -4 5    9
	     /     \      \
	    1      7      8
	*/
	tree.root = new TreeNode(-6);
	tree.root.left = new TreeNode(4);
	tree.root.left.right = new TreeNode(3);
	tree.root.left.right.left = new TreeNode(10);
	tree.root.left.right.left.left = new TreeNode(1);
	tree.root.left.right.right = new TreeNode(-4);
	tree.root.left.right.right.right = new TreeNode(7);
	tree.root.left.left = new TreeNode(2);
	tree.root.right = new TreeNode(-7);
	tree.root.right.right = new TreeNode(12);
	tree.root.right.right.left = new TreeNode(5);
	tree.root.right.right.right = new TreeNode(9);
	tree.root.right.right.right.right = new TreeNode(8);
	tree.middleLevelNode();
}
main();

input

 -6
 4 -7
 3
 -4 5
 7
#  Python 3 program for
#  Print the middle nodes of each level of a binary tree

#  Binary Tree node
class TreeNode :
	def __init__(self, data) :
		#  Set node value
		self.data = data
		self.left = None
		self.right = None
	

#  Queue Node
class QNode :
	def __init__(self, n) :
		self.n = n
		self.next = None
	

# Define custom queue class
class MyQueue :
	def __init__(self) :
		self.front = None
		self.rear = None
		self.size = 0
	
	#  Add a new node at last of queue
	def enqueue(self, n) :
		node = QNode(n)
		if (self.front == None) :
			#  When first node of queue
			self.front = node
		else :
			#  Add node at last level
			self.rear.next = node
		
		self.size += 1
		self.rear = node
	
	#  Delete front node of queue
	def dequeue(self) :
		if (self.front != None) :
			if (self.rear == self.front) :
				self.rear = None
				self.front = None
			else :
				self.front = self.front.next
			
			self.size -= 1
		
	
	def isSize(self) :
		return self.size
	
	def isEmpty(self) :
		if (self.isSize() == 0) :
			return True
		
		return False
	
	def peek(self) :
		if (self.isSize() == 0) :
			return None
		else :
			return self.front.n
		
	

#  Define Binary Tree
class BinaryTree :
	def __init__(self) :
		self.root = None
	
	#  Print the middle element of given level
	def printMiddleNode(self, level) :
		if (len(level) > 0) :
			middle = int(len(level) / 2)
			if ((len(level) % 2) == 0) :
				#  When two middle element possible
				print("\n ", level[middle - 1], end = "")
				print(" ", level[middle], end = "")
			else :
				print("\n ", level[middle], end = "")
			
		
	
	#  This is display middle node of each level in binary tree
	def middleLevelNode(self) :
		if (self.root == None) :
			#  When tree is empty
			return
		
		#  Auxiliary queue which is capable to contain a tree level nodes
		q1 = MyQueue()
		q2 = MyQueue()
		#  Auxiliary temp variable
		temp = None
		level = 1
		#  It will be use assemble a level node.
		record = []
		#  Add first node in q1
		q1.enqueue(self.root)
		#  This loop execute until auxiliary queue q1 and q2 are not empty
		while (not q1.isEmpty() or not q2.isEmpty()) :
			#  Execute loop until q1 queue are not empty
			#  And store the next level node in q2 queue
			while (not q1.isEmpty()) :
				#  Get top node of q1 queue
				temp = q1.peek()
				#  Add node value
				record.append(temp.data)
				if (temp.left != None) :
					q2.enqueue(temp.left)
				
				if (temp.right != None) :
					q2.enqueue(temp.right)
				
				#  Remove top element of q1 queue
				q1.dequeue()
			
			self.printMiddleNode(record)
			record.clear()
			level += 1
			#  Execute loop until q2 queue are not empty
			#  And store the next level node in q1 queue
			while (not q2.isEmpty()) :
				#  Get top node of q2 queue
				temp = q2.peek()
				#  Add node value
				record.append(temp.data)
				if (temp.left != None) :
					q1.enqueue(temp.left)
				
				if (temp.right != None) :
					q1.enqueue(temp.right)
				
				#  Remove top element of q2 queue
				q2.dequeue()
			
			self.printMiddleNode(record)
			record.clear()
			level += 1
		
	

def main() :
	tree = BinaryTree()
	#    Create Binary Tree
	#    -----------------
	#         -6                            
	#       /   \    
	#      4    -7    
	#     / \     \               
	#    2   3     12
	#       / \   /  \
	#      10 -4 5    9
	#     /     \      \
	#    1      7      8
	tree.root = TreeNode(-6)
	tree.root.left = TreeNode(4)
	tree.root.left.right = TreeNode(3)
	tree.root.left.right.left = TreeNode(10)
	tree.root.left.right.left.left = TreeNode(1)
	tree.root.left.right.right = TreeNode(-4)
	tree.root.left.right.right.right = TreeNode(7)
	tree.root.left.left = TreeNode(2)
	tree.root.right = TreeNode(-7)
	tree.root.right.right = TreeNode(12)
	tree.root.right.right.left = TreeNode(5)
	tree.root.right.right.right = TreeNode(9)
	tree.root.right.right.right.right = TreeNode(8)
	tree.middleLevelNode()

if __name__ == "__main__": main()

input

  -6
  4  -7
  3
  -4  5
  7
#  Ruby program for
#  Print the middle nodes of each level of a binary tree

#  Binary Tree node
class TreeNode 
	# Define the accessor and reader of class TreeNode
	attr_reader :data, :left, :right
	attr_accessor :data, :left, :right
	def initialize(data) 
		#  Set node value
		self.data = data
		self.left = nil
		self.right = nil
	end

end

#  Queue Node
class QNode 
	# Define the accessor and reader of class QNode
	attr_reader :n, :next
	attr_accessor :n, :next
	def initialize(n) 
		self.n = n
		self.next = nil
	end

end

# Define custom queue class
class MyQueue 
	# Define the accessor and reader of class MyQueue
	attr_reader :front, :rear, :size
	attr_accessor :front, :rear, :size
	def initialize() 
		self.front = nil
		self.rear = nil
		self.size = 0
	end

	#  Add a new node at last of queue
	def enqueue(n) 
		node = QNode.new(n)
		if (self.front == nil) 
			#  When first node of queue
			self.front = node
		else 
			#  Add node at last level
			self.rear.next = node
		end

		self.size += 1
		self.rear = node
	end

	#  Delete front node of queue
	def dequeue() 
		if (self.front != nil) 
			if (self.rear == self.front) 
				self.rear = nil
				self.front = nil
			else 
				self.front = self.front.next
			end

			self.size -= 1
		end

	end

	def isSize() 
		return self.size
	end

	def isEmpty() 
		if (self.isSize() == 0) 
			return true
		end

		return false
	end

	def peek() 
		if (self.isSize() == 0) 
			return nil
		else 
			return self.front.n
		end

	end

end

#  Define Binary Tree
class BinaryTree 
	# Define the accessor and reader of class BinaryTree
	attr_reader :root
	attr_accessor :root
	def initialize() 
		self.root = nil
	end

	#  Print the middle element of given level
	def printMiddleNode(level) 
		if (level.length > 0) 
			middle = level.length / 2
			if ((level.length % 2) == 0) 
				#  When two middle element possible
				print("\n ", level[middle - 1])
				print(" ", level[middle])
			else 
				print("\n ", level[middle])
			end

		end

	end

	#  This is display middle node of each level in binary tree
	def middleLevelNode() 
		if (self.root == nil) 
			#  When tree is empty
			return
		end

		#  Auxiliary queue which is capable to contain a tree level nodes
		q1 = MyQueue.new()
		q2 = MyQueue.new()
		#  Auxiliary temp variable
		temp = nil
		level = 1
		#  It will be use assemble a level node.
		record = []
		#  Add first node in q1
		q1.enqueue(self.root)
		#  This loop execute until auxiliary queue q1 and q2 are not empty
		while (!q1.isEmpty() || !q2.isEmpty()) 
			#  Execute loop until q1 queue are not empty
			#  And store the next level node in q2 queue
			while (!q1.isEmpty()) 
				#  Get top node of q1 queue
				temp = q1.peek()
				#  Add node value
				record.push(temp.data)
				if (temp.left != nil) 
					q2.enqueue(temp.left)
				end

				if (temp.right != nil) 
					q2.enqueue(temp.right)
				end

				#  Remove top element of q1 queue
				q1.dequeue()
			end

			self.printMiddleNode(record)
			record.clear()
			level += 1
			#  Execute loop until q2 queue are not empty
			#  And store the next level node in q1 queue
			while (!q2.isEmpty()) 
				#  Get top node of q2 queue
				temp = q2.peek()
				#  Add node value
				record.push(temp.data)
				if (temp.left != nil) 
					q1.enqueue(temp.left)
				end

				if (temp.right != nil) 
					q1.enqueue(temp.right)
				end

				#  Remove top element of q2 queue
				q2.dequeue()
			end

			self.printMiddleNode(record)
			record.clear()
			level += 1
		end

	end

end

def main() 
	tree = BinaryTree.new()
	#    Create Binary Tree
	#    -----------------
	#         -6                            
	#       /   \    
	#      4    -7    
	#     / \     \               
	#    2   3     12
	#       / \   /  \
	#      10 -4 5    9
	#     /     \      \
	#    1      7      8
	tree.root = TreeNode.new(-6)
	tree.root.left = TreeNode.new(4)
	tree.root.left.right = TreeNode.new(3)
	tree.root.left.right.left = TreeNode.new(10)
	tree.root.left.right.left.left = TreeNode.new(1)
	tree.root.left.right.right = TreeNode.new(-4)
	tree.root.left.right.right.right = TreeNode.new(7)
	tree.root.left.left = TreeNode.new(2)
	tree.root.right = TreeNode.new(-7)
	tree.root.right.right = TreeNode.new(12)
	tree.root.right.right.left = TreeNode.new(5)
	tree.root.right.right.right = TreeNode.new(9)
	tree.root.right.right.right.right = TreeNode.new(8)
	tree.middleLevelNode()
end

main()

input

 -6
 4 -7
 3
 -4 5
 7
import scala.collection.mutable._;
// Scala program for
// Print the middle nodes of each level of a binary tree

// Binary Tree node
class TreeNode(var data: Int , var left: TreeNode , var right: TreeNode)
{
	def this(data: Int)
	{
		// Set node value
		this(data,null,null);
	}
}
// Queue Node
class QNode(var n: TreeNode , var next: QNode)
{
	def this(n: TreeNode)
	{
		this(n,null);
	}
}
//Define custom queue class
class MyQueue(var front: QNode , var rear: QNode , var size: Int)
{
	def this()
	{
		this(null, null,0);
	}
	// Add a new node at last of queue
	def enqueue(n: TreeNode): Unit = {
		var node: QNode = new QNode(n);
		if (this.front == null)
		{
			// When first node of queue
			this.front = node;
		}
		else
		{
			// Add node at last level
			this.rear.next = node;
		}
		this.size += 1;
		this.rear = node;
	}
	// Delete front node of queue
	def dequeue(): Unit = {
		if (this.front != null)
		{
			if (this.rear == this.front)
			{
				this.rear = null;
				this.front = null;
			}
			else
			{
				this.front = this.front.next;
			}
			this.size -= 1;
		}
	}
	def isSize(): Int = {
		return this.size;
	}
	def isEmpty(): Boolean = {
		if (this.isSize() == 0)
		{
			return true;
		}
		return false;
	}
	def peek(): TreeNode = {
		if (this.isSize() == 0)
		{
			return null;
		}
		else
		{
			return this.front.n;
		}
	}
}
// Define Binary Tree
class BinaryTree(var root: TreeNode)
{
	def this()
	{
		this(null);
	}
	// Print the middle element of given level
	def printMiddleNode(level: ArrayBuffer[Int]): Unit = {
		if (level.size > 0)
		{
			var middle: Int = level.size / 2;
			if ((level.size % 2) == 0)
			{
				// When two middle element possible
				print("\n " + level(middle - 1));
				print(" " + level(middle));
			}
			else
			{
				print("\n " + level(middle));
			}
		}
	}
	// This is display middle node of each level in binary tree
	def middleLevelNode(): Unit = {
		if (this.root == null)
		{
			// When tree is empty
			return;
		}
		// Auxiliary queue which is capable to contain a tree level nodes
		var q1: MyQueue = new MyQueue();
		var q2: MyQueue = new MyQueue();
		// Auxiliary temp variable
		var temp: TreeNode = null;
		var level: Int = 1;
		// It will be use assemble a level node.
		var record: ArrayBuffer[Int] = new ArrayBuffer[Int]();
		// Add first node in q1
		q1.enqueue(this.root);
		// This loop execute until auxiliary queue q1 and q2 are not empty
		while (!q1.isEmpty() || !q2.isEmpty())
		{
			// Execute loop until q1 queue are not empty
			// And store the next level node in q2 queue
			while (!q1.isEmpty())
			{
				// Get top node of q1 queue
				temp = q1.peek();
				// Add node value
				record += temp.data;
				if (temp.left != null)
				{
					q2.enqueue(temp.left);
				}
				if (temp.right != null)
				{
					q2.enqueue(temp.right);
				}
				// Remove top element of q1 queue
				q1.dequeue();
			}
			printMiddleNode(record);
			record.clear();
			level += 1;
			// Execute loop until q2 queue are not empty
			// And store the next level node in q1 queue
			while (!q2.isEmpty())
			{
				// Get top node of q2 queue
				temp = q2.peek();
				// Add node value
				record += temp.data;
				if (temp.left != null)
				{
					q1.enqueue(temp.left);
				}
				if (temp.right != null)
				{
					q1.enqueue(temp.right);
				}
				// Remove top element of q2 queue
				q2.dequeue();
			}
			printMiddleNode(record);
			record.clear();
			level += 1;
		}
	}
}
object Main
{
	def main(args: Array[String]): Unit = {
		var tree: BinaryTree = new BinaryTree();
		/*
		    Create Binary Tree
		    -----------------
		         -6                            
		       /   \    
		      4    -7    
		     / \     \               
		    2   3     12
		       / \   /  \
		      10 -4 5    9
		     /     \      \
		    1      7      8
		*/
		tree.root = new TreeNode(-6);
		tree.root.left = new TreeNode(4);
		tree.root.left.right = new TreeNode(3);
		tree.root.left.right.left = new TreeNode(10);
		tree.root.left.right.left.left = new TreeNode(1);
		tree.root.left.right.right = new TreeNode(-4);
		tree.root.left.right.right.right = new TreeNode(7);
		tree.root.left.left = new TreeNode(2);
		tree.root.right = new TreeNode(-7);
		tree.root.right.right = new TreeNode(12);
		tree.root.right.right.left = new TreeNode(5);
		tree.root.right.right.right = new TreeNode(9);
		tree.root.right.right.right.right = new TreeNode(8);
		tree.middleLevelNode();
	}
}

input

 -6
 4 -7
 3
 -4 5
 7
// Swift 4 program for
// Print the middle nodes of each level of a binary tree

// Binary Tree node
class TreeNode
{
	var data: Int;
	var left: TreeNode? ;
	var right: TreeNode? ;
	init(_ data: Int)
	{
		// Set node value
		self.data = data;
		self.left = nil;
		self.right = nil;
	}
}
// Queue Node
class QNode
{
	var n: TreeNode? ;
	var next: QNode? ;
	init(_ n: TreeNode? )
	{
		self.n = n;
		self.next = nil;
	}
}
//Define custom queue class
class MyQueue
{
	var front: QNode? ;
	var rear: QNode? ;
	var size: Int;
	init()
	{
		self.front = nil;
		self.rear = nil;
		self.size = 0;
	}
	// Add a new node at last of queue
	func enqueue(_ n: TreeNode? )
	{
		let node: QNode = QNode(n);
		if (self.front == nil)
		{
			// When first node of queue
			self.front = node;
		}
		else
		{
			// Add node at last level
			self.rear!.next = node;
		}
		self.size += 1;
		self.rear = node;
	}
	// Delete front node of queue
	func dequeue()
	{
		if (self.front  != nil)
		{
			if (self.rear === self.front)
			{
				self.rear = nil;
				self.front = nil;
			}
			else
			{
				self.front = self.front!.next;
			}
			self.size -= 1;
		}
	}
	func isSize()->Int
	{
		return self.size;
	}
	func isEmpty()->Bool
	{
		if (self.isSize() == 0)
		{
			return true;
		}
		return false;
	}
	func peek()->TreeNode?
	{
		if (self.isSize() == 0)
		{
			return nil;
		}
		else
		{
			return self.front!.n;
		}
	}
}
// Define Binary Tree
class BinaryTree
{
	var root: TreeNode? ;
	init()
	{
		self.root = nil;
	}
	// Print the middle element of given level
	func printMiddleNode(_ level: [Int] )
	{
		if (level.count > 0)
		{
			let middle: Int = level.count / 2;
			if ((level.count % 2) == 0)
			{
				// When two middle element possible
				print("\n ", level[middle - 1], terminator: "");
				print(" ", level[middle], terminator: "");
			}
			else
			{
				print("\n ", level[middle], terminator: "");
			}
		}
	}
	// This is display middle node of each level in binary tree
	func middleLevelNode()
	{
		if (self.root == nil)
		{
			// When tree is empty
			return;
		}
		// Auxiliary queue which is capable to contain a tree level nodes
		let q1: MyQueue = MyQueue();
		let q2: MyQueue = MyQueue();
		// Auxiliary temp variable
		var temp: TreeNode? = nil;
		var level: Int = 1;
		// It will be use assemble a level node.
		var record: [Int] = [Int]();
		// Add first node in q1
		q1.enqueue(self.root);
		// This loop execute until auxiliary queue q1 and q2 are not empty
		while (!q1.isEmpty() || !q2.isEmpty())
		{
			// Execute loop until q1 queue are not empty
			// And store the next level node in q2 queue
			while (!q1.isEmpty())
			{
				// Get top node of q1 queue
				temp = q1.peek();
				// Add node value
				record.append(temp!.data);
				if (temp!.left  != nil)
				{
					q2.enqueue(temp!.left);
				}
				if (temp!.right  != nil)
				{
					q2.enqueue(temp!.right);
				}
				// Remove top element of q1 queue
				q1.dequeue();
			}
			self.printMiddleNode(record);
			record.removeAll();
			level += 1;
			// Execute loop until q2 queue are not empty
			// And store the next level node in q1 queue
			while (!q2.isEmpty())
			{
				// Get top node of q2 queue
				temp = q2.peek();
				// Add node value
				record.append(temp!.data);
				if (temp!.left  != nil)
				{
					q1.enqueue(temp!.left);
				}
				if (temp!.right  != nil)
				{
					q1.enqueue(temp!.right);
				}
				// Remove top element of q2 queue
				q2.dequeue();
			}
			self.printMiddleNode(record);
			record.removeAll();
			level += 1;
		}
	}
}
func main()
{
	let tree: BinaryTree = BinaryTree();
	/*
	    Create Binary Tree
	    -----------------
	         -6                            
	       /   \    
	      4    -7    
	     / \     \               
	    2   3     12
	       / \   /  \
	      10 -4 5    9
	     /     \      \
	    1      7      8
	*/
	tree.root = TreeNode(-6);
	tree.root!.left = TreeNode(4);
	tree.root!.left!.right = TreeNode(3);
	tree.root!.left!.right!.left = TreeNode(10);
	tree.root!.left!.right!.left!.left = TreeNode(1);
	tree.root!.left!.right!.right = TreeNode(-4);
	tree.root!.left!.right!.right!.right = TreeNode(7);
	tree.root!.left!.left = TreeNode(2);
	tree.root!.right = TreeNode(-7);
	tree.root!.right!.right = TreeNode(12);
	tree.root!.right!.right!.left = TreeNode(5);
	tree.root!.right!.right!.right = TreeNode(9);
	tree.root!.right!.right!.right!.right = TreeNode(8);
	tree.middleLevelNode();
}
main();

input

  -6
  4  -7
  3
  -4  5
  7
// Kotlin program for
// Print the middle nodes of each level of a binary tree

// Binary Tree node
class TreeNode
{
	var data: Int;
	var left: TreeNode ? ;
	var right: TreeNode ? ;
	constructor(data: Int)
	{
		// Set node value
		this.data = data;
		this.left = null;
		this.right = null;
	}
}
// Queue Node
class QNode
{
	var n: TreeNode ? ;
	var next: QNode ? ;
	constructor(n: TreeNode ? )
	{
		this.n = n;
		this.next = null;
	}
}
//Define custom queue class
class MyQueue
{
	var front: QNode ? ;
	var rear: QNode ? ;
	var size: Int;
	constructor()
	{
		this.front = null;
		this.rear = null;
		this.size = 0;
	}
	// Add a new node at last of queue
	fun enqueue(n: TreeNode ? ): Unit
	{
		val node: QNode = QNode(n);
		if (this.front == null)
		{
			// When first node of queue
			this.front = node;
		}
		else
		{
			// Add node at last level
			this.rear?.next = node;
		}
		this.size += 1;
		this.rear = node;
	}
	// Delete front node of queue
	fun dequeue(): Unit
	{
		if (this.front != null)
		{
			if (this.rear == this.front)
			{
				this.rear = null;
				this.front = null;
			}
			else
			{
				this.front = this.front?.next;
			}
			this.size -= 1;
		}
	}
	fun isSize(): Int
	{
		return this.size;
	}
	fun isEmpty(): Boolean
	{
		if (this.isSize() == 0)
		{
			return true;
		}
		return false;
	}
	fun peek(): TreeNode ?
	{
		if (this.isSize() == 0)
		{
			return null;
		}
		else
		{
			return this.front?.n;
		}
	}
}
// Define Binary Tree
class BinaryTree
{
	var root: TreeNode ? ;
	constructor()
	{
		this.root = null;
	}
	// Print the middle element of given level
	fun printMiddleNode(level: MutableList<Int> ): Unit
	{
		if (level.size > 0)
		{
			val middle: Int = level.size / 2;
			if ((level.size % 2) == 0)
			{
				// When two middle element possible
				print("\n " + level[middle - 1]);
				print(" " + level[middle]);
			}
			else
			{
				print("\n " + level[middle]);
			}
		}
	}
	// This is display middle node of each level in binary tree
	fun middleLevelNode(): Unit
	{
		if (this.root == null)
		{
			// When tree is empty
			return;
		}
		// Auxiliary queue which is capable to contain a tree level nodes
		val q1: MyQueue = MyQueue();
		val q2: MyQueue = MyQueue();
		// Auxiliary temp variable
		var temp: TreeNode ? ;
		var level: Int = 1;
		// It will be use assemble a level node.
		var record = mutableListOf<Int>();
		// Add first node in q1
		q1.enqueue(this.root);
		// This loop execute until auxiliary queue q1 and q2 are not empty
		while (!q1.isEmpty() || !q2.isEmpty())
		{
			// Execute loop until q1 queue are not empty
			// And store the next level node in q2 queue
			while (!q1.isEmpty())
			{
				// Get top node of q1 queue
				temp = q1.peek();
				// Add node value
				record.add(temp!!.data);
				if (temp.left != null)
				{
					q2.enqueue(temp.left);
				}
				if (temp.right != null)
				{
					q2.enqueue(temp.right);
				}
				// Remove top element of q1 queue
				q1.dequeue();
			}
			this.printMiddleNode(record);
			record.clear();
			level += 1;
			// Execute loop until q2 queue are not empty
			// And store the next level node in q1 queue
			while (!q2.isEmpty())
			{
				// Get top node of q2 queue
				temp = q2.peek();
				// Add node value
				record.add(temp!!.data);
				if (temp.left != null)
				{
					q1.enqueue(temp.left);
				}
				if (temp.right != null)
				{
					q1.enqueue(temp.right);
				}
				// Remove top element of q2 queue
				q2.dequeue();
			}
			this.printMiddleNode(record);
			record.clear();
			level += 1;
		}
	}
}
fun main(args: Array < String > ): Unit
{
	val tree: BinaryTree = BinaryTree();
	/*
	    Create Binary Tree
	    -----------------
	         -6                            
	       /   \    
	      4    -7    
	     / \     \               
	    2   3     12
	       / \   /  \
	      10 -4 5    9
	     /     \      \
	    1      7      8
	*/
	tree.root = TreeNode(-6);
	tree.root?.left = TreeNode(4);
	tree.root?.left?.right = TreeNode(3);
	tree.root?.left?.right?.left = TreeNode(10);
	tree.root?.left?.right?.left?.left = TreeNode(1);
	tree.root?.left?.right?.right = TreeNode(-4);
	tree.root?.left?.right?.right?.right = TreeNode(7);
	tree.root?.left?.left = TreeNode(2);
	tree.root?.right = TreeNode(-7);
	tree.root?.right?.right = TreeNode(12);
	tree.root?.right?.right?.left = TreeNode(5);
	tree.root?.right?.right?.right = TreeNode(9);
	tree.root?.right?.right?.right?.right = TreeNode(8);
	tree.middleLevelNode();
}

input

 -6
 4 -7
 3
 -4 5
 7

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