PrintLeftViewIterative2

// Java program to print left view of binary tree             //Using level order traversal
import java.util.Queue;						//Time Complexity: O(n)
import java.util.LinkedList;
/* Class containing left and right child of current
node and key value*/
class Node
{
	int data;
	Node left, right;

	public Node(int item)
	{
		data = item;
		left = right = null;
	}
}

/* Class to print the left view */
class BinaryTree
{
	Node root;
	static int max_level = 0;

	// recursive function to print left view
	void leftViewUtil(Node node)
	{
		// Base Case
		if (node==null) return;
		// Create an empty queue for level order tarversal
		Queue<Node> q =new LinkedList<Node>();
		
		// Enqueue Root and initialize height
		q.add(root);
		System.out.print(root.data + " ");
		
		
		while(true)
		{
			
			// nodeCount (queue size) indicates number of nodes
			// at current level.
			int nodeCount = q.size();
			if(nodeCount == 0)
				break;
			
			// Dequeue all nodes of current level and Enqueue all
			// nodes of next level
			while(nodeCount > 0)
			{
			    node = q.peek();
				q.remove();
				if(node.left != null)
					{
					q.add(node.left);
					System.out.print(node.left.data + " ");
					}
				if(node.right != null)
					q.add(node.right);
				nodeCount--;
			}
		}

	}

	// A wrapper over leftViewUtil()
	void leftView()
	{
		leftViewUtil(root);
	}

	/* testing for example nodes */
	public static void main(String args[])
	{
		/* creating a binary tree and entering the nodes */
		BinaryTree tree = new BinaryTree();
		tree.root = new Node(12);
		tree.root.left = new Node(10);
		tree.root.right = new Node(30);
		tree.root.right.left = new Node(25);
		tree.root.right.right = new Node(40);

		tree.leftView();
	}
}