PrintLeftViewIterative1

							//using in-order traversal
import java.util.Stack;					//Time Complexity: O(n)
/* 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
{
     static Node root;
	// recursive function to print left view
	void leftViewUtil(Node node)
	{
		// Base Case
		if (node==null) return;
	//keep the nodes in the path that are waiting to be visited
		Stack<Node> stack = new Stack<Node>();
		
		//first node to be visited will be the left one
		while (node != null) {
		    System.out.print(node.data + " ");
			stack.push(node);
			node = node.left;
		}
		
		// traverse the tree
		while (stack.size() > 0) {
		    	
			// visit the top node
			node = stack.pop();
			if (node.right != null) {
				node = node.right;
				
				// the next node to be visited is the leftmost
				while (node != null) {
					stack.push(node);
					node = node.left;
					if(node!=null){
					    System.out.print(node.data + " ");
					}
				}
			}
		}

	}

	/* 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.leftViewUtil(root);
	}
}