Binary Tree Traversal-Modified

WAP to print the node values of a binary tree
- Even level starting from right to left
- Odd level starting from left to right
Assume that level of root is 1.
a
b c
d e f g
Output: a c b d e f g

Strategy:

Method 1:Two Stacks

static void print(Node root)
{
Stack<Node> odd = new Stack<Node>();
Stack<Node> even = new Stack<Node>();
odd.Push(root);
while (odd.Count != 0 || even.Count != 0)
{
while (odd.Count != 0)
{
Node node = odd.Pop();
if(node.left!=null)
even.Push(node.left);
if(node.right!=null)
even.Push(node.right);
Console.Write(node.data+" ");
}
Console.WriteLine();
while (even.Count != 0)
{
Node node = even.Pop();
if (node.right != null)
odd.Push(node.right);
if (node.left != null)
odd.Push(node.left);
Console.Write(node.data + " ");
}
Console.WriteLine();
}
}

Method 2:

 Breadth First Search with a stack can solve this problem.
1. Add the root node to the queue.
2. Get the head node of the queue and add its children to the queue.
3. If the node is in even level, print it. Otherwise, push it into the stack
4. When level of the head node has changed from odd to even,pop the stack and print the node
5. Repeat from 2 until all the node have been scaned