Find if a binary tree is height balanced ?

A Height Balanced Tree is tree where for each node this condition is true.
- The difference between heights of left subtree and right subtree for any node is not more than 1.

So we can say that a tree T is Height Balanced when
- Left Sub Tree of T is height balanced
- Right Sub Tree of T is height balanced
and for each node this above condition is true :P

Level order traversal in spiral form

Write a function to print spiral order traversal of a tree.
For below tree, function should print 1, 2, 3, 7, 6, 5, 4.

           [1]
          /   \
       [2]     [3]
      /  \     /  \ 
    [4]  [5] [6]  [7]