Non recursive algorithm for Post Order Traversal

For Pre,Post and In order traversals of a Binary tree,

it is very easy to write recursive programs/algorithms.

But when it comes to a non-recursive solution, it becomes

rather difficult. Though pre-order and in-order traversals

have non-recursive algorithms, which are slightly easier

to implement/understand, post-order is a tough nut to

crack.

Not any more.
Here is an easy to understand non-recursive algorithm

for post-order traversal :

Fact I : Post order traversal(Left-Right-Root) is the exact opposite

of Root-Right-Left traversal(RoRiL)(Prove it!).

Fact II : And a non-recursive algo for Pre-order(RoLRi) is equally good

for RoRiL.

So, just use the non-recursive algo for RoRiL(which is similar to Pre-order)

and traverse it backwards.(that's the post order traversal)

(Pre-order Non Recursive Algorithm)