Non recursive preorder traversal of binary tree

Question

hi,
I am trying to implement a non-recursive traversal of binary tree. I already know the recursive one.
I am trying to do it by using a Stack.
I begin by Pushing the root of an element on to a stack, and then run a while loop in which i pop an element of the stack and get its children from right to left. and push it in the same order on to the stack. So during the next iteration of my while loop the top most element gets popped and its children and pushed on to the stack in the above manner.
but when i pop an element from a stack its popped as an object so i dont know how to access its children.
help me i am really stuck.

Answer 1

Hi, I suppose you have something like this :
class Stack {
  public void push( Object object ) throws ... { ... }
  public Object pop() throws ... { ... }
class Element {
  Element elem;
  stack.push(elem);
  /* because pop() method return an object of type Object
  ** if you are sure that your stack only contains Element object
  ** then you need to cast (change the type of) what the pop() method
  ** returns in this way :
  elem = (Element)stack.pop();
  ...further reading on casting will be a good idea anyway.