Given a binary tree, print out the elements in order. Without recursion.

L = [node]
do{
        nextLevel=[]
        while L is not empty:
                n = pop(L)
                print n.val
                if n.left 
                        nextLevel.add(n.left)
                if n.right
                        nextLevel.add(n.right)
        L=nextLevel 
} while (nextLevel is not empty)