worksheet 30: Binary Search Tree Iterator Name:
An Active Learning Approach to Data Structures using C
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Worksheet 30: Binary Search Tree Iterator
In preparation: If you have not done so already, complete worksheet 29 to learn the
basic features of the binary search tree.
To make the BST a useful container we need an iterator. This iterator must produce the
elements in sequence. As we noted previously, this means making an in-order traversal of
the tree. Examine the following tree and see if you can guess an algorithm that will do
this. Remember that, in our implementation, nodes do not point back up to their parent
nodes. How will you remember the path you have followed down the tree?
As you might have guessed, one way to do this is to have the iterator maintain an internal
stack. This stack will represent the current path that has been traversed from root to leaf.
Notice that the first element that our iterator should produce is the leftmost child of the
root, and that furthermore all the nodes between the root and this point should be added
to the stack. A useful routine for this purpose is slideLeft:
Using the slideLeft routine, verify that the following
algorithm will produce the desired iterator traversal of
the binary search tree. The remove portion of the
iterator interface is more complex, and we will not
consider it here.
BSTIteratorInit
to initialize, create an empty stack
void slideLeft (Node n)
while n is not null
stack n
n = left child of n
