Algorithms For Dummies

  Structuring Data 

     127

isn’t any error trapping. The 

nodeData

 entry can contain any value. The following 

code shows how to use the 

binaryTree

  class  to  build  the  tree  shown  in 

Figure 6-1:

tree = binaryTree("Root")

BranchA = binaryTree("Branch A")

BranchB = binaryTree("Branch B")

tree.left = BranchA

tree.right = BranchB

  

LeafC = binaryTree("Leaf C")

LeafD = binaryTree("Leaf D")

LeafE = binaryTree("Leaf E")

LeafF = binaryTree("Leaf F")

BranchA.left = LeafC

BranchA.right = LeafD

BranchB.left = LeafE

BranchB.right = LeafF

You have many options when building a tree, but building it from the top down (as 

shown in this code) or the bottom up (in which you build the leaves first) are two 

common  methods.  Of  course,  you  don’t  really  know  whether  the  tree  actually 

works at this point. Traversing the tree means checking the links and verifying that 

they actually do connect as you think they should. The following code shows how 

to use recursion (as described in Chapter 5) to traverse the tree you just built.

def traverse(tree):

    if tree.left != None:

        traverse(tree.left)

    if tree.right != None:

        traverse(tree.right)

    print(tree.nodeData)

  

traverse(tree)

  

Leaf C

Leaf D

Branch A

Leaf E

Leaf F

Branch B

Root

---

128

 

   

  PART 2