Binary Tree Traversal

There are two main categories of Tree traversal
methods:

• Breadth First Search (BFS) is when the nodes on
  the same level are visited before going to the
  next level in the tree. This means that the tree
  is explored in a more sideways direction.
• Depth First Search (DFS) is when the traversal
  moves down the tree all the way to the leaf
  nodes, exploring the tree branch by branch in a
  downwards direction.

There are three different types of DFS traversals:

• pre-order
• in-order
• post-order

Pre-order Traversal of Binary Trees

def preOrderTraversal(node):
    if node is None:
        return
    print(node.data, end=", ")
    preOrderTraversal(node.left)
    preOrderTraversal(node.right)

In-order Traversal of Binary Trees

def inOrderTraversal(node):
    if node is None:
        return
    inOrderTraversal(node.left)
    print(node.data, end=", ")
    inOrderTraversal(node.right)

Post-order Traversal of Binary Trees

def postOrderTraversal(node):
    if node is None:
        return
    postOrderTraversal(node.left)
    postOrderTraversal(node.right)
    print(node.data, end=", ")