binaryTreeClass.py

# https://www.youtube.com/watch?v=6oL-0TdVy28
# Common depth first search order: inorder, preorder, postorder

class Node():
    def __init__(self, value):
        self.value = value
        self.left = None
        self.right = None

class BinaryTree():
    def __init__(self, root):
        self.root = Node(root)


    def preorder_print(self, start, traversal):
        """Root->Left->Right"""
        
        if start:
            traversal += str(start.value) + "-"
            traversal = self.preorder_print(start.left, traversal)
            traversal = self.preorder_print(start.right, traversal)

        return traversal


    def inorder_print(self, start, traversal):
        """Left->Root->Right"""

        if start:
            traversal = self.inorder_print(start.left, traversal)
            traversal += str(start.value) + "-"
            traversal = self.inorder_print(start.right, traversal)
        
        return traversal


    def postorder_print(self, start, traversal):

        if start:
            traversal = self.postorder_print(start.left, traversal)
            traversal = self.postorder_print(start.right, traversal)
            traversal += str(start.value) + "-"
        
        return traversal

'''
            1
      2             3
4         5    6          7 

'''

tree = BinaryTree(1)
tree.root.left = Node(2)
tree.root.right = Node(3)
tree.root.left.left = Node(4)
tree.root.left.right = Node(5)
tree.root.right.left = Node(6)
tree.root.right.right = Node(7)

print(tree.preorder_print(tree.root,"")) # 1, 2, 4, 5, 3, 6, 7
print(tree.inorder_print(tree.root,"")) # 4 2 5 1 6 3 7
print(tree.postorder_print(tree.root,"")) # 4 5 2 6 7 3 1