binary_tree_traversal.py

class Node:
    def __init__(self, data, left_node, right_node):
        self.data = data
        self.left_node = left_node
        self.right_node = right_node 
        
def pre_order(node):
    print(node.data, end=' ')
    if node.left_node != None:
        pre_order(tree[node.left_node])
    if node.right_node != None:
        pre_order(tree[node.right_node])
        
def in_order(node):
    if node.left_node != None:
        in_order(tree[node.left_node])
    print(node.data, end=' ')
    if node.right_node != None:
        in_order(tree[node.right_node])
        
def post_order(node):
    if node.left_node != None:
        post_order(tree[node.left_node])
    if node.right_node != None:
        post_order(tree[node.right_node])
    print(node.data, end=' ')
    

tree = {
    'A' : Node('A', 'B', 'C'),
    'B' : Node('B', 'D', 'E'),
    'C' : Node('C', 'F', None),
    'D' : Node('D', None, None),
    'E' : Node('E', None, None),
    'F' : Node('F', None, None)
}

# n = int(input())
# for i in range(n):
#     data, left_node, right_node = input().split()
#     if left_node == "None":
#         left_node = None
#     if right_node == "None":
#         right_node = None
#     tree[data] = Node(data, left_node, right_node)

pre_order(tree['A'])
print()
in_order(tree['A'])
print()
post_order(tree['A'])