二叉树前、中、后序遍历

原创转载请注明出处：https://www.cnblogs.com/agilestyle/p/14950846.html

class TreeNode:
    def __init__(self, data):
        self.data = data
        self.left = None
        self.right = None


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

    def pre_order_traversal(self, root):
        """root -> left -> right"""
        if root is None:
            return
        print(root.data)
        self.pre_order_traversal(root.left)
        self.pre_order_traversal(root.right)
        return root

    def in_order_traversal(self, root):
        """left -> root -> right"""
        if root is None:
            return
        self.in_order_traversal(root.left)
        print(root.data)
        self.in_order_traversal(root.right)
        return root

    def post_order_traversal(self, root):
        """left -> right -> root"""
        if root is None:
            return
        self.post_order_traversal(root.left)
        self.post_order_traversal(root.right)
        print(root.data)
        return root


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

print("pre_order_traversal: ")
tree.pre_order_traversal(tree.root)
print("in_order_traversal: ")
tree.in_order_traversal(tree.root)
print("post_order_traversal: ")
tree.post_order_traversal(tree.root)