Binary Tree Basics in Python

Concepts: pyTreeNode, pyPreorder, pyInorder, pyPostorder

Every tree problem starts with the same class. LeetCode defines it. Every interviewer expects you to know it. Write it without hesitation the moment the problem is presented — it signals that you have done this before and you are comfortable with the domain. The TreeNode Class You can also use a dataclass, which is cleaner in Python 3.7+ and shows modern Python awareness. Either is acceptable in interviews; the dataclass version is a slight signal of production Python experience. The Three Traversal Orders Pre-order, in-order, and post-order differ only in when you process the current node relative to its children. Pre: node first, then children. In: left child, node, right child. Post: children first, node last. The recursive structure is identical — the only thing that changes is where y