Which of the following is NOT a valid binary tree traversal method?

Which of the following is NOT a valid binary tree traversal method?

Step 1: Understand what a binary tree is. A binary tree is a data structure where each node has at most two children.
Step 2: Learn about binary tree traversal methods. These are ways to visit all the nodes in a binary tree.
Step 3: Identify the common traversal methods: in-order (left, root, right), pre-order (root, left, right), and post-order (left, right, root).
Step 4: Look at the options given in the question. One of the options is 'Side-order'.
Step 5: Check if 'Side-order' is a recognized method. It is not listed among the common traversal methods.
Step 6: Conclude that 'Side-order' is NOT a valid binary tree traversal method.

No concepts available.