Reconstructing Binary Tree by traversals arrays

Pre -> Root → Left → Right
IN -> Left → Root → Right
Post -> Left → Right → Root

Pre-Order: First node of pre-order traversal output is always the root.
Post-Order: Last node of post-order traversal output is always the root.

• In-order traversal gives us the relative ordering of nodes (left, root, right).
• Pre-order or Post-order tells us which node appears first or last, helping us determine the root and recursive subtrees.

Why Can't "Pre-order + Post-order" Reconstruct a Tree?

With Pre-order and Post-order, we know:

• Pre-order tells us the root first.
• Post-order tells us the root last.

However, we don’t know where to split the tree into left and right subtrees without in-order information.

Problems:

• https://neetcode.io/problems/binary-tree-from-preorder-and-inorder-traversal