A short note on different BST traversals and if they can be reversed.
| Traversal | Order | Uniquely determines the BST? | Why |
|---|---|---|---|
| Inorder | Left → Root → Right | No | Inorder of any BST is just the keys in sorted order, so different BST shapes can have the same inorder traversal. |
| Preorder | Root → Left → Right | Yes | The first value is the root. Smaller values belong to the left subtree and larger values to the right, so the tree can be reconstructed recursively. |
| Postorder | Left → Right → Root | Yes | The last value is the root. Smaller values form the left subtree and larger values form the right subtree, so reconstruction is possible. |
| Level Order / BFS | Level by level | Yes | The root appears first, and BST value ranges (hi, lo) determine where each later node must be placed. |