Depth-first Search – (Preorder, Inorder, and Postorder)

This lecture provides a theoretical overview of tree traversal methods: preorder, inorder, and postorder. It explains a trick to derive these traversals, emphasizing that this method is not suitable for coding or interviews but useful for theoretical understanding. The lecture details how to perform each traversal and concludes with a generalization of the methods.

What is the primary focus of this lecture on tree traversals?

• Algorithm optimization

• Theoretical understanding

• Interview preparation

• Practical coding techniques

In the trick for preorder traversal, when is a node added to the result?

• When it has no children

• When visited for the last time

• When visited for the second time

• When visited for the first time

During inorder traversal using the trick, when is a node added to the result?

• When it has no children

• When visited for the second time

• When visited for the first time

• When visited for the last time

In postorder traversal, when is a node added to the result according to the trick?

• When visited for the second time

• When visited for the first time

• When visited for the last time

• When it has no children

What is the sequence of node visits in a preorder traversal?

• Left, Root, Right

• Right, Left, Root

• Root, Left, Right

• Left, Right, Root

In an inorder traversal, where is the root node placed in the sequence?

• After left and right

• Before left and right

• Between left and right

• Only if it has children

What is the order of node visits in a postorder traversal?

• Left, Right, Root

• Right, Left, Root

• Left, Root, Right

• Root, Left, Right