GATE CSE 2026 Session 2 Q12: Match binary tree traversals with visiting orders

The set T represents various traversals over binary tree. The set S represents the order of visiting nodes during a traversal.

T	S
I: Inorder	L: left subtree, node, right subtree
II: Preorder	M: node, left subtree, right subtree
III: Postorder	N: left subtree, right subtree, node

Which one of the following is the correct match from T to S?

Try it: multiple choice: exactly one correct option

Wrong answer costs 1/3 mark in GATE.

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Answer: A (official GATE 2026 final answer key)

Concept used: The prefix in/pre/post tells where the node is visited relative to its subtrees.

First step: Inorder visits the node between the subtrees, preorder before them, postorder after them.

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Source: official GATE 2026 Session 2 CS question paper and final answer key, organised by IIT Guwahati. Question paper · Answer key