GATE DA 2026 Q25: Binary tree from preorder and inorder traversals

You are given the following Pre-order and In-order traversals of a Binary Tree T with nodes E, F, G, P, Q, R, S.

Pre-order: P Q S E R F G

In-order: S Q E P F R G

Which of the following statements is/are true about the Binary Tree T?

Try it: multiple select: one or more correct options

Select all correct options. No negative marking, no partial marks.

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Answer: A, B (official GATE 2026 final answer key)

Concept used: Preorder gives the root first; its position in inorder splits the left and right subtrees.

First step: Root P; inorder gives left {S, Q, E} with root Q (children S, E) and right {F, R, G} with root R (children F, G).

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