GATE CSE 2026 | Set 2 | Question: 2

Question

The set $\mathbf{T}$ represents various traversals over binary tree. The set $\mathbf{S}$ represents the order of visiting nodes during a traversal.
\[
\renewcommand{\arraystretch}{1.3}
\begin{array}{|l|l|}
\hline
\quad\quad\textbf{T} & \quad\quad\quad\textbf{S} \\
\hline
\text{I: Inorder} & \text{L: left subtree, node, right subtree} \\
\text{II: Preorder} & \text{M: node, left subtree, right subtree} \\
\text{III: Postorder} & \text{N: left subtree, right subtree, node} \\
\hline
\end{array}
\]
Which one of the following is the correct match from $\mathbf{T}$ to $\mathbf{S}$ ?

• A. $\mathrm{I}-\mathrm{L}, \mathrm{II}-\mathrm{M}, \mathrm{III}-\mathrm{N}$
• B. $\mathrm{I}-\mathrm{M}, \mathrm{II}-\mathrm{L}, \mathrm{III}-\mathrm{N}$
• C. $\mathrm{I}-\mathrm{N}, \mathrm{II}-\mathrm{M}, \mathrm{III}-\mathrm{L}$
• D. $\mathrm{I}-\mathrm{L}, \mathrm{II}-\mathrm{N}, \mathrm{III}-\mathrm{M}$

Comments

Refer Page 4

https://web.engr.oregonstate.edu/~sinisa/courses/OSU/CS261/lectures/BST.pdf

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very simple and basic question

inorder - left root right

preorder -  root left right

postorder - left, right,root

Answer 1

Do this  question Just by Defniation  of each 

Inorder = Left Subtre, Root Node, Right subtree.

Preorder = Root Node, LeftSubtree, Right Subtree.

Postorder = Left Subtree, Right Subtre, Root Node.

One thing common in all traversal  is that Left Subtre is visted first before Right Subtre.

so option A is correct (direct Matching)

Answer 2

In the context of tree traversing or simply traversal is the process of visiting every node in the tree exactly once in a specific, systematic order. Unlike linear data structures (like arrays or linked lists), which are usually traversed in a single logical way, trees are hierarchical and can be traversed in several different sequences.

1. Inorder Traversal (L-N-R)

In this method, the left subtree is visited first, followed by the root node, and finally the right subtree.

• Definition: Left Subtree$\rightarrow$  Root  $\rightarrow$ Right subtree

2. Preorder Traversal (N-L-R)

In this method, the root node is visited first, followed by the left subtree and then the right subtree.

• Definition: Root $\rightarrow$ left Subtree $\Rightarrow$ right subtree

3. Postorder Traversal (L-R-N)

In this method, we visit the left subtree first, then the right subtree, and finally the root node.

• Definition: Left Subtree$\rightarrow$ Right Subtree $\rightarrow$ Root

 

$(I-L),(II-M),(III-N)$

Answer 3

Inorder:left < node< right 

preorder : node < left < right

postorder : left < right < node

correct option : A

 

Answer 4

pre order  : Root , left sub tree, Right sb tree

in order : : left sub tree , Root, Right sub tree

post order : Left sub tree, Right sub tree, Root

 

option  :A is correct   I−L,II−M,III−N