# Tree traversal methods (in-order, pre-order, post-order) MCQs

**What is the main purpose of tree traversal?**

A) To organize the tree

B) To search for a specific value

C) To visit all nodes in a tree

D) To delete nodes

**Answer: C) To visit all nodes in a tree**

**Which traversal method visits the left subtree, the root, and then the right subtree?**

A) Pre-order

B) In-order

C) Post-order

D) Level-order

**Answer: B) In-order**

**In which traversal method is the root node visited first?**

A) In-order

B) Pre-order

C) Post-order

D) Level-order

**Answer: B) Pre-order**

**What is the order of nodes visited in post-order traversal?**

A) Left, Right, Root

B) Root, Left, Right

C) Left, Root, Right

D) Right, Left, Root

**Answer: A) Left, Right, Root**

**Which of the following is true about in-order traversal of a binary search tree?**

A) It visits nodes in reverse order

B) It produces a sorted sequence of keys

C) It visits the root before the left child

D) It cannot be performed on an unbalanced tree

**Answer: B) It produces a sorted sequence of keys**

**How does pre-order traversal help in creating a copy of a tree?**

A) It visits nodes in sorted order

B) It visits the root before its children

C) It captures the structure of the tree

D) It requires less memory

**Answer: C) It captures the structure of the tree**

**Which traversal method is typically used for evaluating expression trees?**

A) In-order

B) Pre-order

C) Post-order

D) Level-order

**Answer: C) Post-order**

**What is the result of in-order traversal on the tree with nodes 1, 2, 3, where 2 is the root?**

A) 1, 2, 3

B) 2, 1, 3

C) 1, 3, 2

D) 3, 2, 1

**Answer: A) 1, 2, 3**

**In a binary tree, which traversal method can be used to print the nodes in reverse?**

A) Pre-order

B) Post-order

C) In-order

D) None of the above

**Answer: B) Post-order**

**What does the term “depth-first traversal” refer to?**

A) Visiting all nodes at the current level

B) Visiting nodes from the top to the bottom

C) Visiting nodes as deep as possible before backtracking

D) Visiting nodes in a sorted manner

**Answer: C) Visiting nodes as deep as possible before backtracking**

**Which traversal method uses a stack implicitly due to recursion?**

A) Level-order

B) In-order

C) Pre-order

D) All of the above

**Answer: D) All of the above**

**What is the output of a pre-order traversal on a tree with root A, left child B, and right child C?**

A) B, A, C

B) A, B, C

C) B, C, A

D) C, B, A

**Answer: B) A, B, C**

**Which traversal method is best for printing a tree structure in a human-readable format?**

A) In-order

B) Pre-order

C) Post-order

D) Level-order

**Answer: B) Pre-order**

**How are in-order and post-order traversals different?**

A) They visit the root at different times

B) They only visit leaf nodes

C) They visit left and right subtrees in the same order

D) They require different data structures

**Answer: A) They visit the root at different times**

**What is the primary characteristic of level-order traversal?**

A) It visits nodes in a depth-first manner

B) It visits all nodes at the current depth before moving to the next level

C) It requires sorting of nodes

D) It visits nodes in reverse order

**Answer: B) It visits all nodes at the current depth before moving to the next level**

**In which traversal method is the left child visited before the right child?**

A) In-order

B) Pre-order

C) Post-order

D) Both A and B

**Answer: D) Both A and B**

**What would be the output of a post-order traversal for a tree structured as follows: A with left child B and right child C?**

A) A, B, C

B) B, C, A

C) A, C, B

D) C, B, A

**Answer: B) B, C, A**

**Which traversal method is least likely to be used in applications that require sorted output?**

A) In-order

B) Pre-order

C) Post-order

D) None of the above

**Answer: C) Post-order**

**Which traversal method can lead to a full listing of all nodes without regard for order?**

A) In-order

B) Pre-order

C) Post-order

D) Level-order

**Answer: D) Level-order**

**What is the time complexity of tree traversals (in-order, pre-order, post-order)?**

A) O(log n)

B) O(n)

C) O(n log n)

D) O(1)

**Answer: B) O(n)**

**Which traversal would you use to get a prefix expression from an expression tree?**

A) In-order

B) Pre-order

C) Post-order

D) Level-order

**Answer: B) Pre-order**

**What is the output of an in-order traversal on a binary search tree containing the values 3, 1, 4, 2?**

A) 1, 2, 3, 4

B) 3, 4, 2, 1

C) 4, 3, 2, 1

D) 1, 3, 2, 4

**Answer: A) 1, 2, 3, 4**

**What is the primary use of post-order traversal in binary trees?**

A) To create a sorted list

B) To evaluate expressions

C) To copy the tree

D) To delete nodes

**Answer: D) To delete nodes**

**What is the primary advantage of using a stack in tree traversal?**

A) It reduces memory usage

B) It helps maintain the order of visits

C) It allows faster access to nodes

D) It eliminates recursion

**Answer: B) It helps maintain the order of visits**

**Which traversal method requires the use of a queue?**

A) In-order

B) Pre-order

C) Post-order

D) Level-order

**Answer: D) Level-order**

**What is the order of nodes visited in pre-order traversal?**

A) Root, Left, Right

B) Left, Root, Right

C) Left, Right, Root

D) Right, Left, Root

**Answer: A) Root, Left, Right**

**How does post-order traversal affect memory usage?**

A) It uses less memory than in-order

B) It can be implemented without recursion

C) It typically requires more memory for stack

D) It uses constant memory

**Answer: C) It typically requires more memory for stack**

**What traversal method is typically best for creating a balanced tree?**

A) In-order

B) Pre-order

C) Level-order

D) Post-order

**Answer: C) Level-order**

**What is the main difference between depth-first and breadth-first traversal?**

A) The order of node visits

B) The data structure used

C) The time complexity

D) The number of nodes visited

**Answer: A) The order of node visits**

**Which traversal method is suitable for constructing a binary tree from its traversal sequences?**

A) Pre-order and in-order

B) In-order and post-order

C) Level-order and pre-order

D) Any traversal method

**Answer: A) Pre-order and in-order**

**What is the final output of a post-order traversal on a binary tree with nodes A, B, C?**

A) A, B, C

B) B, C, A

C) C, B, A

D) A, C, B

**Answer: B) B, C, A**

**Which traversal method is most intuitive for hierarchical data representation?**

A) In-order

B) Pre-order

C) Post-order

D) Level-order

**Answer: B) Pre-order**

**In the context of binary trees, what does the term “leaf node” refer to?**

A) A node with only one child

B) A node with no children

C) A node that is the root

D) A node with two children

**Answer: B) A node with no children**

**Which traversal method would you use to create a postfix expression?**

A) Pre-order

B) In-order

C) Post-order

D) Level-order

**Answer: C) Post-order**

**How do you recognize the root node during traversal?**

A) It is always visited last

B) It is always visited first in pre-order

C) It is visited in post-order

D) It can be determined by the left child

**Answer: B) It is always visited first in pre-order**

**What is the significance of using recursion in tree traversals?**

A) It simplifies the code structure

B) It increases execution time

C) It uses iterative methods

D) It eliminates stack use

**Answer: A) It simplifies the code structure**

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