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# Data Structure MCQ - Threaded Binary Tree

Q1.What is a threaded binary tree traversal?
1. a binary tree traversal using stacks
2. a binary tree traversal using queues
3. a binary tree traversal using stacks and queues
4. a binary tree traversal without using stacks and queues

Explanations :This type of tree traversal will not use stack or queue.
Q2.What are the disadvantages of normal binary tree traversals?
1. there are many pointers which are null and thus useless
2. there is no traversal which is efficient
3. complexity in implementing
4. improper traversals

Explanations :As there are majority of pointers with null value going wasted we use threaded binary trees.
Q3. What is inefficient with the below threaded binary tree picture? 1. it has dangling pointers
2. nothing inefficient
4. space is being used more

Explanations :The nodes extreme left and right are pointing to nothing which could be also used efficiently.
Q4.Which of the following tree traversals work if the null left pointer pointing to the predecessor and null right pointer pointing to the successor in a binary tree?
1. inorder, postorder, preorder traversals
2. inorder
3. postorder
4. preorder

Explanations :In threaded binary trees, the null left pointer points to the predecessor and the right null pointer point to the successor. In threaded binary trees, we can use in-order, preorder and postorder traversals to visit every node in the tree.
Q5.What are the disadvantages of normal binary tree traversals?
1. there are many pointers which are null and thus useless
2. there is no traversal which is efficient
3. complexity in implementing
4. improper traversals

Explanations :As there are majority of pointers with null value going wasted we use threaded binary trees.
Q6.The height of a BST is given as h. Consider the height of the tree as the no. of edges in the longest path from root to the leaf. The maximum no. of nodes possible in the tree is?
1. 2h-1-1
2. 2h+1-1
3. 2h+1
4. 2h-1+1

Q7.The no of external nodes in a full binary tree with n internal nodes is?
1. n
2. n+1
3. 2n
4. 2n + 1

Q8.Suppose we have numbers between 1 and 1000 in a binary search tree and want to search for the number 363. Which of the following sequence could not be the sequence of the node examined?
1. 2, 252, 401, 398, 330, 344, 397, 363
2. 924, 220, 911, 244, 898, 258, 362, 363
3. 925, 202, 911, 240, 912, 245, 258, 363
4. 2, 399, 387, 219, 266, 382, 381, 278, 363

Q9.If a node having two children is to be deleted from binary search tree, it is replaced by its
1. In-order predecessor
2. In-order successor
3. Pre-order predecessor
4. None