DSL Placement Paper - Data Structure Questions And Answers

DSL Previous Years Solved Sample Placement Papers

1. In a B+ tree, both the internal nodes and the leaves have keys.

   A) True

   B) False (Ans)

   Explanation: In a B+ -tree, only the leaves have keys, and these keys are replicated in non-leaf nodes for defining the path for locating individual records.

2. Which of the following is true?

   A) B + tree allows only the rapid random access

   B) B + tree allows only the rapid sequential access

   C) B + tree allows rapid random access as well as rapid sequential access (Ans)

   D) B + tree allows rapid random access and slower sequential access

   Explanation: The B+ -tree being a variation of B-tree allows rapid random access. In a B+ -tree, the leaves are linked together, so it also provides rapid sequential access.

3. A B+ tree can contain a maximum of 7 pointers in a node. What is the minimum number of keys in leaves?

   A) 6

   B) 3 (Ans)

   C) 4

   D) 7

   Explanation: Maximum number of pointers in a node is 7, i.e., the order of the B+ -tree is 7. In a B+ tree of order n, each leaf node contains at most n – 1 keys and at least ⌈(n − 1)/2⌉ keys. Therefore, a minimum number of keys each leaf can have = ⌈(7 – 1)/2⌉ = 3.

4. Which of the following is false?

   A) A B+ -tree grows downwards

   B) A B+ -tree is balanced

   C) In a B+ -tree, the sibling pointers allow sequential searching

   D) B+ -tree is shallower than B-tree

   (Ans) A) A B+ -tree grows downwards.

5. When a node is split during insertion, the middle key is promoted to the parent as well as retained in the right half-node. When a key is deleted from the leaf, it is also deleted from the non-leaf nodes of the tree.

   A) Statement 1 is true but statement 2 is false (Ans)

   B) Statement 2 is true but statement 1 is false

   C) Both the statements are true

   D) Both the statements are false

   Explanation: During the split, the middle key is retained in the right half node and also promoted to the parent node. When a key is deleted from the leaf, it is retained in non-leaves because it can still be a valid separator between keys in nodes below.

6. Efficiency of finding the next record in a B+ tree is ____.

   A) O(n)

   B) O(log n)

   C) O(n log n)

   D) O(1) (Ans)

   Explanation: In a B+ -tree, finding the next record (successor) involves accessing an additional leaf at most. So, the efficiency of finding the next record is O(1).

7. What is the maximum number of keys that a B+ -tree of order 3 and of height 3 can have?

   A) 3

   B) 80

   C) 27

   D) 26 (Ans)

   Explanation: A B+ tree of order n and height h can have at most n^h – 1 keys. Therefore, the maximum number of keys = 3³ - 1 = 27 - 1 = 26.

8. Which of the following is false?

   A) Compared to B-tree, B+ -tree has larger fanout

   B) Deletion in B-tree is more complicated than in B+ -tree

   C) B+ -tree has greater depth than the corresponding B-tree

   D) Both B-tree and B+ -tree have the same search and insertion efficiencies

   (Ans) C) B+ -tree has greater depth than the corresponding B-tree.

   Explanation: A B+ -tree has a larger fanout and therefore has a depth smaller than that of the corresponding B-tree.