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# Data Structure MCQ - Hashing Function

This section focuses on the "Hashing Function" of the Data Structure. These Multiple Choice Questions (mcq) should be practiced to improve the Data Structure skills required for various interviews (campus interview, walk-in interview, company interview), placement, entrance exam and other competitive examinations.

1. What is a hash table?

A. A structure that maps values to keys
B. A structure that maps keys to values
C. A structure used for storage
D. A structure used to implement stack and queue

2. How many different insertion sequences of the key values using the same hash function and linear probing will result in the hash table shown above?

A. 10
B. 20
C. 30
D. 40

3. If ' h ' is a hashing function and it is used to hash ' n ' keys into a table of size ' m ' where n <= m . What is the expected number of collisions involving a particular key ' x ' ?

A. less than 1.
B. less than n.
C. less than m.
D. less than n / 2.

4.Hashing technique which allocates fixed number of buckets is classified as

A. dynamic hashing
B. static hashing
C. external hashing
D. internal hashing

5.If several elements are competing for the same bucket in the hash table, what is it called?

A. Diffusion
B. Replication
C. Collision
D. None of the mentioned

6. Consider a hash table of size seven, with starting index zero, and a hash function (3x + 4)mod7. Assuming the hash table is initially empty, which of the following is the contents of the table when the sequence 1, 3, 8, 10 is inserted into the table using closed hashing? Note that ‘_’ denotes an empty location in the table.

A. 8, _, _, _, _, _, 10
B. 1, 8, 10, _, _, _, 3
C. 1, _, _, _, _, _,3
D. 1, 10, 8, _, _, _, 3

7. What is the advantage of using a dynamic set in direct addressing?

A. It saves time
B. It saves space
C. It saves both time and space
D. None of the mentioned

8. In linear hashing, formula used to calculate number of records if blocking factor, loading factor and file buckets are known is as

A. r =l + bfr + N
B. r =l - bfr - N
C. r =l + bfr - N
D. r =l * bfr * N

9. What is the load factor?

A. Average array size
B. Average key size
C. Average chain length
D. None of the mentioned

10. Given a hash table T with 25 slots that stores 2000 elements, the load factor α for T is __________

A. 80
B. 0.0125
C. 8000
D. 1.25

A. Distinct array position for every possible key
B. Fewer array positions than keys
C. Fewer keys than array positions
D. None of the mentioned

12. What is the search complexity in direct addressing?

A. O(n)
B. O(logn)
C. O(nlogn)
D. O(1)

13. What is a hash function?

A. A function has allocated memory to keys
B. A function that computes the location of the key in the array
C. A function that creates an array
D. None of the mentioned

14. What can be the techniques to avoid collision?

A. Make the hash function appear random
B. Use the chaining method
C. Use uniform hashing
D. All of the mentioned

15. What is simple uniform hashing?

A. Every element has equal probability of hashing into any of the slots
B. A weighted probabilistic method is used to hash elements into the slots
C. All of the mentioned
D. None of the mentioned

16. In simple uniform hashing, what is the search complexity?

A. O(n)
B. O(logn)
C. O(nlogn)
D. O(1)

17. In simple chaining, what data structure is appropriate?

D. Binary trees

18.Which of these are core interfaces in the collection framework. Select the one correct answer.

A. Tree
B. Stack
C. Queue
D. Map

19. Given the following input (4322, 1334, 1471, 9679, 1989, 6171, 6173, 4199) and the hash function x mod 10, which of the following statements are true?

i. 9679, 1989, 4199 hash to the same value
ii. 1471, 6171 hash to the same value
iii. All elements hash to the same value
iv. Each element hashes to a different value

A. i only
B. ii only
C. i and ii only
D. iii or iv

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