Engineering Questions with Answers - Multiple Choice Questions

# Hash Tables with Linear Probing MCQ’s

1 - Question

Which of the following problems occur due to linear probing?
a) Primary collision
b) Secondary collision
c) Separate chaining
d) Extendible hashing

Explanation: Primary collision occurs due to linear probing technique. It is overcome using a quadratic probing technique.

2 - Question

How many probes are required on average for insertion and successful search?
a) 4 and 10
b) 2 and 6
c) 2.5 and 1.5
d) 3.5 and 1.5

Explanation: Using formula, the average number of probes required for insertion is 2.5 and for a successful search, it is 1.5.

3 - Question

a) 1
b) 0.5
c) 1.5
d) 0

Explanation: The load factor for an open addressing technique should be 0.5. For separate chaining technique, the load factor is 1.

4 - Question

Which of the following is not a collision resolution strategy for open addressing?
a) Linear probing
c) Double hashing
d) Rehashing

Explanation: Linear probing, quadratic probing and double hashing are all collision resolution strategies for open addressing whereas rehashing is a different technique.

5 - Question

In linear probing, the cost of an unsuccessful search can be used to compute the average cost of a successful search.
a) True
b) False

Explanation: Using random collision resolution algorithm, the cost of an unsuccessful search can be used to compute the average cost of a successful search.

6 - Question

Which of the following is the correct function definition for linear probing?
a) F(i)= 1
b) F(i)=i
c) F(i)=i2
d) F(i)=i+1

Explanation: The function used in linear probing is defined as, F(i)=I where i=0,1,2,3….,n.

7 - Question

_________ is not a theoretical problem but actually occurs in real implementations of probing.
a) Hashing
b) Clustering
c) Rehashing
d) Collision

Explanation: Clustering is not a theoretical problem but it occurs in implementations of hashing. Rehashing is a kind of hashing.

8 - Question

What is the hash function used in linear probing?
a) H(x)= key mod table size
b) H(x)= (key+ F(i2)) mod table size
c) H(x)= (key+ F(i)) mod table size
d) H(x)= X mod 17

Explanation: The hash function used in linear probing is defined to be H(x)= (key+ F(i)) mod table size where i=0,1,2,3,…,n.

9 - Question

Hashing can be used in online spelling checkers.
a) True
b) False

Explanation: If misspelling detection is important, an entire dictionary can be pre-hashed and words can be checked in constant time.

10 - Question

In the following given hash table, use linear probing to find the location of 49.

 0 1 2 3 4 5 6 7 8 18 9 89

a) 7
b) 6
c) 2
d) 0

Explanation: Initially, collision occurs while hashing 49 for the first time.
Hence, after setting f(i)=1, the hashed location is found to be 0.

11 - Question

What is the formula to find the expected number of probes for an unsuccessful search in linear probing?
a) $$\frac{1}{2} \frac{1+1}{(1-⅄)}$$
b) $$\frac{1}{2}\frac{1+1}{(1-⅄)^2}$$
c) $$\frac{1}{2}\frac{1+1}{(1+⅄)}$$
d) $$\frac{1}{2}\frac{1+1}{(1+⅄)(1-⅄)}$$

Explanation: The mathematical formula for calculating the number of probes for an unsuccessful search is $$\frac{1}{2}\frac{1+1}{(1-⅄)^2}$$. For insertion, it is $$\frac{1}{2} \frac{1+1}{(1-⅄)}$$.