Hash Functions and Hash Tables: Master Hashing and Collision Resolution

Question 1

Which collision resolution technique involves storing multiple values in the same hash table slot?

Accepted Answer

Chaining

Answer

Open addressing

Answer

Double hashing

Answer

Quadratic probing

Question 2

Consider a hash table of size 10 using the hash function h(k) = k % 10. What is the hash value for the key 25?

Accepted Answer

5

Answer

10

Answer

15

Answer

20

Question 3

Which advantage does using separate chaining offer as a collision resolution technique?

Accepted Answer

Efficient insertion and deletion of elements

Answer

No need to resize the hash table

Answer

Guaranteed constant-time lookup

Answer

Improved performance for large hash tables

Question 4

What is the primary purpose of a load factor in a hash table?

Accepted Answer

To determine when the hash table requires resizing

Answer

To enhance hash table performance by modifying the number of slots

Answer

To minimize the occurrence of collisions

Answer

To ensure the hash table remains full at all times

Question 5

Which of the following is a potential drawback of employing open addressing as a collision resolution technique?

Accepted Answer

Increased likelihood of primary clustering

Answer

Frequent need for hash table resizing

Answer

Slow insertion and deletion operations

Answer

Limited space for storing values

Question 6

What advantage does the separate chaining approach offer for resolving hash collisions?

Accepted Answer

Minimizes the impact of collisions on retrieval efficiency.

Answer

Eliminates the possibility of infinite looping.

Answer

Requires less memory overhead compared to other techniques.

Answer

Ensures uniform distribution of data across all hash buckets.

Question 7

Assuming a good hash function and a constant average cost of resolving collisions, what is the expected time complexity of searching for a key in a hash table with n elements?

Accepted Answer

O(1)

Answer

O(n)

Answer

O(log n)

Answer

O(n^2)

Question 8

What is the purpose of a load factor in a hash table?

Accepted Answer

To determine when the hash table needs to be resized to prevent collisions

Answer

To measure the efficiency of the hash function

Answer

To optimize the search time for a given key

Answer

To prevent data loss during hash collisions

Question 9

Which of the following is not a collision resolution technique used in hash tables?

Accepted Answer

Sorting the hash table

Answer

Chaining

Answer

Linear probing

Answer

Double hashing

Question 10

Distinguish double hashing from linear probing and quadratic probing, emphasizing its advantages.

Accepted Answer

Double hashing employs two hash functions, unlike linear probing and quadratic probing which use only one.

Accepted Answer

Double hashing effectively reduces data clustering compared to linear probing and quadratic probing.

Answer

Double hashing is not inherently easier to implement than linear probing or quadratic probing.

Question 11

Which of the following is NOT a benefit of using hash functions?

Accepted Answer

Minimized storage space requirements

Answer

Faster data retrieval

Answer

Reduced search time complexity

Answer

Improved data organization

Question 12

In a hash table, what occurs when two keys have the same hash value?

Accepted Answer

A collision

Answer

An overflow

Answer

A segmentation fault

Answer

A runtime error

Question 13

What is the primary function of a hash table?

Accepted Answer

To store and retrieve data efficiently using key-value pairs

Answer

To generate unique identifiers for data elements

Answer

To sort data in ascending or descending order

Answer

To compress data for storage

Question 14

What is the load factor of a hash table?

Accepted Answer

The ratio of the number of keys to the number of slots in the table

Answer

The number of collisions that occur in the table

Answer

The average time required to retrieve a value from the table

Answer

The maximum number of keys that can be stored in the table

Question 15

What is the key difference between open addressing and closed addressing in hash tables?

Accepted Answer

Open addressing allows for collisions, while closed addressing does not

Answer

Open addressing uses a linked list for collision resolution, while closed addressing uses a separate overflow area

Answer

Open addressing is faster than closed addressing

Answer

Closed addressing is more memory-efficient than open addressing

Question 16

What is the purpose of the modulo operator in a hash function?

Accepted Answer

To ensure that the hash value falls within the range of the hash table

Answer

To improve the uniformity of hash value distribution

Answer

To reduce the number of collisions

Answer

To increase the speed of hash value computation

Question 17

Which of the following is NOT a primary purpose of hash functions?

Accepted Answer

To ensure uniqueness of data elements

Answer

To condense a large data set into a smaller, fixed-size space

Answer

To handle collisions effectively

Answer

To accelerate insertion and retrieval of data

Question 18

In the context of hash tables, what is the process of managing hash collisions called?

Accepted Answer

Collision resolution

Answer

Hashing

Answer

Data storage

Answer

Hash table creation

Question 19

Which collision resolution technique involves creating a linked list for each colliding key in a hash table?

Accepted Answer

Chaining

Answer

Quadratic probing

Answer

Linear probing

Answer

Double hashing

Question 20

In the context of hash tables, what is the primary purpose of a load factor?

Accepted Answer

To determine when to resize the hash table

Answer

To represent the average number of elements per bucket

Answer

To optimize collision resolution

Answer

To prevent hash collisions

Question 21

In a hash table, what is the primary data structure used to store key-value pairs?

Accepted Answer

Array

Answer

Linked list

Answer

Tree

Answer

Graph

Question 22

Which of the following operations is generally faster in a hash table compared to a binary search tree?

Accepted Answer

Searching for an element

Answer

Inserting an element

Answer

Deleting an element

Answer

Traversing the structure

Question 23

What is the term for the process of distributing elements from a hash table into a new hash table with a different size?

Accepted Answer

Rehashing

Answer

Resizing

Answer

Remapping

Answer

Rebalancing

Question 24

Which collision resolution technique allows for efficient search times even when the hash table is full, potentially requiring additional memory?

Accepted Answer

Chaining

Answer

Linear Probing

Question 25

Which property is NOT essential for an ideal hash function?

Accepted Answer

Prevents collisions entirely

Answer

Computes distinct values for all keys

Answer

Distributes keys uniformly across the hash table

Answer

Executes efficiently

Question 26

In a hash table with a load factor of 1, what is the status of its slots?

Accepted Answer

No unoccupied slots

Answer

Multiple elements within each slot

Answer

Equal distribution of occupied and unoccupied slots

Answer

More unoccupied slots than occupied slots

Question 27

Which of the following is NOT a primary purpose of a hash table?

Accepted Answer

Large dataset compression

Answer

Efficient data storage and retrieval

Answer

Collision resolution in hash functions

Answer

缩小数据项搜索范围

Question 28

In an optimal scenario, what is the time complexity of both insertion and search operations in a hash table?

Accepted Answer

O(1) for both insertion and search

Answer

O(n) for insertion and O(1) for search

Answer

O(log n) for both insertion and search

Answer

O(n^2) for both insertion and search

Question 29

What is the process of determining an appropriate size for a hash table referred to as?

Accepted Answer

Load factor calculation

Answer

Hashing

Answer

Collision resolution

Answer

Indexing

Question 30

In a hash table with chaining as the collision resolution technique, what would lead to the worst-case performance?

Accepted Answer

When the hash table is nearly full

Answer

When the hash table is empty

Answer

When the hash function distributes data evenly

Answer

When the load factor is low

Question 31

Which of the following is NOT an advantage of using a hash table?

Accepted Answer

Ability to maintain sorted data

Answer

Efficient lookup and retrieval operations

Answer

Efficient handling of large datasets

Answer

Reduced memory usage

Question 32

To minimize collisions in a hash table, which factor is crucial when designing a hash function?

Accepted Answer

Even distribution and randomization

Answer

Minimizing computational complexity

Answer

Adapting to specific data types

Answer

Enhancing security features

Question 33

What is the primary purpose of a hash table?

Accepted Answer

To store key-value pairs for efficient retrieval

Answer

To sort data in ascending order

Answer

To search for data in a binary tree

Answer

To implement a queue

Question 34

Which collision resolution technique involves linking multiple values together at the same hash index?

Accepted Answer

Chaining

Answer

Linear probing

Answer

Quadratic probing

Answer

Double hashing

Question 35

What is the formula for calculating the load factor of a hash table?

Accepted Answer

The ratio of stored values to the total number of hash slots

Answer

The number of hash functions used

Answer

The maximum number of values that can be stored

Answer

The size of the hash table in bytes

Question 36

In the context of hash tables, what is the key difference between open addressing and closed addressing?

Accepted Answer

With open addressing, multiple values can occupy the same hash slot, while with closed addressing, they cannot.

Answer

With closed addressing, multiple values can occupy the same hash slot, while with open addressing, they cannot.

Answer

Open addressing is generally more efficient than closed addressing.

Answer

Closed addressing is generally more efficient than open addressing.

Question 37

What is the purpose of a Bloom filter?

Accepted Answer

A probabilistic data structure used for efficient set membership testing

Answer

A type of hash function that guarantees no collisions

Answer

A data structure for storing key-value pairs in ascending order

Answer

An algorithm for finding the shortest path in a weighted graph

Question 38

Which collision resolution technique utilizes an additional data structure, such as a linked list, to manage hash collisions?

Accepted Answer

Chaining

Answer

Linear probing

Answer

Double hashing

Question 39

Which of the following is an essential property of a well-designed hash function?

Accepted Answer

It distributes the input values uniformly across the output range, minimizing collisions.

Answer

It generates the same hash value for all input values.

Answer

It is computationally inexpensive to evaluate.

Question 40

Define a hash table.

Accepted Answer

A data structure that utilizes a hash function to efficiently map keys to their associated values.

Answer

A tree-like structure that organizes data in nodes.

Answer

A sorted array of key-value pairs.

Question 41

Assuming a perfectly designed hash function and m elements, what is the time complexity of searching for a key in a hash table?

Accepted Answer

O(1)

Answer

O(m^2)

Answer

O(m)

Answer

O(log m)

Question 42

What is the load factor of a hash table?

Accepted Answer

The ratio of the number of elements to the number of buckets in the table.

Answer

The average number of elements stored in each bucket.

Answer

The number of collisions that have occurred in the table.

Question 43

When is it generally recommended to resize a hash table?

Accepted Answer

When the load factor exceeds a predetermined threshold, typically to maintain optimal performance.

Answer

When the table becomes unbalanced.

Answer

Never

Answer

When the number of elements exceeds a certain threshold.

Question 44

Which of the following is not a potential disadvantage of using hash tables?

Accepted Answer

They are generally suitable for storing various data types.

Answer

Their performance can be significantly impacted by poorly designed hash functions.

Answer

They require additional memory to store both keys and values.

Answer

They are susceptible to hash collisions.

Question 45

What is the primary objective of a universal hashing function?

Accepted Answer

To minimize the likelihood of hash collisions for any given set of input values.

Answer

To generate a unique hash value for every possible input value.

Answer

To evenly distribute the input values across the output range.

Question 46

What defines a perfect hash function?

Accepted Answer

It maps all keys to unique, distinct values, eliminating collisions.

Answer

It effectively resolves collisions that occur.

Answer

It requires a large hash table to function properly.

Question 47

What is the primary purpose of a hash table?

Accepted Answer

To store and retrieve key-value pairs efficiently using a hash function for mapping keys to memory locations.

Answer

To organize data into a binary tree structure for efficient searching.

Answer

To divide data into smaller segments for faster access.

Question 48

Which of these is a common technique to resolve collisions in a hash table?

Accepted Answer

Linear probing

Answer

Greedy algorithm (a general problem-solving technique)

Answer

Bubble sort (a sorting algorithm)

Answer

Breadth-first search (a graph traversal algorithm)

Question 49

How is the load factor of a hash table calculated?

Accepted Answer

By dividing the number of stored elements by the total size of the hash table.

Answer

By dividing the number of collisions by the number of elements.

Answer

By averaging the number of elements in each bucket.

Question 50

What is NOT a drawback associated with closed addressing (open hashing) in hash tables?

Accepted Answer

No wasted space is required.

Answer

Primary clustering can occur, where collisions form in a specific area of the table.

Answer

Search time can increase significantly with high load factors.

Answer

It can lead to secondary clustering, where collisions form groups.

Question 51

In a well-designed hash table, what is the typical time complexity for searching an element?

Accepted Answer

O(1) - constant time

Answer

O(n) - linear time

Answer

O(log n) - logarithmic time

Answer

O(n^2) - quadratic time

Question 52

What is a key advantage of using double hashing as a collision resolution method?

Accepted Answer

It reduces both primary and secondary clustering, making the distribution of elements more even.

Answer

It handles collisions more efficiently than linear probing in every case.

Answer

It guarantees superior search performance in all situations.

Answer

It completely eliminates the need for extra space in the hash table.

Question 53

When is a hash table considered 'full' in practical terms?

Accepted Answer

When the load factor reaches a predefined threshold, indicating potential performance degradation.

Answer

When all the buckets are completely occupied by elements.

Answer

When the number of elements stored exceeds the exact size of the hash table.

Question 54

What is a crucial consideration during the design of a hash function?

Accepted Answer

The hash function should produce a uniform distribution of hash values, minimizing collisions.

Answer

The speed of computation is the most important factor.

Answer

The ease of implementation is the top priority.

Answer

The primary goal is to completely avoid any collisions.

Question 55

Which of the following best describes the key applications of hash tables?

Accepted Answer

They are widely used for database indexing, caching systems, and efficient set operations.

Answer

They are mainly used in natural language processing, machine learning, and artificial intelligence.

Answer

They are primarily used for sorting large datasets, searching unordered lists, and graph traversal.

Answer

Their primary applications lie in image processing, numerical analysis, and cryptography.