Huffman Coding

1. Who introduced Huffman Coding?

A) John Smith
B) Alice Jones
C) Robert Johnson
D) David A. Huffman

2. Which type of encoding does Huffman Coding use?

A) ASCII encoding
B) Variable-length encoding
C) Binary encoding
D) Fixed-length encoding

3. In Huffman Coding, what type of symbols have shorter codes?

A) Symbols starting with A
B) Symbols at odd indices
C) Rare symbols
D) Frequent symbols

4. What is a prefix code in Huffman Coding?

A) A code that starts with the same symbol
B) A code with equal-length codewords
C) A code that uses only 0s and 1s
D) A code where no codeword is a prefix of another

5. What is a Huffman tree also known as?

A) Perfect tree
B) Optimal binary tree
C) Balanced tree
D) Complete tree

6. How is the efficiency of Huffman Coding usually measured?

A) Compression ratio
B) Encoding speed
C) Memory consumption
D) Number of symbols

7. What's the worst-case time complexity of building a Huffman tree?

A) O(n log n)
B) O(n)
C) O(n²)
D) O(log n)

8. Which step comes after building the Huffman tree in the encoding process?

A) Assigning binary codes to symbols
B) Calculating symbol frequencies
C) Compressing the data
D) Building a linked list

9. In Huffman Coding, what symbol is typically assigned the shortest code?

A) Symbol with the longest name
B) Symbol with a prime number
C) Least frequent symbol
D) Most frequent symbol

10. Which data structure is commonly used to implement a priority queue in Huffman Coding?

A) Queue
B) Binary heap
C) Linked list
D) Stack

11. What kind of codes does Huffman Coding produce?

A) Prefix codes
B) Suffix codes
C) Infix codes
D) Postfix codes

12. In which year was the paper 'A Method for the Construction of Minimum-Redundancy Codes' published?

A) 1949
B) 1955
C) 1952
D) 1960

13. Which data structure is used for efficient insertion and retrieval of nodes by probability in a simple Huffman tree construction algorithm?

A) Array
B) Priority queue
C) Stack
D) Queue

14. What is a common use of modified Huffman coding?

A) Image encoding for web pages.
B) Text compression in word processors.
C) Audio file compression.
D) Fax machines.

15. Which university was David A. Huffman attending when he developed the algorithm?

A) MIT
B) Princeton University
C) Stanford University
D) Harvard University

16. What happens to the two nodes with the smallest probability during Huffman tree construction?

A) They become root nodes
B) They remain as leaf nodes
C) They are combined into a new internal node
D) They are removed from the tree

17. In the linear-time Huffman tree construction, where are initial weights enqueued?

A) Both queues simultaneously
B) The first queue
C) The second queue
D) Neither queue

18. What is the formula for entropy H(A)?

A) H(A) = ∑(w_i > 0) log₂(w_i)
B) H(A) = -∑(w_i > 0) w_i * log₂(w_i)
C) H(A) = ∑(w_i > 0) h(a_i) / w_i
D) H(A) = ∑(w_i > 0) w_i / log₂(w_i)

19. How do you break ties between queues to minimize variance in Huffman coding?

A) Choose the item in the second queue
B) Remove both items and start over
C) Randomly select an item from either queue
D) Choose the item in the first queue

20. How is the information content h(a_i) of a symbol ai defined?

A) h(a_i) = w_i * log₂(w_i)
B) h(a_i) = -log₂(w_i)
C) h(a_i) = log₂(1 / w_i)
D) h(a_i) = 2^w_i

21. What kind of problems can Huffman template algorithms solve?

A) Only compression-related problems.
B) Minimizing the maximum weighted path length, among others.
C) Problems that do not involve weights.
D) Problems related to sorting data.

22. Which method can replace Huffman coding if a better compression ratio is required?

A) Shannon-Fano coding
B) Lempel-Ziv-Welch (LZW)
C) Run-length encoding
D) Arithmetic coding

23. What does bit '0' represent in a Huffman tree?

A) Following the right child
B) A leaf node
C) Following the left child
D) An internal node

24. Who solved the Huffman coding problem with unequal letter costs?

A) Alan Turing.
B) T. C. Hu.
C) Adriano Garsia.
D) Richard M. Karp.

25. What is required when using Huffman coding with unknown input probabilities?

A) A frequency table must be stored with the compressed text.
B) An encryption key must accompany the compressed data.
C) The original text must be stored alongside the compressed version.
D) No additional information needs to be stored.

26. When constructing a Huffman tree using two queues, how do you ensure the lowest weight is always at the front?

A) By keeping initial weights in the first queue and combined weights in the second queue
B) By sorting both queues by weight after each insertion
C) By randomly selecting nodes from either queue
D) By only enqueuing nodes with unique weights

27. What algorithm solves the problem of length-limited Huffman coding?

A) Adaptive Huffman algorithm.
B) Template Huffman algorithm.
C) Binary Huffman algorithm.
D) The package-merge algorithm.

28. What is the contribution of a symbol with zero probability to entropy?

A) It is equal to the symbol's information content
B) Zero, since lim_(w→0+) w * log₂(w) = 0
C) It equals the inverse of its weight
D) It contributes negatively to the entropy

29. How many queues are used in the linear-time method to create a Huffman tree?

A) Four
B) One
C) Two
D) Three

30. In alphabetic Huffman coding, what must be identical between inputs and outputs?

A) The transmission cost.
B) The frequency of occurrence.
C) The alphabetic order.
D) The binary representation.

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