Huffman Coding

1. Who introduced Huffman Coding?

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

2. Which type of encoding does Huffman Coding use?

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

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

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

4. What is a prefix code in Huffman Coding?

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

5. What is a Huffman tree also known as?

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

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

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

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

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

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

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

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

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

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

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

11. What kind of codes does Huffman Coding produce?

A) Suffix codes
B) Prefix 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) 1952
C) 1955
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) Queue
B) Array
C) Priority queue
D) Stack

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

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

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

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

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

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

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

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

A) Randomly select an item from either queue
B) Remove both items and start over
C) Choose the item in the second 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) = 2^w_i
B) h(a_i) = w_i * log₂(w_i)
C) h(a_i) = -log₂(w_i)
D) h(a_i) = log₂(1 / w_i)

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

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

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

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

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

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

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

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

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

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

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 only enqueuing nodes with unique weights
D) By randomly selecting nodes from either queue

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

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

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

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

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

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