Question 1

As the density, or number of keys relative to the length of an array decreases, so does the probability of hashing collisions.

Accepted Answer

A) True 
 B)False

Question 2

For key values of 84 and 108 and a hashing function of key % 12 , what is the result?

Accepted Answer

A)   indexes of 7 and 9
B)   indexes of 0 and 1
C)   a collision
D)   indexes of 12 and 14E) A) and B)
F) A) and C)

Question 3

What strategy does the hashing implementation of a dictionary use?

Accepted Answer

A)   a binary search tree
B)   quadratic probing
C)   linear probing/bucket
D)   bucket/chainingE) C) and D)
F) B) and D)

Question 4

When considering an insertion into a set using a hash function and linear probing, which of the following is defined as the position where the item should go if the has function works perfectly?

Accepted Answer

A)   absolute index
B)   probe index
C)   zero index
D)   home indexE) All of the above
F) A) and B)

Question 5

For a given set s , which method returns True if item is in s , or False otherwise.

Accepted Answer

A)   s.__contains__(item) 
B)   s.__iter__(item) 
C)   s = set() 
D)   S1.__sub__(s2) E) A) and C)
F) C) and D)

Question 6

In Python's dict type, values are inserted or replaced at a given location using the index operator {} .

Accepted Answer

A) True 
 B)False

Question 7

Which method in the interface for a dictionary collection returns an iterator on the key/value pairs in the dictionary?

Accepted Answer

A)   keys() 
B)   entries() 
C)   pairs() 
D)   values() E) B) and D)
F) None of the above

Question 8

The AbstractSet class is a subclass of AbstractCollection because AbstractSet introduces new instance variables for data.

Accepted Answer

A) True 
 B)False

Question 9

The entries in a dictionary consist of a key, a value, and an index.

Accepted Answer

A) True 
 B)False

Question 10

Which of the following is true about sets?

Accepted Answer

A)   the items in a set are arranged in order
B)   the difference and subset operations on a set are symmetric
C)   there are no duplicate items in a set
D)   there is no standard set class in PythonE) None of the above
F) A) and C)

Question 11

In the hashing implementation of a set, the Bag class is used to represent an item and a pointer to the next item in a chain.

Accepted Answer

A) True 
 B)False

Question 12

A hashing function acts on a given key by returning its absolute position in an array.

Accepted Answer

A) True 
 B)False

Question 13

Which of the following is the best array length to reduce the probability of collisions given the set [ 8, 6, 18, 9, 14, 23 ]?

Accepted Answer

A)   9
B)   8
C)   11
D)   12E) A) and B)
F) A) and C)

Question 14

The __sub__ method of the set class returns a set containing items in s1 that are not in s2.

Accepted Answer

A) True 
 B)False

Question 15

Two strings that are anagrams will return a unique integer value when the sum of the ASCII values is calculated.

Accepted Answer

A) True 
 B)False

Question 16

In the hashing implementation of a dictionary, the data field of each node in a chain contains an Entry object.

Accepted Answer

A) True 
 B)False

Question 17

Which statement is true when considering a hashing strategy and the density of the keys/array length relationship?

Accepted Answer

A)   as the density decreases, the probability of collisions decreases
B)   as the density increases, the probability of collisions decreases
C)   as the density decreases, the probability of collisions increases
D)   as the density increases, the probability of collisions stays the sameE) B) and D)
F) C) and D)

Question 18

In the algorithm for the __contains method of the hashing implementation of sets, what is the first step in the algorithm?

Accepted Answer

A)   set foundNode to table[ index ]
B)   set priorNode to foundNode
C)   set index to the home index of the item
D)   set foundNode to foundNode.nextE) A) and C)
F) All of the above

Question 19

If a hashing function runs in constant time, insertions, accesses, and removals of the associated keys are O(1).

Accepted Answer

A) True 
 B)False

Question 20

In the code for the keysToIndexes function, what is the missing code? def keysToIndexes(keys, n) :
Return

Accepted Answer

A)   list(map(lambda key: key % n, keys) ) 
B)   list(map(lambda key: keys, key % n ) ) 
C)   map(list(lambda key: key % n, keys) ) 
D)   map(list(lambda key % n: keys, key) ) E) A) and B)
F) None of the above

Exam 11: Sets and Dictionaries

The __sub__ method of the set class returns a set containing items in s1 that are not in s2.

Correct AnswerverifiedShow Answer

In the algorithm for the __contains method of the hashing implementation of sets, what is the first step in the algorithm?

Correct AnswerverifiedShow Answer

In the code for the keysToIndexes function, what is the missing code? def keysToIndexes(keys, n) : Return < missing code >

Correct AnswerverifiedShow Answer

For a given set s , which method returns True if item is in s , or False otherwise.

Correct AnswerverifiedShow Answer

A hashing function acts on a given key by returning its absolute position in an array.

Correct AnswerverifiedShow Answer

In the hashing implementation of a dictionary, the data field of each node in a chain contains an Entry object.

Correct AnswerverifiedShow Answer

Which of the following is the best array length to reduce the probability of collisions given the set [ 8, 6, 18, 9, 14, 23 ]?

Correct AnswerverifiedShow Answer

In the hashing implementation of a set, the Bag class is used to represent an item and a pointer to the next item in a chain.

Correct AnswerverifiedShow Answer

Which method in the interface for a dictionary collection returns an iterator on the key/value pairs in the dictionary?

Correct AnswerverifiedShow Answer

In Python's dict type, values are inserted or replaced at a given location using the index operator {} .

Correct AnswerverifiedShow Answer

If a hashing function runs in constant time, insertions, accesses, and removals of the associated keys are O(1).

Correct AnswerverifiedShow Answer

Which of the following is true about sets?

Correct AnswerverifiedShow Answer

When considering an insertion into a set using a hash function and linear probing, which of the following is defined as the position where the item should go if the has function works perfectly?

Correct AnswerverifiedShow Answer

For key values of 84 and 108 and a hashing function of key % 12 , what is the result?

Correct AnswerverifiedShow Answer

The AbstractSet class is a subclass of AbstractCollection because AbstractSet introduces new instance variables for data.

Correct AnswerverifiedShow Answer

The entries in a dictionary consist of a key, a value, and an index.

Correct AnswerverifiedShow Answer

Two strings that are anagrams will return a unique integer value when the sum of the ASCII values is calculated.

Correct AnswerverifiedShow Answer

What strategy does the hashing implementation of a dictionary use?

Correct AnswerverifiedShow Answer

As the density, or number of keys relative to the length of an array decreases, so does the probability of hashing collisions.

Correct AnswerverifiedShow Answer

Which statement is true when considering a hashing strategy and the density of the keys/array length relationship?

Correct AnswerverifiedShow Answer

The sub method of the set class returns a set containing items in s1 that are not in s2.

Correct Answer
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