Data Structures 4

Question 1

A stack s, a queue q, and a max value priority queue p each have a single 3 in them. Next s.push(4), q.push(4), and p.push(4) are executed.

What is the triple (s.pop(), q.pop(), p.pop())?

Answer 1

(4,3,4)

Question 2

This stack reads left to right with the top to the right:
‘green’
‘yellow’
‘blue’
‘red’

What could be the stack after a push operation?

Answer 2

[‘red’,’blue’,’yellow’, ‘green’, ‘purple”]

Question 3

Items were added sequentially onto the stack starting with ‘red’:
‘green’
‘yellow’
‘blue’
‘red’

What is the stack after a pop operation?

Answer 3

‘yellow’
‘blue’
‘red’

Question 4

Which command helps to speed up comparisons using dictionary keys during a dictionary (d) lookup in this pseudocode clip?

h = hash(key)
for pair in d:
if h == pair[0]:
return pair[1]

Answer 4

hash(object)

Question 5

What does the method any(b) return in Python if b is a dictionary?

Answer 5

Returns True if any key of the dictionary is true.

Question 6

Which Java method is used to read bytes from a standard file?

Answer 6

Java.io.FileInputStream

Question 7

Which command will retrieve an item from the top of the stack?

Answer 7

Pop()

Question 8

Which command will insert object x at position index in a list?

Answer 8

Add(int index, Object x)

Question 9

Which command will return true if x is in a list, otherwise return false?

Answer 9

Contains(Object x)

Question 10

When should a dictionary be used instead of a list?

Answer 10

When the program uses key-value pairs as its data