Unit 2: Abstraction, Algorithms, List

Consider the following code segment:

myList ← ["red", "yellow", "green", "blue"]

X ← <MISSING CODE>

DISPLAY(X)

What should <MISSING CODE> be replaced with so that “yellow” is displayed after executing the code?

• [2]myList

• myList[2]

• myList[“yellow”]

• “yellow”[myList]

Consider the following code segment:

numberList ← [2, 5, 8, 1]

X ← numberList[1] + numberList[3]

DISPLAY(X)

What will be displayed after executing the code segment?

• 10

• 7

• 13

• 3

Consider the following code segment:

words ← [“hello”, “bye”, “no”, “yes”]

Which of the following is a valid index for the list, words?

• 5

• -1

• "bye"

• 4

A programmer is writing a sports program that handles football teams and their players. Which of the following is the most appropriate data type to represent a collection of different football player’s names?

• String

• Boolean

• Numeric

• List

Consider the following code segment:

firstList ← ["apple", "banana", "orange"]

secondList ← ["grape", "lemon"]

thirdList ← []

thirdList ← firstList

firstList ← secondList

secondList ← thirdList

What are the contents of secondList after the code segment is executed?

• [ ]

• ["apple", "banana", "orange"]

• ["grape", "lemon"]

• ["apple", "banana", "orange", "grape", "lemon"]

Consider the following code segment:

numbersList ← [8, 6, 2, 1]

APPEND ( numbersList , 4 )

X ← numbersList[1]

Y ← numbersList[5]

Z ← X MOD Y

DISPLAY (Z)

What displays after the code segment is executed?

• 4

• 0

• 3

• 1

Which of the following is a benefit of using a list as a data abstraction in a program?

• Lists often allow their size to be easily updated to hold as many data values as needed.

• Lists convert all elements to strings so that they can be inspected character-by-character.

• Lists prevent duplicate data values from appearing in the list.

• Lists are used to store all input data so that there is a running record of all user input.

A programmer is creating a program that will add two user inputs together and display the sum to the user. Which of the following would be an appropriate algorithm?

• Ask the user for inputs. Display the output.

• Ask the user for inputs. Store the inputs into variables. Calculate the sum of the two variables. Display the sum.

• Add the numbers together. Display the numbers.

• Add numbers together. Store user input into variables. Display the numbers.

A student is creating a program that will calculate the average for her friends’ grades. Which of the following would be an appropriate algorithm?

• Create a list for grades, ask the user for input, store the user input into the list, calculate the average of the list, return to the user

• Ask the user for input, store the user input into the list, calculate the average of the list, create the list for grades

• Create a list for grades, return the output to the user, ask the user for input, calculate the average of the list,

• Ask the user for input, return to the user, create the list for grades, calculate the average for the list

colors ← ["red", "yellow", "green", "blue"]

DISPLAY( LENGTH (colors) )

• 4

• 5

• 3

• 2