Comp Sci Unit 3 #9

The following grid contains a robot represented as a triangle, which is initially facing right.

The following code segment is intended to move the robot to the gray square.

<MISSING STATEMENT>

{

REPEAT 4 TIMES

{

MOVE_FORWARD()

ROTATE_RIGHT()

}

ROTATE_LEFT()

MOVE_FORWARD()

ROTATE_RIGHT()

}

Which of the following can be used as a replacement for <MISSING STATEMENT> so that the code segment works as intended?

• REPEAT 1 TIMES

• REPEAT 2 TIMES

• REPEAT 3 TIMES

• REPEAT 4 TIMES

The following grid contains a robot represented as a triangle, which is initially facing toward the top of the grid. The robot can move into a white or gray square but cannot move into a black region.

Which of the following code segments can be used to move the robot to the gray square?

Responses

• REPEAT 3 TIMES

  {

  MOVE_FORWARD()

  }

  REPEAT 2 TIMES

  {

  MOVE_FORWARD()

  }

  REPEAT 3 TIMES

  {

  MOVE_FORWARD()

  }

• REPEAT 8 TIMES

  {

  MOVE_FORWARD()

  }

• REPEAT 3 TIMES

  {

  MOVE_FORWARD()

  }

  ROTATE_LEFT()

  REPEAT 2 TIMES

  {

  MOVE_FORWARD()

  }

  ROTATE_LEFT()

  REPEAT 3 TIMES

  {

  MOVE_FORWARD()

  }

• REPEAT 3 TIMES

  {

  MOVE_FORWARD()

  }

  ROTATE_LEFT()

  REPEAT 2 TIMES

  {

  MOVE_FORWARD()

  }

  ROTATE_RIGHT()

  REPEAT 3 TIMES

  {

  MOVE_FORWARD()

  }

A teacher stores the most recent quiz scores for her class in the list scores. The first element in the list holds the maximum possible number of points that can be awarded on the quiz, and each remaining element holds one student’s quiz score. Assume that scores contains at least two elements. Which of the following code segments will set the variable found to true if at least one student scored the maximum possible number of points on the quiz and will set found to false otherwise?

• 
• 
• 
• 

The grid below contains a robot represented as a triangle, initially facing toward the top of the grid. The robot can move into a white or gray square but cannot move into a black region.

The code segment below uses the procedure goalReached, which evaluates to true if the robot is in the gray square and evaluates to false otherwise.

REPEAT UNTIL(goalReached())

{

<MISSING CODE>

}

Which of the following replacements for <MISSING CODE> can be used to move the robot to the gray square?

• IF(CAN_MOVE(left))

  {

  ROTATE_LEFT()

  MOVE_FORWARD()

  }

• IF(CAN_MOVE(forward))

  {

  MOVE_FORWARD()

  ROTATE_LEFT()

  }

• IF(CAN_MOVE(left))

  {

  ROTATE_LEFT()

  }

  MOVE_FORWARD()

• IF(CAN_MOVE(forward))

  {

  MOVE_FORWARD()

  }

  ELSE

  {

  ROTATE_LEFT()

  }

Consider the following code segment.

theList ← [-2, -1, 0, 1, 2]

count1 ← 0

count2 ← 0

FOR EACH value IN theList

{

IF(value > 0)

{

count1 ← count1 + 1

}

ELSE

{

count2 ← count2 + 1

}

}

What are the values of count1 and count2 as a result of executing the code segment?

• count1 = 2, count2 = 2

• count1 = 2, count2 = 3

• count1 = 3, count2 = 2

• count1 = 5, count2 = 0

Consider the following code segment.

What is displayed as a result of executing the code segment?

• 1 3 5

• 5 3 1

• 100 300 500

• 500 300 100

Consider the following code segment.

What value is displayed as a result of executing the code segment?

• 3

• 4

• 9

• 
  12

The procedure below searches for the value target in list. It returns true if target is found and returns false otherwise.

Which of the following are true statements about the procedure?

I. It implements a binary search.

II. It implements a linear search.

III. It only works as intended when list is sorted.

• I only

• II only

• I and III

• II and III

The question below uses a robot in a grid of squares. The robot is represented as a triangle, which is initially in the bottom left square of the grid and facing right.

The following programs are each intended to move the robot to the gray square. Program II uses the procedure GoalReached, which returns true if the robot is in the gray square and returns false otherwise.
Which of the following statements best describes the correctness of the programs?

• Program I correctly moves the robot to the gray square, but program II does not.

• Program II correctly moves the robot to the gray square, but program I does not.

• Both program I and program II correctly move the robot to the gray square.

• Neither program I nor program II correctly moves the robot to the gray square.

The following question uses a robot in a grid of squares. The robot is represented as a triangle, which is initially facing toward the top of the grid.

The following code segment moves the robot around the grid. Assume that n is a positive integer.

Line 1: count ← 0

Line 2: REPEAT n TIMES

Line 3: {

Line 4:    REPEAT 2 TIMES

Line 5:    {

Line 6:       MOVE_FORWARD()

Line 7:    }

Line 8:    ROTATE_RIGHT()

Line 9: }

Consider the goal of modifying the code segment to count the number of squares the robot visits before execution terminates. Which of the following modifications can be made to the code segment to correctly count the number of squares the robot moves to?

• Inserting the statement count ← count + 1 between line 6 and line 7

• Inserting the statement count ← count + 2 between line 6 and line 7

• Inserting the statement count ← count + 1 between line 8 and line 9

• Inserting the statement count ← count + n between line 8 and line 9