3.9 Developing Algorithms

Consider the following code segment with an integer variable num. IF(num > 0) { DISPLAY("positive") } IF(num < 0) { DISPLAY("negative") } IF(num = 0) { DISPLAY("zero") } Which of the following code segments is equivalent to the code segment above?

• IF(num < 0) { DISPLAY("negative") } ELSE { DISPLAY("positive") } IF(num = 0) { DISPLAY("zero") }

• IF(num < 0) { DISPLAY("negative") } ELSE { IF(num = 0) { DISPLAY("zero") } ELSE { DISPLAY("positive") } }

• IF(num ≤ 0) { DISPLAY("negative") } ELSE { IF(num = 0) { DISPLAY("zero") } ELSE { DISPLAY("positive") } }

• IF(num ≤ 0) { DISPLAY("negative") } IF(num = 0) { DISPLAY("zero") } ELSE { DISPLAY("positive") }

• 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

Consider the following program. The variable x is set to 2, then a loop that repeats 4 times updates x using x ← x * 3. Which of the following expressions represents the value stored in the variable x as a result of executing the program?

A student is creating a procedure to determine whether the weather for a particular month was considered very hot. The procedure takes as input a list containing daily high temperatures for a particular month and is intended to return true if the daily high temperature was at least 90 degrees for a majority of days in the month and return false otherwise. PROCEDURE IsHot (temperatureList) { total <- 0 counter <- 0 FOR EACH temperature IN temperatureList { IF (temperature >= 90) { counter <- counter + 1 } total <- total + 1 } RETURN () } Which of the following can be used to replace so that the procedure works as intended?

• counter < 0.5 * total

• counter > 0.5 * total

• total < 0.5 * counter

• total > 0.5 * counter

Programs I and II below are each intended to calculate the sum of the integers from 1 to n. Assume that n is a positive integer (e.g., 1, 2, 3, ...). Which of the following best describes the behavior of the two programs?

• Program I displays the correct sum, but program II does not.

• Program II displays the correct sum, but program I does not.

• Both program I and program II display the correct sum.

• Neither program I nor program II displays the correct sum.

Consider the two programs below. Program A: i ← 1; REPEAT UNTIL (i > 10): DISPLAY i; i ← i + 1. Program B: i ← 1; REPEAT UNTIL (i > 10): i ← i + 1; DISPLAY i. Which of the following best compares the values displayed by programs A and B?

• Program A and program B display identical values.

• Program A and program B display the same values in different orders.

• Program A and program B display the same number of values, but the values differ.

• Program A and program B display a different number of values.

Directions: The question or incomplete statement below is followed by four suggested answers or completions. Select the one that is best in each case. Consider the code segment below. Line 1: IF (a = 0) Line 2: { Line 3: b ← a + 10 Line 4: } Line 5: ELSE Line 6: { Line 7: b ← a + 20 Line 8: } Which of the following changes will NOT affect the results when the code segment is executed?

• Changing line 3 to b ← 10

• Changing line 3 to a ← b + 10

• Changing line 7 to b ← 20

• Changing line 7 to a ← b + 20

The two code segments are each intended to display the average of the numbers in the list numList. Assume that numList contains more than one value. Which of the following best describes the two code segments?

• Code segment I displays the correct average, but code segment II does not.

• Code segment II displays the correct average, but code segment I does not.

• Both code segments display the correct average, but code segment I requires more arithmetic operations than code segment II.

• Both code segments display the correct average, but code segment II requires more arithmetic operations than code segment I.