AP Computer Science Loops Test

1. A for loop is an example of a pretest loop

True

False

A for loop is an example of a pretest loop because the condition is evaluated before the loop body is executed. In a for loop, the condition is checked initially, and if it is true, the loop body is executed. If the condition is false, the loop is not executed at all. This means that the loop may not run even once if the condition is false from the beginning. Therefore, a for loop falls under the category of pretest loops.

Explanation

A for loop is an example of a pretest loop because the condition is evaluated before the loop body is executed. In a for loop, the condition is checked initially, and if it is true, the loop body is executed. If the condition is false, the loop is not executed at all. This means that the loop may not run even once if the condition is false from the beginning. Therefore, a for loop falls under the category of pretest loops.

2. If x is an int where x = 0, what will x be after the following loop terminates? while (x < 100) { x *= 2; }

2

64

100

128

It's an infinite loop

not-available-via-ai

Explanation

not-available-via-ai

3. If x is an int where x = 1, what will x be after the following loop terminates? while (x < 100) { x *= 2; }

2

64

100

128

It's an infinite loop

The given loop multiplies the value of x by 2 repeatedly until x becomes greater than or equal to 100. Since the initial value of x is 1, it will be multiplied by 2 repeatedly until it reaches 128, which is the largest power of 2 that is less than 100. Therefore, the value of x after the loop terminates will be 128.

Explanation

The given loop multiplies the value of x by 2 repeatedly until x becomes greater than or equal to 100. Since the initial value of x is 1, it will be multiplied by 2 repeatedly until it reaches 128, which is the largest power of 2 that is less than 100. Therefore, the value of x after the loop terminates will be 128.

4. The following nested loop structure will execute the inner most statement (x++) how many times? int j = 0, x = 0; while (j++ < 100) { int k = 100; while (k-- > 0) { x++; } }

100

200

10,000

20,000

100,000

The innermost statement (x++) will execute 10,000 times. This is because the outer while loop will iterate 100 times (j++ 0). Therefore, the innermost statement will execute a total of 10,000 times.

Explanation

The innermost statement (x++) will execute 10,000 times. This is because the outer while loop will iterate 100 times (j++ 0). Therefore, the innermost statement will execute a total of 10,000 times.

5. Consider the following code segment: for (int k = 0; k < 20; k = k + 2) { if (k % 3 != 1) { System.out.print(k + " "); } } What is printed as a result of executing the code segment?

4 16

4 10 16

0 6 12 18

0 2 6 8 12 14 18

0 2 4 6 8 10 12 14 16 18

The code segment uses a for loop to iterate through values of k from 0 to 20 with a step size of 2. Inside the loop, there is an if statement that checks if k modulo 3 is not equal to 1. If this condition is true, the value of k is printed.

Starting from 0, the loop will iterate through the values: 0, 2, 4, 6, 8, 10, 12, 14, 16, 18.

Out of these values, only 0, 2, 6, 8, 12, 14, and 18 satisfy the condition in the if statement. Therefore, these values will be printed.

Hence, the output of the code segment will be: 0 2 6 8 12 14 18.

Explanation

The code segment uses a for loop to iterate through values of k from 0 to 20 with a step size of 2. Inside the loop, there is an if statement that checks if k modulo 3 is not equal to 1. If this condition is true, the value of k is printed.

Starting from 0, the loop will iterate through the values: 0, 2, 4, 6, 8, 10, 12, 14, 16, 18.

Out of these values, only 0, 2, 6, 8, 12, 14, and 18 satisfy the condition in the if statement. Therefore, these values will be printed.

Hence, the output of the code segment will be: 0 2 6 8 12 14 18.

6. Given that s is a String, what does the following loop do? int j = s.length( ); while (j > 0) { System.out.print(s.charAt(j-1)); j -= 1; }

Prints s out backwards

Prints s out forwards

Prints s out backwards, skipping the last character

Prints s out backwards, skipping the first character

It's a run-time error because there is no character at s.charAt(j-1) for j = 0

The given loop iterates through the characters of the string "s" in reverse order. It starts from the last character of the string and prints each character one by one until it reaches the first character. Therefore, the loop prints the string "s" out backwards.

Explanation

The given loop iterates through the characters of the string "s" in reverse order. It starts from the last character of the string and prints each character one by one until it reaches the first character. Therefore, the loop prints the string "s" out backwards.