AP CSA Recursion (10.1)

Which of the following best describes the output produced by the method call mystery(val)?

• All integers from 1 to val, separated by spaces

• All integers from val to 1, separated by spaces

• The digits of val in their original order, separated by spaces

• The digits of val in reverse order, separated by spaces

• The last digit of val, then a space, then the first digit of val

Consider the following method, which is intended to return the sum of all the even digits in its parameter num. For example, sumEvens(15555234) should return 6, the sum of 2 and 4.

Which of the following can be used as a replacement for /* missing statement */ so that the sumEvens method works as intended?

• return sumEvens(num % 10);

• return sumEvens(num / 10);

• return num % 10 + sumEvens(num % 10);

• return num % 10 + sumEvens(num / 10);

• return num / 10 + sumEvens(num % 10);

Which of the following best describes the result of the call doSomething(myString)?

• The method call returns a String containing the contents of myString unchanged.

• The method call returns a String containing the contents of myString with the order of the characters reversed from their order in myString.

• The method call returns a String containing all but the first character of myString.

• The method call returns a String containing only the first and second characters of myString.

• The method call returns a String containing only the first and last characters of myString.

Which of the following best describes the value returned by the method call calc(num)?

• The int value 9

• The leftmost digit of num

• The rightmost digit of num

• The number of digits in num

• The result of the integer division of num by 10

Consider the following recursive method, which is intended to return a String with any consecutive duplicate characters removed. For example, removeDupChars("aabcccd") returns "abcd".

Which of the following can replace /* missing code */ so that removeDupChars works as intended?

• return removeDupChars(str.substring(2));

• return removeDupChars(str.substring(1)) + str.substring(0, 1);

• return removeDupChars(str.substring(2)) + str.substring(1, 2);

• return str.substring(0, 1) + removeDupChars(str.substring(1));

• return str.substring(1, 2) + removeDupChars(str.substring(2));

Consider the following recursive method, which is intended to display the binary equivalent of a decimal number. For example, toBinary(100) should display 1100100.

Which of the following can replace /* missing code */ so that toBinary works as intended?

• System.out.print(num % 2);

  toBinary(num / 2);

• System.out.print(num / 2);

  toBinary(num % 2);

• toBinary(num % 2);

  System.out.print(num / 2);

• toBinary(num / 2);

  System.out.print(num % 2);

• toBinary(num / 2);

  System.out.print(num / 2);