Deck 13: Recursion

Question 1

Consider the following recursive code snippet:
A.1
B.11
C.5
D.6

Answer 1

5

Question 2

Consider the getArea method from the textbook shown below. What will be the result?
A.The method will return incorrect results for triangles with width equal to 0.
B.The method will return incorrect results for triangles with width equal to 1.
C.The method will return area to be one too high for all triangles.
D.The method will still return correct results for all non-negative width triangles.

Answer 2

The method will still return correct results for all non-negative width triangles.

Question 3

What is required to make a recursive method successful?
I special cases that handle the simplest computations directly
II a recursive call to simplify the computation
III a mutual recursion
A.I, II, and III
B.II only
C.I only
D.I and II only

Answer 3

I and II only

Question 4

Consider the recursive method myPrint shown in this code snippet: What does this method do?
A.Prints a positive int value forward, digit by digit.
B.Divides the int by 10 and prints out the result.
C.Divides the int by 10 and prints out its last digit.
D.Prints a positive int value backward, digit by digit.

Question 5

Consider the following code snippet for recursive addition: Identify the terminating condition in this recursive method.
A.there is no terminating condition
B.i == 0
C.return j
D.return add(i - 1, j + 1)

Question 6

Consider the code for the recursive method riddle shown in this code snippet: To avoid infinite recursion, which of the following lines of code should replace the current terminating case?
A.if (n <= 0)
B.if (n == -1)
C.if (n >= 0)
D.The terminating case as shown will avoid infinite recursion.

Question 7

Insert the missing code in the following code fragment.This fragment is intended to recursively compute xn, where x and n are both non-negative integers:
A.return power(x, n - 1);
B.return x;
C.return 1;
D.return x * power(x, n - 1);

Question 8

Consider the getArea method from the textbook shown below. Where is/are the recursive call(s)?
A.lines #1 and #2
B.line #4
C.line #1
D.line #2

Question 9

Consider the getArea method from the book shown below. What will happen when this code is executed?
A.Nothing - the method would still be correct.
B.We would lose our only recursive case.
C.A positive width would reduce the correct area by 1.
D.A negative or zero width would cause problems.

Question 10

Consider the following code snippet for calculating Fibonacci numbers recursively: Identify the terminating condition in this recursive method.
A.n < 1
B.n <= 1
C.fib(n - 1)
D.fib(n - 1) + fib(n - 1)

Question 11

A recursive method without a special terminating case would _________
A.be more efficient.
B.never terminate.
C.end immediately.
D.not be recursive.

Question 12

Consider the following recursive code snippet: }
Identify the terminating condition(s) of method mystery?
A.n <= 0
B.n > 0
C.n == 1
D.n <= 0 or n == 1

Question 13

Complete the code for the recursive method printSum shown in this code snippet, which is intended to return the sum of digits from 1 to n:
A.return (n + printSum(n - 1));
B.return (n - printSum(n - 1));
C.return (n + printSum(n + 1));
D.return (printSum(n - 1));

Question 14

If recursion does not have a special terminating case, what error will occur?
A.Illegal argument
B.Out of memory
C.Stack overflow
D.Index out of range

Question 15

Consider the getArea method from the textbook shown below:
A.Those with width equal to 0.
B.Triangles of any width.
C.Those with width equal to 1.
D.Those with width greater than or equal to 2.

Question 16

Consider the recursive method myPrint: What is printed for the call myPrint(8)?
A.4
B.21
C.10
D.8

Question 17

Consider the following recursive code snippet: What value is returned from a call to mystery(3,6)?
A.18
B.3
C.6
D.729

Question 18

Consider the code for the recursive method mystery shown in this code snippet: What will be printed by the statement System.out.println(mystery(-4));?
A.Nothing - a StackoverflowError exception will occur
B.0
C.-22
D.-10

Question 19

Consider the getArea method from the textbook shown below. Where is/are the terminating condition(s)?
A.line #2
B.line #4
C.line #1
D.lines #1 and #2

Question 20

Consider the recursive method myPrint in this code snippet: What is printed for the call myPrint(821)?
A.821
B.12
C.10
D.128

Question 21

Would switching the special case order affect the return value of the following method?
A.An exception will be thrown.
B.Yes
C.No
D.It is impossible to tell.

Question 22

Consider the problem of arranging matchsticks so as to form a row of squares, as shown below for three squares and ten matchsticks.
A.4 * squares;
B.3 + matchsticks(squares - 1);
C.4 + matchsticks(squares - 1);
D.matchsticks(squares + 4);

Question 23

Consider the method below, which implements the exponentiation operation recursively.Select the statement that should be used to complete the method so that it handles the special case correctly.
A.return 0;
B.return 1 * power(base, exponent - 1);
C.return base;
D.return 1;

Question 24

Consider the method below, which displays the characters from a String in reverse order.Each character appears on a separate line.Select the statement that should be used to complete the method so that it performs a recursive method call correctly.
A.printReverse(word.length() - 1);
B.printReverse(word.substring(1));
C.printReverse(word);
D.printReverse(new String(word.charAt(1)));

Question 25

Consider the method powerOfTwo shown below: What is the best interpretation of line #1?
A.1 is an invalid choice for n
B.Any multiple of one is a power of two
C.One is not a power of two
D.One is a power of two

Question 26

Which of the following options could be used as a terminating condition for a recursive method that finds the middle character of a String with any number of characters?
I the length of the String is 1
II first and last String characters match
III the String is not empty
A.I only
B.I and III only
C.I, II and III
D.II only

Question 27

If a recursive method does not simplify the computation within the method and the base case is not called, what will be the result?
A.The recursion calculation will occur correctly regardless.
B.Infinite recursion will occur.
C.This cannot be determined.
D.The terminating condition will be executed and recursion will end.

Question 28

Consider the method powerOfTwo shown below: How many recursive calls are made from the original call powerOfTwo(63) (not including the original call)?
A.1
B.6
C.0
D.4

Question 29

Complete the code for the recursive method shown below, which is intended to compute the sum of the first n positive integers:
A.return n + s(n - 1);
B.return s(n) + n - 1;
C.return n + (n - 1);
D.return n + s(n + 1);

Question 30

Consider the getArea method from the textbook shown below: This would cause infinite recursion for ____.
A.triangles with width equal to 1
B.triangles with width equal to 0
C.triangles with width greater than or equal to 2
D.triangles of any width

Question 31

Complete the code for the myFactorial recursive method shown below, which is intended to compute the factorial of the value passed to the method:
A.return (anInteger * (myFactorial(anInteger - 1)));
B.return (anInteger * (myFactorial(anInteger)));
C.return ((anInteger - 1) * (myFactorial(anInteger)));
D.return ((anInteger - 1)*(myFactorial(anInteger - 1)));

Question 32

____ recursion can occur when a recursive algorithm does not contain a special case to handle the simplest computations directly.
A.Non-mutual
B.Terminating condition
C.Mutual
D.Infinite

Question 33

Consider the following recursive code snippet: What parameter values for n would cause an infinite recursion problem in the following method?
A.all n with n < 0
B.n == 0
C.all n with n >= 0
D.n == 1

Question 34

Complete the code for the myFactorial recursive method shown below, which is intended to compute the factorial of the value passed to the method:
A.return 0;
B.return myFactorial(anInteger);
C.return 1;
D.return -anInteger;

Question 35

Complete the code for the myFactorial recursive method shown below, which is intended to compute the factorial of the value passed to the method:
A.if (anInteger * (anInteger - 1) == 1)
B.if (anInteger == 1)
C.if (myFactorial(anInteger) == 1)
D.if ((anInteger - 1) == 1)

Question 36

How many recursive calls to the fib method shown below would be made from an original call to fib(4)? (Do not count the original call)
A.8
B.4
C.1
D.2

Question 37

Consider the method below, which prints the digits of an arbitrary positive integer in reverse order, one digit per line.The method should print the last digit first.Then, it should recursively print the integer obtained by removing the last digit.Select the statements that should be used to complete the method.

Question 38

Consider the method powerOfTwo shown below: How many recursive calls are made from the original call of powerOfTwo(64) (not including the original call)?
A.6
B.4
C.8
D.2

Question 39

Consider the getArea method from the textbook shown below: If line #1 was eliminated from the method, what would be the result when calling getArea?
A.A positive width would reduce the correct area by 1.
B.We would lose our only recursive case.
C.Nothing - the method would still work correctly.
D.A negative or zero width would cause problems.

Question 40

When a recursive method is called correctly, and it does not perform recursion, what must be true?
A.Both a terminating condition and a recursive case condition were true.
B.A terminating condition was true.
C.All recursive case conditions were true.
D.One recursive case condition was true.

Question 41

Given the following code snippet: What value will be returned when this code is executed with a call to newCalc(15)?
A.2.5
B.5
C.5.5
D.2

Question 42

Given the following class code: What values will be printed when this code is executed?
A.3, 6, and 9
B.6
C.1, 3, 6, and 9
D.9

Question 43

Given the following code snippet: What value will be returned when this code is executed with a call to newCalc(15)?
A.2
B.6.5
C.2.5
D.6

Question 44

Consider the code for the recursive method printSum shown in this code snippet, which is intended to return the sum of digits from 1 to n: Which of the following statements is correct?
A.line #3 is incorrect, and should be changed to return (n + printSum(n + 1));
B.line #1 is incorrect, and should be changed to if (n <= 1)
C.line #3 is incorrect, and should be changed to return (n + printSum(n - 1));
D.line #3 is incorrect, and should be changed to return (printSum(n - 1));

Question 45

Complete the following code snippet, which is intended to be a recursive method that will find the smallest value in an array of double values from index to the end of the array:
A.return elements[index];
B.return 0;
C.return 1;
D.return elements[0];

Question 46

Given the following class code: What values will be printed when this code is executed?
A.4
B.8
C.0, 4, and 8
D.4 and 8

Question 47

Complete the following code snippet, which is intended to be a recursive method that will find the sum of all elements in an array of double values from the beginning of the array to index:
A.return (arr[index] + findSum(arr, index + 1));
B.return (findSum(arr, index - 1));
C.return (findSum(arr, index + 1));
D.return (arr[index] + findSum(arr, index - 1));

Question 48

Given the following class code: What values will be printed?
A.1, 3, and 6
B.3, 6, 9, and 12
C.1, 3, 6, and 9
D.3, 6, and 9

Question 49

Given the following code snippet: What value will be returned when this code is executed with a call to newCalc(5)?
A.5
B.1.5
C.5.5
D.1

Question 50

The method below generates all nonempty substrings of a word passed as argument.Assuming that the string contains no duplicate characters, select the statement to complete the method so that it prints all nonempty substrings correctly.
A.printSubstrings(word.substring(0));
B.printSubstrings(word.substring(1));
C.printSubstrings(word.substring(word.length()));
D.printSubstrings(word.substring(word.length() - 1));

Question 51

Given the following code snippet: What value will be returned when this code is executed with a call to newCalc(5)?
A.2.5
B.5.5
C.5
D.2

Question 52

Complete the following code snippet, which is intended to be a recursive method that reverses a String value:
A.return reverseIt;
B.return reverseIt;
C.return reverseIt;
D.return reverseIt;

Question 53

Complete the code for the calcPower recursive method shown below, which is intended to raise the base number passed into the method to the exponent power passed into the method:
A.answer = 0;
B.answer = 1;
C.answer = calcPower(1);
D.answer = -1;

Question 54

Complete the following code snippet, which is intended to be a recursive method that will find the smallest value in an array of double values from index to the end of the array:
A.minVal(elements, index - 1)
B.minVal(index - 1)
C.minVal(elements, index + 1)
D.minVal(index + 1)

Question 55

Complete the following code snippet, which is intended to be a recursive method that reverses a String value:
A.return s.charAt(0);
B.return 0;
C.return s.substring(1);
D.return s;

Question 56

Given the following class code: What values will be printed when this code is executed?
A.8
B.4
C.4 and 8
D.0, 4, and 8

Question 57

Which of the following is NOT true about debugging a recursive method by setting a breakpoint on the line containing a return statement?
A.You cannot debug a recursive method with the debugger.
B.The debugger's call stack will show all the calls to the recursive method that are pending.
C.You can select a pending call and then inspect the value of its variables.
D.The last call on the stack represents the first recursive call to reach the return statement.

Question 58

Complete the code for the calcPower recursive method shown below, which is intended to raise the base number passed into the method to the exponent power passed into the method:
A.answer = baseNum * calcPower (baseNum -1, exponent - 1);
B.answer = baseNum * calcPower (baseNum, exponent);
C.answer = baseNum * calcPower (baseNum -1, exponent);
D.answer = baseNum * calcPower (baseNum, exponent - 1);

Question 59

Complete the following code snippet, which is intended to be a recursive method that will find the sum of all elements in an array of double values from the beginning of the array to index:
A.return arr[index + 1];
B.return arr[1];
C.return arr[index - 1];
D.return arr[index];

Question 60

Complete the code for the calcPower recursive method shown below, which is intended to raise the base number passed into the method to the exponent power passed into the method:
A.if (exponent == -1)
B.if (exponent == 1)
C.if (exponent != 1)
D.if (exponent == 0)

Question 61

Consider the code for the myFactorial recursive method shown below, which is intended to compute the factorial of the value passed to the method: If you set a breakpoint on line #2 and then call myFactorial(4), how many calls to myFactorial will be visible on the debugger's call stack when the program suspends for the breakpoint?
A.0 because the answer was returned
B.3
C.4
D.1

Question 62

Consider the fib method from the textbook shown below: Computing the 7th fibonacci number, fib(7), recursively computes fib(6), fib(5), and fib(4) ___ times respectively.
A.6, 5, and 4
B.3, 2, and 1
C.1, 2, and 3
D.4, 5, and 6

Question 63

A palindrome is a word or phrase that reads the same forward or backward.Consider the following code snippet: What is the purpose of the palindrome method?
A.Recursively call itself.
B.Provide the string, along with its first and last indexes to the recursive isPal method.
C.Send the recursive isPal method its terminating condition.
D.Return the palindrome to the calling method.

Question 64

Consider the square method shown below that takes a non-negative int argument.Complete the code for the square method so that it correctly calls the squareHelper method to produce the square of n.
A.return squareHelper(n - 1, n)
B.return squareHelper(n, n - 1)
C.return square(n)
D.return squareHelper(n, n)

Question 65

Consider the recursive version of the fib method from the textbook shown below: How many recursive calls to fib(2) will be made from the original call of fib(6)?
A.4
B.3
C.5
D.2

Question 66

Consider the recursive version of the fib method from the textbook shown below: How many total recursive calls (not counting the original call) to fib will be made from the original call of fib(7)?
A.12
B.32
C.24
D.30

Question 67

Consider the square method shown below that takes a non-negative int argument: What would a call to square(7) return?
A.7
B.14
C.13
D.49

Question 68

Consider the square method shown below that takes a non-negative int argument. What would a call to square(4) return?
A.256
B.4
C.16
D.64

Question 69

A palindrome is a word or phrase that reads the same forward or backward.Consider the following code snippet:
A.You have reached the middle of the string.
B.It cannot be determined if the string is a palindrome.
C.An empty or one-character string is considered a palindrome.
D.The string is not a palindrome.

Question 70

Assume that recursive method search returns true if argument value is one of the elements in the section of the array limited by the firstIndex and lastIndex arguments.What statement can be used in main to determine if the value 7 is one of the elements in array values?
A.search(7, values, 1, values.length)
B.search(7, values, 1, values.length - 1)
C.search(7, values, 0, values.length)
D.search(7, values, 0, values.length - 1)

Question 71

A palindrome is a word or phrase that reads the same forward or backward.Consider the methods palindrome and isPal shown below: The method isPal as shown here would be considered to be a ____ method.
A.terminating
B.static
C.recursive helper
D.public

Question 72

Consider the iterative version of the fib method from the textbook shown below: How many iterations of the for loop will there be for the call fib(6)?
A.3
B.5
C.6
D.4

Question 73

Consider the recursive version of the fib method from the textbook shown below: How many total recursive calls (not counting the original call) to fib will be made from the original call of fib(6)?
A.14
B.12
C.6
D.20

Question 74

Why does the best recursive method usually run slightly slower than its iterative counterpart?
A.Each recursive method call takes processor time.
B.Multiple recursive cases must be considered.
C.Checking multiple terminating conditions take more processor time.
D.Testing the terminating condition takes longer.

Question 75

Consider the problem of displaying a pattern of asterisks that form a triangle of height h, as shown below for h = 4:
A.shape(0, height - 1);
B.shape(0, height - 1);
C.shape(1, height);
D.shape(0, height);

Question 76

Consider the helper method reversePrint, which uses recursion to display in reverse the elements in a section of an array limited by the firstIndex and lastIndex arguments.What statement should be used to complete the recursive method?
A.reversePrint(array, firstIndex, lastIndex - 1);
B.reversePrint(array, firstIndex + 1, lastIndex);
C.reversePrint(array, firstIndex + 1, lastIndex - 1);
D.reversePrint(array, firstIndex, lastIndex + 1);

Question 77

Consider the recursive version of the fib method from the textbook shown below: How many more recursive calls to fib will be made from the original call of fib(7) than from the original call of fib(6) (not counting the original calls)?
A.2
B.10
C.5
D.1

Question 78

Consider the helper method reversePrint, which uses recursion to display in reverse the elements in a section of an array limited by the firstIndex and lastIndex arguments.What statement should be used to complete the recursive method?
A.array[firstIndex]
B.array[firstIndex+1]
C.array[lastIndex-1]
D.array[lastIndex]

Question 79

A palindrome is a word or phrase spelled which reads the same forward or backward.Consider the following code snippet: What does the method palindrome return?
A.false
B.a palindrome not found exception
C.the Boolean value returned from the isPal method
D.true

Question 80

Consider the fib method from the textbook shown below. Calling fib(3) will trigger ___ recursive call(s) and execute the terminating condition ___ time(s), respectively.
A.1, 1
B.1, 2
C.2, 2
D.2, 1