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12.9. Easy Multiple Choice Questions

These problems are easier than most of those that you will usually see on the AP CS A exam.

12-7-1: Which line has the recursive call?

public static int factorial(int n)
{
   if (n == 0)
      return 1;
   else return n * factorial(n-1);
}

• 1
• This is the method declaration. Look for a call to the same method in the body of the method.
• 3
• This is a conditional, not a method call.
• 4
• This is a return statement, not a method call.
• 5
• This line contains a call to the same method which makes this method recursive.

12-7-2: Which line has the recursive call?

public String starString(int n)
{
   if (n == 0) {
      return "*";
   } else {
      return starString(n - 1) + starString(n - 1);
   }
}

• 1
• This is the method declaration. Look for a call to the same method in the body of the method.
• 3
• This is a conditional, not a method call.
• 4
• This is a return statement, not a method call.
• 5
• This is an else which is part of a conditional, not a method call.
• 6
• This line contains a call to the same method which makes this method recursive.

12-7-3: How many recursive calls does the following method contain?

public static int fibonacci(int n)
{
   if (n == 0)
      return 0;
   else if (n == 1)
      return 1;
   else return fibonacci(n-1) + fibonacci(n-2);
    }

• 0
• Look at line 7 more closely.
• 1
• Many recursive methods only have one recursive call. But, this one has two.
• 2
• Line 7 has two calls to fibonacci.
• 3
• There are not 3 calls to fibonacci.

12-7-4: How many recursive calls does the following method contain?

public static int multiplyEvens(int n)
{
   if (n == 1) {
      return 2;
   } else {
      return 2 * n * multiplyEvens(n - 1);
   }
}

• 0
• Look for a call to the same method in the body of the method.
• 1
• Line 6 has one call to multiplyEvens.
• 2
• Where do you see 2 calls to multiplyEvens?
• 3
• Where do you see 3 calls to multiplyEvens?

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