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13.8. Easy Multiple Choice Questions

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

13-8-1: What would the following code return from mystery([90, -30, 50], 50)?

 public static int mystery(int[] elements, int target)
 {
   for (int j = 0; j < elements.length; j++)
   {
      if (elements[j] == target)
      {
         return j;
      }
  }
  return -1;
}

• -1
• This value is returned if the target is not in the list since this is a sequential search.
• 0
• This would be true if the target was 90 since this is a sequential search.
• 1
• This would be true if the target was -30 since this is a sequential search.
• 2
• This is a sequential search that returns the index where the target appears in the elements list
• 50
• A sequential search returns the index, not the value. What is the index of the 50?

You can step through the code above by clicking on the following Ex-12-7-1.

13-8-2: What would the following code return from mystery([90, -30, 50], -20)?

 public static int mystery(int[] elements, int target)
 {
   for (int j = 0; j < elements.length; j++)
   {
      if (elements[j] == target)
      {
         return j;
      }
  }
  return -1;
}

• -1
• A sequential search returns -1 if the target value is not found in the list.
• 0
• This would be true if the target was 90 since this is a sequential search.
• 1
• This would be true if the target was -30 since this is a sequential search.
• 2
• This would be true if the target was
• -20
• A sequential search returns negative one when the value isn't found in the list.

You can step through the code above by clicking on the following Ex-12-7-2.

13-8-3: Consider the binarySearch method below. How many times would the while loop execute if you first do int[] arr = {2, 10, 23, 31, 55, 86} and then call binarySearch(arr,2)?

public static int binarySearch(int[] elements, int target) {
   int left = 0;
   int right = elements.length - 1;
   while (left <= right)
   {
      int middle = (left + right) / 2;
      if (target < elements[middle])
      {
         right = middle - 1;
      }
      else if (target > elements[middle])
      {
         left = middle + 1;
      }
      else {
         return middle;
      }
    }
    return -1;
}

• 1
• This would be true if we were looking for 23.
• 2
• It first compares 23 at index 2 (5 / 2 is 2) to 2. The second time it compares the 2 at index 0 (1 / 2 = 0) to 2 and returns 0.
• 3
• This would be true if we were looking for 10.

You can step through the code above by clicking on the following Ex-12-7-3.

13-8-4: Which sort contains a recursive call?

• selection sort
• A selection sort has nested for loops.
• insertion sort
• An insertion sort has a while loop inside a for loop.
• merge sort
• A merge sort has a recursive call to mergeSortHelper in mergeSortHelper.

13-8-5: Under what condition will an ascending insertion sort execute the slowest?

• If the data is already sorted in ascending order
• If the data is already sorted in the correct order you don't need to move any values.
• If the data is already sorted in descending order
• All values will have to be moved multiple times since the data was sorted into descending order.
• It will always take the same amount of time to execute
• This would be true if it was a selection sort.

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