Question 1

An algorithm that cuts the work in half in each step is an ____ algorithm.

Accepted Answer

A)  O(n) 
B)  O(n2) 
C)  O(log (n)) 
D)  O(n log (n)) 
A)  O(n) 
B)  O(n2) 
C)  O(log (n)) 
D)  O(n log (n))

Question 2

The binarySearch method of the Collections class returns a value in the form of -k - 1 when the target item you are searching for was not found in the array. What does k represent?

Accepted Answer

A)  It is the position of an existing item, and indicates that your target item should come after this existing item. 
B)  It is the position of an existing item, and indicates that your target item should come before this existing item. 
C)  It represents the number of times the array was accessed by the binarySearch method, and can be used for analyzing performance. 
D)  Nothing - it is an arbitrary value. 
A)  It is the position of an existing item, and indicates that your target item should come after this existing item. 
B)  It is the position of an existing item, and indicates that your target item should come before this existing item. 
C)  It represents the number of times the array was accessed by the binarySearch method, and can be used for analyzing performance. 
D)  Nothing - it is an arbitrary value.

Question 3

Suppose a developer gets class XYZ files and documentation from a subcontractor. This class does not implement the Comparable interface. What must be true in order for the developer to sort an array of XYZ objects without modifying the xyz class?

Accepted Answer

A) The XYZ class must implement the Sortable interface. B) XYZ objects must be randomly distributed. C) XYZ objects must be ordered. D) The developer must supply a comparator object belonging to a class that implements the Comparator interface. A) The XYZ class must implement the Sortable interface. B) XYZ objects must be randomly distributed. C) XYZ objects must be ordered. D) The developer must supply a comparator object belonging to a class that implements the Comparator interface.

Question 4

Which of the sorts in the textbook are based on the strategy of divide and conquer?
I quicksort
II mergesort
III insertion sort

Accepted Answer

A)  I 
B)  II 
C)  III 
D)  I and II 
A)  I 
B)  II 
C)  III 
D)  I and II

Question 5

Selection sort has O(n2) complexity. If a computer can sort 1,000 elements in 4 seconds, approximately how many seconds will it take the computer to sort 1,000 times that many, or 1,000,000 elements?

Accepted Answer

A)  16 
B)  1,000 
C)  1,000,000 
D)  4,000,000 
A)  16 
B)  1,000 
C)  1,000,000 
D)  4,000,000

Question 6

In each iteration, selection sort places which element in the correct location?

Accepted Answer

A)  The smallest in the array. 
B)  The smallest element not yet placed in prior iterations. 
C)  The largest element in the array. 
D)  A random element. 
A)  The smallest in the array. 
B)  The smallest element not yet placed in prior iterations. 
C)  The largest element in the array. 
D)  A random element.

Question 7

A binary search is generally ____ a linear search.

Accepted Answer

A)  slower than 
B)  equal to 
C)  less efficient than 
D)  faster than 
A)  slower than 
B)  equal to 
C)  less efficient than 
D)  faster than

Question 8

Suppose the call obj1.compareTo(obj2) returns 0. What can definitely be concluded from the return value?
I obj1 and obj2 are the same object
II obj1 and obj2 objects cannot be compared
III the properties of obj1 and obj2 that are being compared have identical values

Accepted Answer

A)  I 
B)  II 
C)  I and III 
D)  III 
A)  I 
B)  II 
C)  I and III 
D)  III

Question 9

Suppose you wish to sort an array list of objects, but the object class does not implement the Comparable interface. Because you are not allowed to modify this class, you decide to provide a comparator object that implements the Comparator interface. Which method must you implement from this interface to achieve your objective?

Accepted Answer

A)  the sort method. 
B)  the compare method. 
C)  the compareTo method. 
D)  the compareObject method. 
A)  the sort method. 
B)  the compare method. 
C)  the compareTo method. 
D)  the compareObject method.

Question 10

In the textbook, we found that the number of element visits for merge sort totaled n + 5n log2 n. Which of the following is the appropriate big-Oh notation for merge sort?

Accepted Answer

A)  5n log2 n 
B)  n + log2 n 
C)  n + 5n 
D)  n log2 n 
A)  5n log2 n 
B)  n + log2 n 
C)  n + 5n 
D)  n log2 n

Question 11

How many times can an array with 729 elements be cut into three equal pieces?

Accepted Answer

A)  4 
B)  5 
C)  6 
D)  7 
A)  4 
B)  5 
C)  6 
D)  7

Question 12

Consider the sort method shown below for selection sort: public static void sort(int[]A) An exception would occur.

Accepted Answer

A)  {
For (int i = 0; i < a.length - 1; i++)
{
Int minPos = minimumPosition(i);
Swap(minPos, i);
}
}
Suppose we modify the loop condition to read i < a.length. What would be the result? 
B)  The sort would work, but run one more iteration. 
C)  The sort would work but with one less iteration. 
D)  The sort would work exactly the same as before the code modification. 
A)  {
For (int i = 0; i < a.length - 1; i++)
{
Int minPos = minimumPosition(i);
Swap(minPos, i);
}
}
Suppose we modify the loop condition to read i < a.length. What would be the result? 
B)  The sort would work, but run one more iteration. 
C)  The sort would work but with one less iteration. 
D)  The sort would work exactly the same as before the code modification.

Question 13

If you implement a recursive linear search, its performance will be ____.

Accepted Answer

A)  O(n) 
B)  O(n2) 
C)  O(log (n)) 
D)  O(n log (n)) 
A)  O(n) 
B)  O(n2) 
C)  O(log (n)) 
D)  O(n log (n))

Question 14

Given the following code snippet for searching an array:
Int[] arr = {3, 8, 12, 14, 17};
Int newVal = 15;
Int pos = Arrays.binarySearch(arr, newVal);
What value will pos have when this code is executed?

Accepted Answer

A)  5 
B)  -5 
C)  6 
D)  -6 
A)  5 
B)  -5 
C)  6 
D)  -6

Question 15

The code segment below prints some of the elements in an array with size n. Select an expression to complete the code segment so that the resulting algorithm has O(log n) running time. for __________________________
{
System.out.println(array[j]);
}

Accepted Answer

A)  (int j = 0; j < array.length; j = j + 2) 
B)  (int j = 1; j < array.length; j = j * 2) 
C)  (int j = 0; j < array.length / 2; j++) 
D)  (int j = 0; j < array.length; j++) 
A)  (int j = 0; j < array.length; j = j + 2) 
B)  (int j = 1; j < array.length; j = j * 2) 
C)  (int j = 0; j < array.length / 2; j++) 
D)  (int j = 0; j < array.length; j++)

Question 16

How many comparisons does selection sort make when sorting an array of length n?

Accepted Answer

A)  n 
B)  log(2n) 
C)  n( n + 1) / 2 
D)  n. 
A)  n 
B)  log(2n) 
C)  n( n + 1) / 2 
D)  n.

Question 17

If an element is present in an array of length n, how many element visits, on average, are necessary to find it using a linear search?

Accepted Answer

A)  n / 2 
B)  n 
C)  2n 
D)  n2 
A)  n / 2 
B)  n 
C)  2n 
D)  n2

Question 18

Suppose an algorithm requires a total of 3n3 + 2n2 - 3n + 4 visits. In big-Oh notation, the total number of visits is of what order?

Accepted Answer

A)  n2 * n2 
B)  n2 
C)  n6 
D)  n3 
A)  n2 * n2 
B)  n2 
C)  n6 
D)  n3

Question 19

The code segment below is designed to add the elements in an array of integers. Select the expression needed to complete the code segment so that it calculates the running time elapsed. long start = System.currentTimeMillis();
Int sum = 0;
For (int k = 0; k < values.length; k++)
{
Sum = sum + values[k];
}
Long runningTime = ____________________________;

Accepted Answer

A)  System.currentTimeMillis() 
B)  System.currentTimeMillis() - start 
C)  System.currentTimeMillis() + start 
D)  runningTime + start - System.currentTimeMillis() 
A)  System.currentTimeMillis() 
B)  System.currentTimeMillis() - start 
C)  System.currentTimeMillis() + start 
D)  runningTime + start - System.currentTimeMillis()

Question 20

Which of the following arrays can be used in a call to the Arrays.sort method?
I Any array with primitive numeric data, such as int, double, …
II Arrays of String or numeric wrapper classes like, Integer, Double, …
III Any class that implements the Comparable interface

Accepted Answer

A)  I 
B)  II 
C)  I and II 
D)  I, II and III 
A)  I 
B)  II 
C)  I and II 
D)  I, II and III

Exam 14: Sorting and Searching

An algorithm that cuts the work in half in each step is an ____ algorithm.

The binarySearch method of the Collections class returns a value in the form of -k - 1 when the target item you are searching for was not found in the array. What does k represent?

Suppose a developer gets class XYZ files and documentation from a subcontractor. This class does not implement the Comparable interface. What must be true in order for the developer to sort an array of XYZ objects without modifying the xyz class?

Which of the sorts in the textbook are based on the strategy of divide and conquer? I quicksort II mergesort III insertion sort

Selection sort has O(n2) complexity. If a computer can sort 1,000 elements in 4 seconds, approximately how many seconds will it take the computer to sort 1,000 times that many, or 1,000,000 elements?

In each iteration, selection sort places which element in the correct location?

A binary search is generally ____ a linear search.

Suppose the call obj1.compareTo(obj2) returns 0. What can definitely be concluded from the return value? I obj1 and obj2 are the same object II obj1 and obj2 objects cannot be compared III the properties of obj1 and obj2 that are being compared have identical values

In the textbook, we found that the number of element visits for merge sort totaled n + 5n log2 n. Which of the following is the appropriate big-Oh notation for merge sort?

How many times can an array with 729 elements be cut into three equal pieces?

Consider the sort method shown below for selection sort: public static void sort(int[]A) An exception would occur.

If you implement a recursive linear search, its performance will be ____.

Given the following code snippet for searching an array: Int[] arr = {3, 8, 12, 14, 17}; Int newVal = 15; Int pos = Arrays.binarySearch(arr, newVal); What value will pos have when this code is executed?

The code segment below prints some of the elements in an array with size n. Select an expression to complete the code segment so that the resulting algorithm has O(log n) running time. for __________________________ { System.out.println(array[j]); }

How many comparisons does selection sort make when sorting an array of length n?

If an element is present in an array of length n, how many element visits, on average, are necessary to find it using a linear search?

Suppose an algorithm requires a total of 3n3 + 2n2 - 3n + 4 visits. In big-Oh notation, the total number of visits is of what order?

Which of the following arrays can be used in a call to the Arrays.sort method? I Any array with primitive numeric data, such as int, double, … II Arrays of String or numeric wrapper classes like, Integer, Double, … III Any class that implements the Comparable interface

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Selection sort has O(n²) complexity. If a computer can sort 1,000 elements in 4 seconds, approximately how many seconds will it take the computer to sort 1,000 times that many, or 1,000,000 elements?

In the textbook, we found that the number of element visits for merge sort totaled n + 5n log₂n. Which of the following is the appropriate big-Oh notation for merge sort?

Suppose an algorithm requires a total of 3n³ + 2n² - 3n + 4 visits. In big-Oh notation, the total number of visits is of what order?