1. Chapter 14: Searching and Sorting
Java Programming:
From Problem Analysis to Program Design,
Fourth Edition

2. Chapter Objectives
Learn how to implement the sequential search algorithm.
Explore how to sort an array using bubble sort, selection sort, and insertion sort algorithms.
Learn how to implement the binary search algorithm.
Become aware of the class Vector.
Learn more about manipulating strings using the class String.
Java Programming: From Problem Analysis to Program Design, Second Edition

3. List Processing List: A set of values of the same type.
Basic operations performed on a list:
Search list for given item.
Sort list.
Insert item in list.
Delete item from list.
Java Programming: From Problem Analysis to Program Design, Second Edition

4. Search Necessary components to search a list: After search completed:
Array containing the list.
Length of the list.
Item for which you are searching.
After search completed:
If item found, report “success” and return location in array.
If item not found, report “failure.”
Java Programming: From Problem Analysis to Program Design, Second Edition

5. Search public static int seqSearch(int[] list,
int listLength, int searchItem) {
int loc;
boolean found = false;
for (loc = 0; loc < listLength; loc++)
if (list[loc] == searchItem)
found = true;
break; }
if (found)
return loc;
else
return -1;
Java Programming: From Problem Analysis to Program Design, Second Edition

6. Sorting a List Bubble sort
Suppose list[0...n - 1] is a list of n elements, indexed 0 to n - 1. We want to rearrange (sort) the elements of list in increasing order. The bubble sort algorithm works as follows:
In a series of n - 1 iterations, the successive elements, list[index] and list[index + 1], of list are compared. If list[index] is greater than list[index + 1], then the elements list[index] and list[index + 1] are swapped (interchanged).
Java Programming: From Problem Analysis to Program Design, Second Edition

7. Bubble Sort
Java Programming: From Problem Analysis to Program Design, Second Edition

8. Bubble Sort
Java Programming: From Problem Analysis to Program Design, Second Edition

9. Bubble Sort public static void bubbleSort(int list[], int listLength){
int temp;
int counter, index;
for (counter = 0; counter < listLength - 1;
counter++)
for (index = 0;
index < listLength - 1 – counter;
index++)
if (list[index] > list[index + 1])
temp = list[index];
list[index] = list[index + 1];
list[index + 1] = temp; }
Java Programming: From Problem Analysis to Program Design, Second Edition

10. Bubble Sort
For a list of length n, an average bubble sort makes n(n – 1) / 2 key comparisons and about n(n – 1) / 4 item assignments.
Therefore, if n = 1000, bubble sort makes about 500,000 key comparisons and about 250,000 item assignments to sort the list.
Java Programming: From Problem Analysis to Program Design, Second Edition

11. Selection Sort
List is sorted by selecting list element and moving it to its proper position.
Algorithm finds position of smallest element and moves it to top of unsorted portion of list.
Repeats process above until entire list is sorted.
Java Programming: From Problem Analysis to Program Design, Second Edition

12. Selection Sort
Java Programming: From Problem Analysis to Program Design, Second Edition

13. Selection Sort
Java Programming: From Problem Analysis to Program Design, Second Edition

14. Selection Sort public static void selectionSort(int[] list,
int listLength) {
int index;
int smallestIndex;
int minIndex;
int temp;
for (index = 0; index < listLength – 1; index++)
smallestIndex = index;
for (minIndex = index + 1;
minIndex < listLength; minIndex++)
if (list[minIndex] < list[smallestIndex])
smallestIndex = minIndex;
temp = list[smallestIndex];
list[smallestIndex] = list[index];
list[index] = temp; }
Java Programming: From Problem Analysis to Program Design, Second Edition

15. Selection Sort
For a list of length n, an average selection sort makes n(n – 1) / 2 key comparisons and 3(n – 1) item assignments.
Therefore, if n = 1000, selection sort makes about 500,000 key comparisons and about 3000 item assignments to sort the list.
Java Programming: From Problem Analysis to Program Design, Second Edition

16. Insertion Sort
The insertion sort algorithm sorts the list by moving each element to its proper place.
Java Programming: From Problem Analysis to Program Design, Second Edition

17. Insertion Sort
Java Programming: From Problem Analysis to Program Design, Second Edition

18. Insertion Sort
Java Programming: From Problem Analysis to Program Design, Second Edition

19. Insertion Sort
Java Programming: From Problem Analysis to Program Design, Second Edition

20. Insertion Sort public static void insertionSort(int[] list,
int noOfElements) {
int firstOutOfOrder, location;
int temp;
for (firstOutOfOrder = 1;
firstOutOfOrder < noOfElements;
firstOutOfOrder++)
if (list[firstOutOfOrder] < list[firstOutOfOrder - 1])
temp = list[firstOutOfOrder];
location = firstOutOfOrder; do
list[location] = list[location - 1];
location--; }
while(location > 0 && list[location - 1] > temp);
list[location] = temp;
} //end insertionSort
Java Programming: From Problem Analysis to Program Design, Second Edition

21. Insertion Sort
For a list of length n, on average, the insertion sort makes (n2 + 3n – 4) / 4 key comparisons and about n(n – 1) / 4 item assignments.
Therefore, if n = 1000, the insertion sort makes about 250,000 key comparisons and about 250,000 item assignments to sort the list.
Java Programming: From Problem Analysis to Program Design, Second Edition

22. Sequential Ordered Search
public static int seqOrderedSearch(int[] list,
int listLength, int searchItem) {
int loc; //Line 1
boolean found = false; //Line 2
for (loc = 0; loc < listLength; loc++) //Line 3
if (list[loc] >= searchItem) //Line 4
found = true; //Line 5
break; //Line 6 }
if (found) //Line 7
if (list[loc] == searchItem) //Line 8
return loc; //Line 9
else //Line 10
return -1; //Line 11
else //Line 12
return -1; //Line 13
Java Programming: From Problem Analysis to Program Design, Second Edition

23. Binary Search Can only be performed on a sorted list.
Uses divide and conquer technique to search list.
If L is a sorted list of size n, to determine whether an element is in L, the binary search makes at most 2 * log2n + 2 key comparisons.
(Faster than a sequential search.)
Java Programming: From Problem Analysis to Program Design, Second Edition

24. Binary Search Algorithm
Search item is compared with middle element of list.
If search item < middle element of list, search is restricted to first half of the list.
If search item > middle element of list, search is restricted to second half of the list.
If search item = middle element, search is complete.
Java Programming: From Problem Analysis to Program Design, Second Edition

25. Binary Search Algorithm
Determine whether 75 is in the list.
Java Programming: From Problem Analysis to Program Design, Second Edition

26. Binary Search Algorithm
public static int binarySearch(int[] list, int listLength,
int searchItem) {
int first = 0;
int last = listLength - 1;
int mid;
boolean found = false;
while (first <= last && !found)
mid = (first + last) / 2;
if (list[mid] == searchItem)
found = true;
else
if (list[mid] > searchItem)
last = mid - 1;
first = mid + 1; }
if (found)
return mid;
return –1;
} //end binarySearch
Java Programming: From Problem Analysis to Program Design, Second Edition

27. Vectors The class Vector can be used to implement a list.
Unlike an array, the size of a Vector object can grow/shrink during program execution.
You do not need to worry about the number of data elements in a vector.
Java Programming: From Problem Analysis to Program Design, Second Edition

28. Members of the class Vector
Java Programming: From Problem Analysis to Program Design, Second Edition

29. Members of the class Vector
Java Programming: From Problem Analysis to Program Design, Second Edition

30. Members of the class Vector
Java Programming: From Problem Analysis to Program Design, Second Edition

31. Members of the class Vector
Java Programming: From Problem Analysis to Program Design, Second Edition

32. Vectors
Every element of a Vector object is a reference variable of the type Object.
To add an element into a Vector object:
Create appropriate object.
Store data into object.
Store address of object holding data into Vector object element.
Java Programming: From Problem Analysis to Program Design, Second Edition

33. Vectors Vector<String> stringList = new Vector<String>();
stringList.addElement("Spring");
stringList.addElement("Summer");
stringList.addElement("Fall");
stringList.addElement("Winter");
Java Programming: From Problem Analysis to Program Design, Second Edition

34. Programming Example: Election Results
Input: Two files
File 1: Candidates’ names
File 2: Voting data
Voting data format:
candidate_name region# number_of_votes_for_this_candidate
Java Programming: From Problem Analysis to Program Design, Second Edition

35. Programming Example: Election Results
Output: Election results in a tabular form.
Each candidate’s name.
Number of votes each candidate received in each region.
Total number of votes each candidate received.
Java Programming: From Problem Analysis to Program Design, Second Edition

36. Programming Example: Election Results (Solution)
The solution includes:
Reading the candidates’ names into the array candidateName.
A two-dimensional array consisting of the votes by region.
An array consisting of the total votes parallel to the candidateName array.
Java Programming: From Problem Analysis to Program Design, Second Edition

37. Programming Example: Election Results (Solution)
Sorting the array candidatesName.
Processing the voting data.
Calculating the total votes received by each candidate.
Outputting the results in tabular form.
Java Programming: From Problem Analysis to Program Design, Second Edition

38. Programming Example: Election Results
Java Programming: From Problem Analysis to Program Design, Second Edition

39. Programming Example: Election Results
Java Programming: From Problem Analysis to Program Design, Second Edition

40. Additional String Methods
Java Programming: From Problem Analysis to Program Design, Second Edition

41. Additional String Methods
Java Programming: From Problem Analysis to Program Design, Second Edition

42. Additional String Methods
Java Programming: From Problem Analysis to Program Design, Second Edition

43. Additional String Methods
Java Programming: From Problem Analysis to Program Design, Second Edition

44. Effects of Some String Methods
Java Programming: From Problem Analysis to Program Design, Second Edition

45. Programming Example: Pig Latin Strings
If string begins with a vowel, “-way” is appended to it.
If first character is not a vowel:
Add “-” to end.
Rotate characters until the first character is a vowel.
Append “ay.”
Input: String
Output: String in pig Latin
Java Programming: From Problem Analysis to Program Design, Second Edition

46. Programming Example: Pig Latin Strings (Solution)
Methods: isVowel, rotate, pigLatinString
Use methods to:
Get the string (str).
Find the pig Latin form of str by using the method pigLatinString.
Output the pig Latin form of str.
Java Programming: From Problem Analysis to Program Design, Second Edition

47. Programming Example: Pig Latin Strings (Sample Runs)
Java Programming: From Problem Analysis to Program Design, Second Edition

48. Chapter Summary Lists Searching lists: Sorting lists:
Sequential searching
Sequential searching on an order list
Binary search
Sorting lists:
Bubble sort
Selection sort
Insertion sort
Java Programming: From Problem Analysis to Program Design, Second Edition

49. Chapter Summary Programming examples The class Vector The class String
Members of the class Vector
The class String
Additional methods of the class String
Java Programming: From Problem Analysis to Program Design, Second Edition