1. Visual C++ Programming: Concepts and Projects
Chapter 9A: Sorting
(Concepts)

2. Programming with Visual C++
Objectives
In this chapter, you will:
Create and use a Swap() method to exchange data values in arrays
Use nested loops to sort elements in an array
Implement a selection sort algorithm
Learn about the bubble sort technique
Programming with Visual C++

3. Objectives (continued)
Learn about the insertion sort technique
Analyze the complexity and efficiency of a sorting algorithm (big-O)
Programming with Visual C++

4. Exchanging Data Values in an Array
Two ways to put data into order
Data ordered from lowest to highest values is in ascending order
Data ordered from highest to lowest is in descending order
To sort data, you must be able to exchange (swap) values
Programming with Visual C++

5. Exchanging Data Values in an Array (continued)
Programming with Visual C++

6. Exchanging Data Values in an Array (continued)
Swapping requires a temporary variable and three steps
Programming with Visual C++

7. Exchanging Data Values in an Array (continued)
The code for a Swap() method
Programming with Visual C++

8. Exchanging Data Values in an Array (continued)
Programming with Visual C++

9. Exchanging Data Values in an Array (continued)
Programming with Visual C++

10. Exchanging Data Values in an Array (continued)
Programming with Visual C++

11. Exchanging Data Values in an Array (continued)
Programming with Visual C++

12. Programming with Visual C++
Sorting Strategies
This chapter investigates three methods of sorting data
Selection sort
Bubble sort
Insertion sort
All of these use nested loops
Programming with Visual C++

13. Sorting Strategies (continued)
Programming with Visual C++

14. Sorting Strategies (continued)
All of the sorting methods
Make a series of passes through the elements of an array
After each pass, one value has been moved to its correct, final position
The sorted portion of the array grows as the unsorted portion shrinks
Programming with Visual C++

15. Sorting Strategies (continued)
Programming with Visual C++

16. Programming with Visual C++
The Selection Sort
Start with an unsorted array
Find the smallest value in the unsorted portion of the array
Swap the smallest value with the first value in the unsorted portion of the array
Repeat the process until all of the values in the array have been processed
Programming with Visual C++

17. The Selection Sort (continued)
Programming with Visual C++

18. The Selection Sort (continued)
The outer loop executes n-1 times
Assign the location of the first element in the unsorted portion of the list to smallIndex
Find the location of the smallest element in the unsorted array
Swap the smallest element with the first unsorted value
Programming with Visual C++

19. The Selection Sort’s Inner Loop: Locating the Smallest Unsorted Value
Variables needed for the selection sort
Programming with Visual C++

20. Programming with Visual C++
The Selection Sort’s Inner Loop: Locating the Smallest Unsorted Value (continued)
The most important variable is smallIndex
It stores the location (index value) of the smallest value identified up to that point
smallIndex starts out set to 0, meaning that the smallest element so far is in array element [0]
If another array element contains a value smaller than element [0], then smallIndex is set to the location of that element
Programming with Visual C++

21. Programming with Visual C++
The Selection Sort’s Inner Loop: Locating the Smallest Unsorted Value (continued)
The inner loop accesses each element in the unsorted portion of the array
If the value stored in an element is less than the value stored in element [smallIndex], then assign the subscript to smallIndex
Programming with Visual C++

22. Programming with Visual C++
The Selection Sort’s Inner Loop: Locating the Smallest Unsorted Value (continued)
Programming with Visual C++

23. Programming with Visual C++
The Selection Sort’s Inner Loop: Locating the Smallest Unsorted Value (continued)
When the inner loop is finished:
Swap the following two values
The value stored in the first element in the unsorted portion of the array
The value stored in element [smallIndex]
Programming with Visual C++

24. Programming with Visual C++
The Selection Sort’s Inner Loop: Locating the Smallest Unsorted Value (continued)
Programming with Visual C++

25. Programming with Visual C++
The Bubble Sort
This strategy uses multiple swaps within the inner loop
It is analogous to the effervescence of bubbles in a glass
Bubbling action seems to rise from the bottom to the top
Data value exchanges decrease from the bottom of the array up as the sorting process executes
Programming with Visual C++

26. The Bubble Sort’s Inner Loop: Exchanging Values in Adjacent Elements
The outer loop executes n-1 times
The inner loop compares the values stored in each adjacent pair of elements in the unsorted portion of the array
If the value in the first element of the pair is greater than the value stored in the second element of the pair, then the two values are swapped
Programming with Visual C++

27. Programming with Visual C++
The Bubble Sort’s Inner Loop: Exchanging Values in Adjacent Elements (continued)
Programming with Visual C++

28. Programming with Visual C++
The Bubble Sort’s Inner Loop: Exchanging Values in Adjacent Elements (continued)
Programming with Visual C++

29. Programming with Visual C++
The Bubble Sort’s Inner Loop: Exchanging Values in Adjacent Elements (continued)
Bubble sort code
Programming with Visual C++

30. Programming with Visual C++
The Insertion Sort
Analogous to the method used to arrange cards in a hand
Strategy: sort from left to right
Look at the first value in the unsorted portion of the array
Compare it to all values in the sorted portion of the array
Insert the value into its correct position
Programming with Visual C++

31. The Insertion Sort (continued)
Programming with Visual C++

32. The Insertion Sort (continued)
Algorithm for the insertion sort of cards
Sorting moves from left to right
Programming with Visual C++

33. Programming with Visual C++

34. The Insertion Sort (continued)
Programming with Visual C++

35. Programming with Visual C++

36. Programming with Visual C++

37. The Insertion Sort (continued)
Programming with Visual C++

38. The Insertion Sort (continued)
Insertion sort algorithm
Programming with Visual C++

39. The Insertion Sort’s Inner Loop: Shifting Data Through Reassignment
The outer loop uses loop control variable i
Select the first value in the unsorted portion of the array
Temporarily “remove it from the list” by making a copy
Programming with Visual C++

40. Programming with Visual C++
The Insertion Sort’s Inner Loop: Shifting Data Through Reassignment (continued)
Array element from which the unsorted item was “removed” into temp can now be considered vacant
Programming with Visual C++

41. Programming with Visual C++
The Insertion Sort’s Inner Loop: Shifting Data Through Reassignment (continued)
The inner loop
Start with the last element in the sorted portion of the array
If the value in the sorted portion is greater than the one “removed from the list” (temp):
Then assign the value to the next highest element in the array (slide it down the array, opening up a vacancy)
Programming with Visual C++

42. Programming with Visual C++
The Insertion Sort’s Inner Loop: Shifting Data Through Reassignment (continued)
The inner loop
If the value in the sorted portion is NOT greater than the one “removed from the list” (temp) :
Then assign the value to the vacancy
data[vacant] = temp;
Programming with Visual C++

43. Programming with Visual C++
The Insertion Sort’s Inner Loop: Shifting Data Through Reassignment (continued)
Programming with Visual C++

44. Comparing Sorting Algorithms
Worst-case scenario
Selection sort
Outer loop x inner loop is O(n2) comparisons
Outer loop is O(n) exchanges
Bubble sort
Outer loop x inner loop is O(n2) exchanges
Insertion sort
Programming with Visual C++

45. Programming with Visual C++
Summary
Data may be sorted in ascending or descending order
Sorting frequently requires data value exchanges (swapping)
Sorting strategies covered in this chapter
Selection sort
Bubble sort
Insertion sort
Programming with Visual C++

46. Programming with Visual C++
Summary (continued)
The ascending order selection sort
Searches for the smallest value in the unsorted portion of the array and swaps it with the first value
The ascending order bubble sort
Compares values stored in adjacent pairs of unsorted elements and swaps them if the first is larger than the second
The ascending order insertion sort
Compares each unsorted value to the sorted portion of the array and inserts it into position after sliding other elements down
Programming with Visual C++