1. Sorting CSCE 121 J. Michael Moore
Based on slides created by Carlos Soto.

2. Sorting Algorithms There are lots of ways to sort
you will implement several in CSCE 221
C++ STL has built in sorting
So do many other languages
Still very useful to know how to implement
Good first algorithm to code
Even a small amount of code can be tricky

3. Selection Sort Start with an ‘empty’ list.
While we still have values to insert,
Find smallest value and put at end of list.
Outer Loop
Inner Loop

4. Selection Sort Start with an ‘empty’ list.
Smallest
Start with an ‘empty’ list.
While we still have values to insert,
Find smallest value and put at end of list.
Insert 1 2 3 4 5 6 7 8 27 1 93 2 42 3 77 4 19 5 55 6
212 7 32 8
111

5. Selection Sort Start with an ‘empty’ list.
While we still have values to insert,
Find smallest value and put at end of list.
Insert 1 2 3 4 5 6 7 8 27 1 93 2 42 3 77 4 19 5 55 6
212 7 32 8
111
Smallest

6. Selection Sort Start with an ‘empty’ list.
Smallest
Start with an ‘empty’ list.
While we still have values to insert,
Find smallest value and put at end of list. 19 1 2 3 4 5 6 7 8 27 1 93 2 42 3 77 4 55 5
212 6 32 7
111 8
Insert

7. Selection Sort Start with an ‘empty’ list.
Smallest
Start with an ‘empty’ list.
While we still have values to insert,
Find smallest value and put at end of list. 19 1 2 3 4 5 6 7 8 27 1 93 2 42 3 77 4 55 5
212 6 32 7
111 8
Insert

8. Selection Sort Start with an ‘empty’ list.
Smallest
Start with an ‘empty’ list.
While we still have values to insert,
Find smallest value and put at end of list. 19 1 27 2 3 4 5 6 7 8 93 1 42 2 77 3 55 4
212 5 32 6
111 7 8
Insert

9. Selection Sort Start with an ‘empty’ list.
While we still have values to insert,
Find smallest value and put at end of list. 19 1 27 2 3 4 5 6 7 8 93 1 42 2 77 3 55 4
212 5 32 6
111 7 8
Insert
Smallest

10. Selection Sort Start with an ‘empty’ list.
Smallest
Start with an ‘empty’ list.
While we still have values to insert,
Find smallest value and put at end of list. 19 1 27 2 32 3 4 5 6 7 8 93 1 42 2 77 3 55 4
212 5
111 6 7 8
Insert

11. Selection Sort Start with an ‘empty’ list.
While we still have values to insert,
Find smallest value and put at end of list. 19 1 27 2 32 3 4 5 6 7 8 93 1 42 2 77 3 55 4
212 5
111 6 7 8
Smallest
Insert

12. Selection Sort Start with an ‘empty’ list.
Smallest
Start with an ‘empty’ list.
While we still have values to insert,
Find smallest value and put at end of list. 19 1 27 2 32 3 42 4 5 6 7 8 93 1 77 2 55 3
212 4
111 5 6 7 8
Insert

13. Selection Sort Start with an ‘empty’ list.
While we still have values to insert,
Find smallest value and put at end of list. 19 1 27 2 32 3 42 4 5 6 7 8 93 1 77 2 55 3
212 4
111 5 6 7 8
Smallest
Insert

14. Selection Sort Start with an ‘empty’ list.
Smallest
Start with an ‘empty’ list.
While we still have values to insert,
Find smallest value and put at end of list. 19 1 27 2 32 3 42 4 55 5 6 7 8 93 1 77 2
212 3
111 4 5 6 7 8
Insert

15. Selection Sort Start with an ‘empty’ list.
While we still have values to insert,
Find smallest value and put at end of list. 19 1 27 2 32 3 42 4 55 5 6 7 8 93 1 77 2
212 3
111 4 5 6 7 8
Smallest
Insert

16. Selection Sort Start with an ‘empty’ list.
Smallest
Start with an ‘empty’ list.
While we still have values to insert,
Find smallest value and put at end of list. 19 1 27 2 32 3 42 4 55 5 77 6 7 8 93 1
212 2
111 3 4 5 6 7 8
Insert

17. Selection Sort Start with an ‘empty’ list.
Smallest
Start with an ‘empty’ list.
While we still have values to insert,
Find smallest value and put at end of list. 19 1 27 2 32 3 42 4 55 5 77 6 7 8 93 1
212 2
111 3 4 5 6 7 8
Insert

18. Selection Sort Start with an ‘empty’ list.
Smallest
Start with an ‘empty’ list.
While we still have values to insert,
Find smallest value and put at end of list. 19 1 27 2 32 3 42 4 55 5 77 6 93 7 8
212 1
111 2 3 4 5 6 7 8
Insert

19. Selection Sort Start with an ‘empty’ list.
While we still have values to insert,
Find smallest value and put at end of list. 19 1 27 2 32 3 42 4 55 5 77 6 93 7 8
212 1
111 2 3 4 5 6 7 8
Smallest
Insert

20. Selection Sort Start with an ‘empty’ list.
Smallest
Start with an ‘empty’ list.
While we still have values to insert,
Find smallest value and put at end of list. 19 1 27 2 32 3 42 4 55 5 77 6 93 7
111 8
212 1 2 3 4 5 6 7 8
Insert

21. Selection Sort Start with an ‘empty’ list.
Smallest
Start with an ‘empty’ list.
While we still have values to insert,
Find smallest value and put at end of list. 19 1 27 2 32 3 42 4 55 5 77 6 93 7
111 8
212 1 2 3 4 5 6 7 8
Insert

22. Selection Sort Start with an ‘empty’ list.
Smallest
Start with an ‘empty’ list.
While we still have values to insert,
Find smallest value and put at end of list. 19 1 27 2 32 3 42 4 55 5 77 6 93 7
111 8
212 1 2 3 4 5 6 7 8
Insert

23. Selection Sort Sorted! Start with an ‘empty’ list.
While we still have values to insert,
Find smallest value and put at end of list. 19 1 27 2 32 3 42 4 55 5 77 6 93 7
111 8
212 1 2 3 4 5 6 7 8

24. Improve? Created a second vector.
Do we have to?
NO!
Keep sorted list and remaining items to place in the same vector.
When we start
the sorted list has size 0 (zero)
the number of items to place is the size of the list
Start with the place to insert at zero
Find smallest starting from the place to insert
Swap smallest with item in the place to insert
Increment place to insert

25. Selection Sort (Second Version)
Set place to insert to first location in list
While we still have values to insert,
Find smallest value and swap with location to insert.
Increment place to insert

26. Selection Sort Set place to insert to first location in list
While we still have values to insert,
Find smallest value and swap with location to insert
Increment place to insert
Insert 27 1 93 2 42 3 77 4 19 5 55 6
212 7 32 8
111
Smallest
Items to search

27. Selection Sort Set place to insert to first location in list
While we still have values to insert,
Find smallest value and swap with location to insert
Increment place to insert
Insert 19 1 93 2 42 3 77 4 27 5 55 6
212 7 32 8
111
Smallest
Items to search

28. Selection Sort Set place to insert to first location in list
While we still have values to insert,
Find smallest value and swap with location to insert
Increment place to insert 19 1 93 2 42 3 77 4 27 5 55 6
212 7 32 8
111
Insert
Smallest
Items to search

29. Selection Sort Set place to insert to first location in list
While we still have values to insert,
Find smallest value and swap with location to insert
Increment place to insert 19 1 27 2 42 3 77 4 93 5 55 6
212 7 32 8
111
Insert
Smallest
Items to search

30. Selection Sort Set place to insert to first location in list
While we still have values to insert,
Find smallest value and swap with location to insert
Increment place to insert 19 1 27 2 42 3 77 4 93 5 55 6
212 7 32 8
111
Insert
Items to search
Smallest

31. Selection Sort Set place to insert to first location in list
While we still have values to insert,
Find smallest value and swap with location to insert. 19 1 27 2 32 3 77 4 93 5 55 6
212 7 42 8
111
Insert
Items to search
Smallest

32. Selection Sort Set place to insert to first location in list
While we still have values to insert,
Find smallest value and swap with location to insert. 19 1 27 2 32 3 77 4 93 5 55 6
212 7 42 8
111
Insert
Items to search
Smallest

33. Selection Sort Set place to insert to first location in list
While we still have values to insert,
Find smallest value and swap with location to insert. 19 1 27 2 32 3 42 4 93 5 55 6
212 7 77 8
111
Insert
Items to search
Smallest

34. Selection Sort Set place to insert to first location in list
While we still have values to insert,
Find smallest value and swap with location to insert
Increment place to insert 19 1 27 2 32 3 42 4 93 5 55 6
212 7 77 8
111
Insert
Smallest
Items to search

35. Selection Sort Set place to insert to first location in list
While we still have values to insert,
Find smallest value and swap with location to insert
Increment place to insert 19 1 27 2 32 3 42 4 55 5 93 6
212 7 77 8
111
Insert
Smallest
Items to search

36. Selection Sort Set place to insert to first location in list
While we still have values to insert,
Find smallest value and swap with location to insert
Increment place to insert 19 1 27 2 32 3 42 4 55 5 93 6
212 7 77 8
111
Insert
Items to search
Smallest

37. Selection Sort Set place to insert to first location in list
While we still have values to insert,
Find smallest value and swap with location to insert
Increment place to insert 19 1 27 2 32 3 42 4 55 5 77 6
212 7 93 8
111
Insert
Items to search
Smallest

38. Selection Sort Set place to insert to first location in list
While we still have values to insert,
Find smallest value and swap with location to insert
Increment place to insert 19 1 27 2 32 3 42 4 55 5 77 6
212 7 93 8
111
Insert
Smallest
Items to search

39. Selection Sort Set place to insert to first location in list
While we still have values to insert,
Find smallest value and swap with location to insert
Increment place to insert 19 1 27 2 32 3 42 4 55 5 77 6 93 7
212 8
111
Insert
Smallest
Items to search

40. Selection Sort Set place to insert to first location in list
While we still have values to insert,
Find smallest value and swap with location to insert
Increment place to insert 19 1 27 2 32 3 42 4 55 5 77 6 93 7
212 8
111
Insert
Items to search
Smallest

41. Selection Sort Set place to insert to first location in list
While we still have values to insert,
Find smallest value and swap with location to insert
Increment place to insert 19 1 27 2 32 3 42 4 55 5 77 6 93 7
111 8
212
Insert
Items to search
Smallest

42. Selection Sort
Since last item has to be in the right place, we actually stop before inserting into last location.
Set place to insert to first location in list
While we still have values to insert,
Find smallest value and swap with location to insert
Increment place to insert 19 1 27 2 32 3 42 4 55 5 77 6 93 7
111 8
212
Smallest
Items to search
Insert

43. Selection Sort Sorted! Set place to insert to first location in list
While we still have values to insert,
Find smallest value and swap with location to insert
Increment place to insert 19 1 27 2 32 3 42 4 55 5 77 6 93 7
111 8
212
Sorted!