An explanation of how an insertion sort works. (Created for my Yr 12 Software Design and Development class.)

1. Insertion Sort
9 72 5 1 4 3 6

2. Insertion Sort
9 72 5 1 4 3 6
Sorted
section
We start by dividing the array in a section section and an unsorted
section. We put the first element as the only element in the sorted
section, and the rest of the array is the unsorted section.

3. Insertion Sort
9 72 5 1 4 3 6
Sorted
section
Item to
position
The first element in the unsorted section is the
next element to be put into the correct position.

4. Insertion Sort
9 7
2
5 1 4 3 6
Item to
position
2
We copy the element to be placed into
another variable so it doesn’t get overwritten.

5. Insertion Sort
9 7
2
5 1 4 3 62
compare
If the previous position is more than the item being
placed, copy the value into the next position

6. Insertion Sort
9 7
2
5 1 4 3 69
If there are no more items in the sorted section to
compare with, the item to be placed must go at the front.
belongs here

7. Insertion Sort
9 72 5 1 4 3 6

8. Insertion Sort
9 72 5 1 4 3 6

9. Insertion Sort
9 72 5 1 4 3 6
Item to
position

10. Insertion Sort
9
7
2 5 1 4 3 67
compare

11. Insertion Sort
9
7
2 5 1 4 3 6
Copied from
previous position
9
compare
If the item in the sorted section is less than the item to
place, the item to place goes after it in the array.
belongs here

12. Insertion Sort
972 5 1 4 3 6

13. Insertion Sort
972 5 1 4 3 6

14. Insertion Sort
972 5 1 4 3 6
Item to
position

15. Insertion Sort
972
5
1 4 3 65
compare

16. Insertion Sort
972
5
1 4 3 69
compare

17. Insertion Sort
972
5
1 4 3 67
compare
belongs here

18. Insertion Sort
972 5 1 4 3 6

19. Insertion Sort
972 5 1 4 3 6

20. Insertion Sort
972 5 1 4 3 6
Item to
position

21. Insertion Sort
972 5
1
4 3 61
compare

22. Insertion Sort
972 5
1
4 3 69
compare

23. Insertion Sort
972 5
1
4 3 67
compare

24. Insertion Sort
972 5
1
4 3 65
compare

25. Insertion Sort
972 5
1
4 3 62
belongs here

26. Insertion Sort
972 51 4 3 6

27. Insertion Sort
972 51 4 3 6

28. Insertion Sort
972 51 4 3 6
Item to
position

29. Insertion Sort
972 51
4
3 64
compare

30. Insertion Sort
972 51
4
3 69
compare

31. Insertion Sort
972 51
4
3 67
compare

32. Insertion Sort
972 51
4
3 6
belongs here
5
compare

33. Insertion Sort
972 51 4 3 6

34. Insertion Sort
972 51 4 3 6

35. Insertion Sort
972 51 4 3 6
Item to
position

36. Insertion Sort
972 51 4
3
63
compare

37. Insertion Sort
972 51 4
3
69
compare

38. Insertion Sort
972 51 4
3
67
compare

39. Insertion Sort
972 51 4
3
65
compare

40. Insertion Sort
972 51 4
3
64
compare
belongs here

41. Insertion Sort
972 51 43 6

42. Insertion Sort
972 51 43 6

43. Insertion Sort
972 51 43 6
Item to
position

44. Insertion Sort
972 51 43
6
6
compare

45. Insertion Sort
972 51 43
6
9
compare

46. Insertion Sort
972 51 43
6
7
compare
belongs here

47. Insertion Sort
972 51 43 6

48. Insertion Sort
972 51 43 6
SORTED!