1. Lecture 14
2D Arrays
Richard Gesick

2. 2D vs 1D Arrays
Still hold several values of the same type (homogeneous)
Still based on a slot number (the index number), but has two now
Still have instant access
Still Static

3. What 2D arrays look like . . . . . . 1 2 3 4 5 6 myArray 1 2 3 4 5 61 2 3 4 5 6
[0,0]
[0,1]
[0,2]
[0,3]
[0,4]
[0,5]
[0,6]
myArray 1
[1,0]
[1,1]
[1,2]
[1,3]
[1,4]
[1,5]
[1,6] 2
[2,0]
[2,1]
[2,2]
[2,3]
[2,4]
[2,5]
[2,6] . . . 3
[3,0]
[3,1]
[3,2]
[3,3]
[3,4]
[3,5]
[3,6] 4
[4,0]
[4,1]
[4,2]
[4,3]
[4,4]
[4,5]
[4,6] 5
[5,0]
[5,1]
[5,2]
[5,3]
[5,4]
[5,5]
[5,6] 6
[6,0]
[6,1]
[6,2]
[6,3]
[6,4]
[6,5]
[6,6] . . .

4. Creating 2D Arrays Notice The comma The columns and rows values
<data type>[,] <name> = new <data type> [<rows>,<cols>];
Notice
The comma
The columns and rows values

5. Examples An array of shorts: An array of floats: An array of booleans:
short[,] someArray = new short[50,5];
An array of floats:
float[,] myArray = new float[25,10];
An array of booleans:
bool[,] list = new bool[640,480];
An array of chars:
char[,] characters = new char[2,2];

6. Modifying a 2D Array myArray[2,3] = 42 1 2 3 4 5 6 myArray 1 2 3 4 5 61 2 3 4 5 6
[0,0]
[0,1]
[0,2]
[0,3]
[0,4]
[0,5]
[0,6]
myArray 1
[1,0]
[1,1]
[1,2]
[1,3]
[1,4]
[1,5]
[1,6] 2
[2,0]
[2,1]
[2,2]
[2,3]
[2,4]
[2,5]
[2,6] 3
[3,0]
[3,1]
[3,2]
[3,3]
[3,4]
[3,5]
[3,6] 4
[4,0]
[4,1]
[4,2]
[4,3]
[4,4]
[4,5]
[4,6] 5
[5,0]
[5,1]
[5,2]
[5,3]
[5,4]
[5,5]
[5,6] 6
[6,0]
[6,1]
[6,2]
[6,3]
[6,4]
[6,5]
[6,6]
myArray[2,3] = 42

7. Iterating Through 2D Arrays
Working with 2D arrays, you will use two loops (nested)
Example:
byte[,] myPic = new byte[480,640];
for (int x=0; x < 480; x++) {
for (int y=0; y < 640; y++) {
myPic[x,y] = 0; }

8. Line by Line (a smaller example)
byte[,] myPic = new byte[3,3]; for (int x=0; x < 3; x++) { for (int y=0; y < 3; y++) { myPic[x,y] = 1; }

9. Line by Line (a smaller example)
byte[,] myPic = new byte[3,3]; for (int x=0; x < 3; x++) { for (int y=0; y < 3; y++) { myPic[x,y] = 1; }
myPic 1 2 1 2

10. Line by Line (a smaller example)
byte[,] myPic = new byte[3,3]; for (int x=0; x < 3; x++) { for (int y=0; y < 3; y++) { myPic[x,y] = 1; } 1 2
myPic x 1 2

11. Line by Line (a smaller example)
byte[,] myPic = new byte[3,3]; for (int x=0; x < 3; x++) { for (int y=0; y < 3; y++) { myPic[x,y] = 1; } 1 2
myPic x 1 2

12. Line by Line (a smaller example)
byte[,] myPic = new byte[3,3]; for (int x=0; x < 3; x++) { for (int y=0; y < 3; y++) { myPic[x,y] = 1; } 1 2
myPic x 1 y 2

13. Line by Line (a smaller example)
byte[,] myPic = new byte[3,3]; for (int x=0; x < 3; x++) { for (int y=0; y < 3; y++) { myPic[x,y] = 1; } 1 2
myPic x 1 y 2

14. Line by Line (a smaller example)
byte[,] myPic = new byte[3,3]; for (int x=0; x < 3; x++) { for (int y=0; y < 3; y++) { myPic[x,y] = 1; } 1 2
myPic x
What happens? 1 y 2

15. Line by Line (a smaller example)
byte[,] myPic = new byte[3,3]; for (int x=0; x < 3; x++) { for (int y=0; y < 3; y++) { myPic[x,y] = 1; } 1 2
myPic 1 x 1 y 2

16. Line by Line (a smaller example)
byte[,] myPic = new byte[3,3]; for (int x=0; x < 3; x++) { for (int y=0; y < 3; y++) { myPic[x,y] = 1; } 1 2
myPic 1 x 1 1 y 2

17. Line by Line (a smaller example)
byte[,] myPic = new byte[3,3]; for (int x=0; x < 3; x++) { for (int y=0; y < 3; y++) { myPic[x,y] = 1; } 1 2
myPic 1 x 1 1 2 y

18. Line by Line (a smaller example)
byte[,] myPic = new byte[3,3]; for (int x=0; x < 3; x++) { for (int y=0; y < 3; y++) { myPic[x,y] = 1; } 1 2
myPic 1 1 x 1 1 y 2

19. Line by Line (a smaller example)
byte[,] myPic = new byte[3,3]; for (int x=0; x < 3; x++) { for (int y=0; y < 3; y++) { myPic[x,y] = 1; }
myPic 1 2 1 1 x 1 2 y 2

20. Line by Line (a smaller example)
byte[,] myPic = new byte[3,3]; for (int x=0; x < 3; x++) { for (int y=0; y < 3; y++) { myPic[x,y] = 1; } 1 2
myPic 1 1 x 1 2 y 2

21. Line by Line (a smaller example)
byte[,] myPic = new byte[3,3]; for (int x=0; x < 3; x++) { for (int y=0; y < 3; y++) { myPic[x,y] = 1; } 1 2
myPic 1 1 1 x 1 2 y 2

22. Line by Line (a smaller example)
byte[,] myPic = new byte[3,3]; for (int x=0; x < 3; x++) { for (int y=0; y < 3; y++) { myPic[x,y] = 1; } 1 2
myPic 1 1 1 x 1 2 y 2

23. Line by Line (a smaller example)
byte[,] myPic = new byte[3,3]; for (int x=0; x < 3; x++) { for (int y=0; y < 3; y++) { myPic[x,y] = 1; } 1 2
myPic 1 1 1 x 1 3 y 2

24. Line by Line (a smaller example)
byte[,] myPic = new byte[3,3]; for (int x=0; x < 3; x++) { for (int y=0; y < 3; y++) { myPic[x,y] = 1; } 1 2
myPic 1 1 1 x 1 3 y 2

25. Line by Line (a smaller example)
byte[,] myPic = new byte[3,3]; for (int x=0; x < 3; x++) { for (int y=0; y < 3; y++) { myPic[x,y] = 1; } 1 2
myPic 1 1 1 1 x 1 2

26. Line by Line (a smaller example)
byte[,] myPic = new byte[3,3]; for (int x=0; x < 3; x++) { for (int y=0; y < 3; y++) { myPic[x,y] = 1; } 1 2
myPic 1 1 1 1 x 1 2

27. Line by Line (a smaller example)
byte[,] myPic = new byte[3,3]; for (int x=0; x < 3; x++) { for (int y=0; y < 3; y++) { myPic[x,y] = 1; } 1 2
myPic 1 1 1 1 x 1 y 2

28. Line by Line (a smaller example)
byte[,] myPic = new byte[3,3]; for (int x=0; x < 3; x++) { for (int y=0; y < 3; y++) { myPic[x,y] = 1; } 1 2
myPic 1 1 1 1 x 1 y 2

29. Line by Line (a smaller example)
byte[,] myPic = new byte[3,3]; for (int x=0; x < 3; x++) { for (int y=0; y < 3; y++) { myPic[x,y] = 1; } 1 2
myPic 1 1 1 1 x 1 1 y 2

30. Line by Line (a smaller example)
byte[,] myPic = new byte[3,3]; for (int x=0; x < 3; x++) { for (int y=0; y < 3; y++) { myPic[x,y] = 1; } 1 2
myPic 1 1 1 1 x 1 1 1 y 2

31. Now skipping ahead a bit

32. Line by Line (a smaller example)
byte[,] myPic = new byte[3,3]; for (int x=0; x < 3; x++) { for (int y=0; y < 3; y++) { myPic[x,y] = 1; } 1 2
myPic 1 1 1 2 1 1 1 1 x 2 1 1 1 y

33. Line by Line (a smaller example)
byte[,] myPic = new byte[3,3]; for (int x=0; x < 3; x++) { for (int y=0; y < 3; y++) { myPic[x,y] = 1; } 1 2
myPic 1 1 1 2 x 1 1 1 1 2 2 1 1 y

34. Line by Line (a smaller example)
byte[,] myPic = new byte[3,3]; for (int x=0; x < 3; x++) { for (int y=0; y < 3; y++) { myPic[x,y] = 1; } 1 2
myPic 1 1 1 2 x 1 1 1 1 2 2 1 1 y

35. Line by Line (a smaller example)
byte[,] myPic = new byte[3,3]; for (int x=0; x < 3; x++) { for (int y=0; y < 3; y++) { myPic[x,y] = 1; } 1 2
myPic 1 1 1 2 x 1 1 1 1 2 2 1 1 1 y

36. Line by Line (a smaller example)
byte[,] myPic = new byte[3,3]; for (int x=0; x < 3; x++) { for (int y=0; y < 3; y++) { myPic[x,y] = 1; } 1 2
myPic 1 1 1 1 1 1 1 2 x 2 1 1 1 3 y

37. Line by Line (a smaller example)
byte[,] myPic = new byte[3,3]; for (int x=0; x < 3; x++) { for (int y=0; y < 3; y++) { myPic[x,y] = 1; } 1 2
myPic 1 1 1 1 1 1 1 2 x 2 1 1 1 3 y

38. Line by Line (a smaller example)
byte[,] myPic = new byte[3,3]; for (int x=0; x < 3; x++) { for (int y=0; y < 3; y++) { myPic[x,y] = 1; } 1 2
myPic 1 1 1 1 1 1 1 3 x 2 1 1 1

39. Line by Line (a smaller example)
byte[,] myPic = new byte[3,3]; for (int x=0; x < 3; x++) { for (int y=0; y < 3; y++) { myPic[x,y] = 1; } 1 2
myPic 1 1 1 3 1 1 1 1 x 2 1 1 1

40. Done!
byte[,] myPic = new byte[3,3]; for (int x=0; x < 3; x++) { for (int y=0; y < 3; y++) { myPic[x,y] = 1; } 1 2
myPic 1 1 1 . . 1 1 1 1 . 2 1 1 1

41. Summary 2D Arrays are similar to 1D arrays
Usually requires nested loops