1. 2D Arrays Just another data structure Typically use a nested loop
A “grid”
Similar to 1D arrays (indices, static, contiguous)
Add another dimension
Hold 2D terrain
Typically use a nested loop
Find min/max/sum/average
Print out each element

2. int[,] grid = new int[4, 4];

3. int[,] grid = new int[4, 4];
<data type>[,] <name> = new <data type>[WIDTH, HEIGHT];

4. int[,] grid = new int[4, 4]; 4 4

5. int[,] grid = new int[4, 4];
How do we initialize this?

6. for (int y = 0; y < 4; y++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) { } y

7. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x y

8. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x x y y

9. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x x y 1 y

10. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x x y 1 y

11. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x x y 2 y

12. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x x y 2 y

13. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x x y 3 y

14. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x x y 3 y

15. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x y 4 y

16. false! int[,] grid = new int[4, 4]; for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; }
false! x y 4

17. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } y 1 y

18. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x x y 1 y

19. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x x y 1 y

20. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x x y 1 1 y

21. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x x y 1 1 y 1

22. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x x y 2 1 y 1

23. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x x y 2 1 y 1 2

24. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x x y 3 1 y 1 2

25. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x x y 3 1 y 1 2 3

26. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x y 4 1 y 1 2 3

27. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x y 4 1 y 1 2 3

28. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } y 2 1 2 3 y

29. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x x y 2 1 2 3 y

30. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x x y 2 1 2 3 y

31. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x x y 1 2 1 2 3 y

32. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x x y 1 2 1 2 3 y 2

33. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x x y 2 2 1 2 3 y 2

34. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x x y 2 2 1 2 3 y 2 4

35. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x x y 3 2 1 2 3 y 2 4

36. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x x y 3 2 1 2 3 y 2 4 6

37. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x y 4 2 1 2 3 y 2 4 6

38. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x y 4 2 1 2 3 y 2 4 6

39. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } y 3 1 2 3 2 4 6 y

40. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x x y 3 1 2 3 2 4 6 y

41. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x x y 3 1 2 3 2 4 6 y

42. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x x y 1 3 1 2 3 2 4 6 y

43. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x x y 1 3 1 2 3 2 4 6 y 3

44. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x x y 2 3 1 2 3 2 4 6 y 3

45. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x x y 2 3 1 2 3 2 4 6 y 3 6

46. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x x y 3 3 1 2 3 2 4 6 y 3 6

47. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x x y 3 3 1 2 3 2 4 6 y 3 6 9

48. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x y 4 3 1 2 3 2 4 6 y 3 6 9

49. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } x y 4 3 1 2 3 2 4 6 y 3 6 9

50. for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) {
int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; } y 4 1 2 3 2 4 6 3 6 9

51. false! int[,] grid = new int[4, 4]; for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; }
false! y 4 1 2 3 2 4 6 3 6 9

52. int[,] grid = new int[4, 4];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
grid[x, y] = x*y; }
// Continue processing 1 2 3 2 4 6 3 6 9

53. Finding the Smallest int smallest = grid[0,0];
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
if (smallest > grid[x, y]) {
smallest = grid[x, y]; }

54. Finding the Sum int sum = 0; for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
sum += grid[x, y]; }

55. Finding the Average int sum = 0; for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
sum += grid[x, y]; }
double average = sum/16.0f;

56. Things to Note All of these examples had a nested loop
Only the logic changed!
2D arrays are similar to 1D arrays