1. Arrays Group of variables that have a similar type
Integers
Strings
Doubles
An array of states, tax rates, social security numbers

2. Arrays
Arrays can be in one dimension or two dimensions (actually you can have up to 60 dimensions)
1D myarray(4) as string
can contain: NJ(0), NY(1), DE(2), PA(3)

3. Arrays 2D --- myarray(3,3) can contain a tic-tac-toe board:
X (0,0) O (0,1) X (0,2)
O X O
X (2,0) O (2,1) X (2,2)

4. Arrays
1D Array:
Dim arrayname(lower subscript TO upper subscript) as datatype
*** lower subscript is set to 0

5. Arrays - Examples Dim statearray(0 to 4) as string
Creates a string array that will contain state ids
Statearray(3) equals ‘DE’

6. Arrays - Examples Dim montharray(0 to 11) as string
Creates a string array that will contain months in the year

7. Arrays - Examples Dim numberarray(1 to 10) as Integer
Creates an integer array that will contain 10 numbers

8. Arrays - Examples no set range of elements
Dim ArrayVariable() as Integer
no set range of elements
Elements in this array are from 0 to n

9. Arrays - Examples For x = 0 to 4 myarray(x) = x+1
Dim myarray(5) as Integer
For x = 0 to 4
myarray(x) = x+1
Form1.Print “array(“ & x & “) = “ & array(x)
Next x

10. Arrays - Examples
Dim myarray(50) as string
myarray(0) = “hello”

11. Arrays - Examples 0 for numeric arrays spaces for string arrays
Valuing an array:
Default values of arrays are:
0 for numeric arrays
spaces for string arrays
false for boolean arrays  

12. Arrays - Examples Montharray(11) = “December” Numberarray(5) = 21
Valuing an array:
(element by element hard coded)
Montharray(11) = “December”
Numberarray(5) = 21

13. Arrays - Examples For x = 1 to 10
Valuing an array:
(use a loop)
For x = 1 to 10
Myarray(x) = Val(Inputbox(“Enter a _ Number”))
Next x

14. Arrays - Examples Dim myarray(5) as Integer For x = 1 to 5
For x = 1 to 5
Myarray(x) = x+1
Form1.Print “array(“ & x & “) = “ & array(x)
Next x

15. Arrays - Examples Getting array data:
Txt1.text = montharray(5) ‘ displays ‘ MAY
Text2.text = numberarray(5) ‘display 21

16. Arrays - Examples
PRACTICE: ZAK p. 724 “The Presidents” Write an application that allows a user to guess the first 10 US Presidents. Create a string array of the presidents (form load) and randomly ask the user to guess the 1st, 2nd, etc… president.
Continued...

17. Arrays - Examples PRACTICE: ZAK p. 724 “The Presidents”
Have them select from a radio button control array of 15 unordered presidents. One they click on a “GUESS” button, examine their choice and match it to the string array. Let them know if they are right or wrong and keep track of their choices. Once they successfully selected a president, disable that choice and DO NOT allow that number to be used again

18. Arrays - RANGES
Lbound --- identifies and returns the lowest index in the array
(usually 0)
Lbound(arrayname, DIM) ‘ DIM identifies the dimension of the array 1 is
‘ default
 EXAMPLE: Result = Lbound(myarray)

19. Arrays - RANGES
Ubound --- identifies and returns the highest index in the array
Ubound(arrayname, DIM) ‘ DIM identifies the dimension of the array 1 is default
EXAMPLE: Result = Ubound(myarray)
for x = 1 to Result …
Next x

20. Arrays - RANGES EXAMPLE: Dim mystring(10) as String
For count = Lbound(mystring) TO ubound(mystring)
mystring(count) = InputBox(“Enter a Name:”)
Next count

21. Arrays - RANGES EXAMPLE: RANGE Errors: Dim myarray(5) as integer
Myarray(6) = 200 ‘ SUBSCRIPT ERROR

22. Arrays - Unbounded Unbounded/Dynamic Array:
Declare an array with no predefined size. It can vary in size during run time.
Dim myarray() as Integer

23. Arrays - Redim
REDIM --- allocates/resets the size of an unbounded/dynamic array
Redim myarray(10) clears out the array and resizes it to the number of Elements
ONLY USE THIS ON LOCALLY SCOPED ARRAYS !!!

24. Arrays - Redim REDIM To Preserve the existing array when redimming:
Keeps existing values when redimming.
Can only do when resetting the UPPERBOUNDRY of the array.

25. Arrays - Redim REDIM Redim Preserve myarray(10)
preserves the existing contents of the array
Redim Preserve myarray Ubound(myarray) + 1)
dynamically adds 1 element to the array size

26. Arrays - Redim
REDIM
Erase --- deallocates an array space if its dynamically allocated. Reinitializes the elements of a fixed sized array.
Erase myarray

27. Arrays - Redim
PRACTICE: Thompson (p. 9-6) Count the freequency of dice roll outcomes

28. Arrays - Searching Searching and Array: Linear
Iterate thru each array element looking for a specifice value, Example:
‘ find a given number in an integer array
searchnum = 5
dim intarray(20) as integer
do while (intarray(I) <> searchnum) AND (I < Ubound(intarray))
I = I + 1
loop

29. Arrays - 2 D Array 2 Dimensional Array:
a matrix is a multidimensonal array used to store related information.
Checkerboard, tic-tac-toe board.

30. Arrays - 2 D Array Dim my2darray(3,3) as Integer
(X,Y) X = rows Y = columns
R 0,0 0,1 0,2 0,3
O 1,0 1,1 1,2 1,3
W 2,0 2,1 2,2 2,3
S 3,0 3,1 3,2 3,3
COLUMNS (Y)

31. Arrays - 2 D Array EXAMPLE: Dim a2d(3, 3) a2d(0, 0) = 1 a2d(2, 2) = 5

32. Bubble Sort For x = Lbound(array) to Ubound(array)
For y = Lbound(array) to Ubound(array)-1
if array(y) > array(y+1) then
temp = array(y)
array(y) = array(y+1)
array(y+1) = temp
end if
Next

33. Binary Search Dim lowi ,highi, midi as integer Lowi = Lbound(array)
Highi = Ubound(array)

34. Binary Search Do While Not boolfound AND lowi <= highi
midi = Int((highi + lowi) / 2)
if array(midi) = TARGETNUM then
boolfound = TRUE
elseif array(midi) > TARGETNUM then
highi = midi -1
else
lowi = mid + 1
end if
loop

35. Binary Search
If boolfound = TRUE then
“FOUND”
else
“NOT FOUND”
End if

36. ArrayList
The ArrayList is a “class” that allows you to maintain an “array” of objects and have the ArrayList do all of the organizing of the data.

37. ArrayList
You can perform the following types of actions with an ArrayList:
Add
Count
Remove
Sort
Search

38. ArrayList
You can perform the following types of actions with an ArrayList:
Get an Item from the list (Item)
Clear the list
Determine if 2 elements are EQUAL (equal)
Obtain the value at a specific index in the arraylist (IndexOf)

39. ArrayList
The following are examples on how to use each of these actions:

40. ArrayList
Create the ArrayList:
Dim myAL As ArrayList = New ArrayList

41. ArrayList Add elements to the ArrayList: Dim cc As Integer = 10
myAL.Add(cc)
myAL.Add(20)

42. ArrayList iterate thru all elements of the ArrayList (Count and Item):
Dim z As Integer
z = 0
Do While z < myAL.Count
Button3.Text = Val(Button3.Text) + myAL.Item(z)
z += 1
Loop

43. ArrayList
Remove elements from the ArrayList:
myAL.Remove(20)

44. ArrayList
Check the list to see if a specific ob ject is in the ArrayList:
TextBox1.Text = myAL.Contains(15)

45. ArrayList Return a specific element from the ArrayList:
myAL.Item(0) = 40

46. ArrayList
Sort elements of the ArrayList:
myAL.Sort()

47. ArrayList Search for an element in the ArrayList:
TextBox2.Text = myAL.BinarySearch(40)

48. ArrayList Check to see if 2 objects are equal:
TextBox3.Text = myAL(0).Equals(myAL(0))

49. ArrayList
Empty the ArrayList:
myAL.Clear()

50. PRACTICE: Thompson (p. 9-26) Exercise 3 “Generated Numbers”
PRACTICE: Thompson (p. 9-27) Exercise 5a “Generated Numbers” (5b advanced)
PRACTICE: Thompson (p. 9-28) Exercise 8 “Duplicate Values”
PRACTICE: Thompson (p. 9-29) Exercise 10 “Lockers”
continued...

51. PRACTICE: Thompson (p. 9-30) Exercise 12 “Game Board 16” (12b advanced)
PRACTICE: Thompson (p to 33) Exercises 13, 14, 15 and 16 (ADVANCED)