VB Data Structures

1
VB Data Structures
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Atomic Variables

• Atomic variables can only store one value at a
  time.
• Dim fName As String
• Dim sName As String
• Dim age As Integer
• A value stored in an atomic variable cannot be
  subdivided.

3
Data Structures

• A data structure is a data type whose value can
  be composed of individual elements.
• Each element has a data type which can be
• Atomic.
• Data structure.

4
Arrays Re-visited

• An array is a special kind of data structure.
• It stores a list of related values of the same
  type.
• It is a homogeneous data structure.
• Such values can be accessed using a single
  variable name.
• Dim myArray(6) As Integer
• Creates an array containing --- elements, stored
  at indexes -----------

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Heterogeneous Data Structures

• Sometimes, we want to store values of different
  data types in one place.
• Cant use arrays.
• A data structure that can store different types
  in one variable is called a record.

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Structure Definition

• Structure Person
• Dim fName As String
• Dim sName As String
• Dim age As Integer
• End Structure
• The above definition creates a new data type
  named Person.
• It defines three structure members fName, sName,
  age.

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Using Structures

• To use a structure, a variable need to be
  declared having the structure data type.
• Dim person1 As Person
• Dim family(4) As Person
• To access structure members, use variable name
  and member name, separated by a period.
• person1.fName yussuf
• family(1).age 50

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Search a List Data StructureLinear Search

• For each item in the list
• Check to see if the item you're looking for
  matches the item in the list.
• If it matches.
• Return the location where you found it (the
  index).
• End of loop
• If we get here, we know the item does not exist
  in the list.
• Return -1.

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Linear Search Function

• Public Function linearSearch(ByVal persons() As
  Person, ByVal size As Integer, ByVal key As
  String) As Integer
• Dim index As Integer
• For index 0 To size
• if( String.compare(
  persons(index).sName, key) 0) Then
• Return index
• End If
• Next
• Return -1
• End Function
• Dim sample(2) As Person
• Dim match As Integer -2
• sample(0).sName "smith"
• sample(1).sName "hillman"
• sample(2).sName "McDonald"
• match linearSearch(sample, 2, hillman")

10
Binary Search

• List must be sorted.
• If x is the value we are looking for
• Compare X to the middle value of the list. If
  XY, (the middle element) we are done, return Ys
  index. If X lt Y, we continue our search confine
  the search to first half only. If X gt Y, we
  continue our search confine the search to second
  half.

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Binary Search Function

• Public Function binarySearch(ByVal list() As
  Integer, ByVal size As Integer, ByVal key As
  Integer) As Integer
• Dim left, right, middle As Integer
• left 0
• right size
• Do While left ltright
• middle Int( (left right) / 2)
• if key list(middle) Then
• Return middle
• ElseIf key gt list(middle) Then
• left middle 1
• Else
• right middle - 1
• End If
• Loop
• Return -1
• End Function

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Binary Search Test

• Dim sample(4) As Integer
• Dim match As Integer -1
• sample(0) 2
• sample(1) 5
• sample(2) 7
• sample(3) 10
• sample(4) 12
• match binarySearch(sample, 4, 5)