Visual Basic 2008 9.0 .NET Examples and Ebook

It is possible to create an array of which the elements are references to other arrays. This is for instance useful when a collection of collections needs to be managed.

Next example declares a array cities with two elements of type Array.
These elements can now hold a reference to any type of array. cities(0) holds a reference to a one-dimensional String array (1). cities(1) holds a reference to a one-dimensional Integer array (2).

Module Example
    Sub Main()
        Dim names() As String = {"Brussels", "Antwerp", "Ghent"}
        Dim zipCodes() As Integer = {1000, 2000, 0}
        '
        Dim cities(1) As Array
        cities(0) = names                                                  ' (1)
        cities(1) = zipCodes                                               ' (2)
        ' or : Dim cities As Array() = {names, zipCodes}
        '
        Console.WriteLine(names(1))                                        ' (3)
        Console.WriteLine(cities(0)(1))                                    ' (4)
        '
        cities(1)(2) = 9000
        Console.WriteLine(zipCodes(2))                                     ' (5)
        '
        Console.ReadLine()
    End Sub
End Module

Output :

 Antwerp
 Antwerp
 9000

As you can see on lines (3) and (4) expressions names and cities(0) both evaluate to the reference of the array instance containing the names of the cities. So expressions names(1) and cities(0)(1) both address the second element of the same array.

Task :

Make a program containing 3 arrays :
- a one-dimensional String array containing names of students
- a one-dimensional Integer array containing scores of students
- a jagged array, with 2 elements, pointing to the previous two arrays

Try for exercise only to use the jagged array to address the names and scores of the students, so avoid using the first 2 arrays.

Make it possible to add students and their scores. The program calculates and stores the averages score for each student. Store this average score in an extra row or column of the scores-array.

Output :

 Student Count ? 2
 Topic Count ? 2

 Name Student 1 ? John
 John Score Topic 1 ? 4
 John Score Topic 2 ? 6

 Name Student 2 ? Paul
 Paul Score Topic 1 ? 6
 Paul Score Topic 2 ? 8

 Name : John
 Score Topic 1 : 4
 Score Topic 2 : 6
 Average Score : 5

 Name : Paul
 Score Topic 1 : 6
 Score Topic 2 : 8
 Average Score : 7

Solution :

Module ExerciseSolution
    Sub Main()
        Console.Write("Student Count ? ")
        Dim studentCount As Integer = Console.ReadLine()
        Console.Write("Topic Count ? ")
        Dim topicCount As Integer = Console.ReadLine()
        Console.WriteLine()
        '
        Dim studentUpperbound As Integer = studentCount - 1
        Dim names(studentUpperbound) As String
        Dim topicUpperbound As Integer = topicCount
        Dim scores(studentUpperbound, topicUpperbound) As Double
        Dim students(1) As Array
        Const namesIndex As Integer = 0, scoresIndex As Integer = 1
        students(namesIndex) = names
        students(scoresIndex) = scores
        '
        Dim studentIndex, topicIndex As Integer
        For studentIndex = 0 To studentUpperbound
            Console.Write("Name Student " & (studentIndex + 1) & " ? ")
            students(namesIndex)(studentIndex) = Console.ReadLine()
            For topicIndex = 0 To topicUpperbound - 1
                Console.Write(students(namesIndex)(studentIndex) & _
                              " Score Topic " & (topicIndex + 1) & " ? ")
                students(scoresIndex)(studentIndex, topicIndex) = _
                                                              Console.ReadLine()
            Next
            Console.WriteLine()
        Next
        '
        For studentIndex = 0 To studentUpperbound
            For topicIndex = 0 To topicUpperbound - 1
                students(scoresIndex)(studentIndex, topicUpperbound) += _
                      students(scoresIndex)(studentIndex, topicIndex)
            Next
            students(scoresIndex)(studentIndex, topicUpperbound) /= _
                                                                 topicUpperbound
        Next
        '
        Console.WriteLine()
        For studentIndex = 0 To studentUpperbound
            Console.WriteLine("Name : " & students(namesIndex)(studentIndex))
            For topicIndex = 0 To topicUpperbound - 1
                Console.WriteLine("Score Topic " & (topicIndex + 1) & " : " & _
                                students(scoresIndex)(studentIndex, topicIndex))
            Next
            Console.WriteLine("Average Score : " & _
                           students(scoresIndex)(studentIndex, topicUpperbound))
            Console.WriteLine()
        Next
        '
        Console.ReadLine()
    End Sub
End Module