Type Pair
    primero As Integer
    segundo As Integer
End Type

Type Graph
    vertices(14) As String
    numVertices As Integer
    proximos(14, 14) As Boolean

    Declare Constructor(s As String, edges() As Pair)
    Declare Function hasDependency(r As Integer, todo() As Integer, todoCount As Integer) As Boolean
    Declare Function topoSort() As String
End Type

Function splitString(text As String, delimiter As String, Byref count As Integer) As String Ptr
    Dim As Integer numTokens = 0
    Dim As String tmp = text
    Dim As Long posic

    ' Count delimiters
    Do
        posic = Instr(tmp, delimiter)
        If posic = 0 Then Exit Do
        numTokens += 1
        tmp = Mid(tmp, posic + Len(delimiter))
    Loop
    numTokens += 1

    ' Allocate array
    count = numTokens
    Dim As String Ptr result = Callocate((numTokens) * Sizeof(String))

    ' Split string
    tmp = text
    numTokens = 0
    Do
        posic = Instr(tmp, delimiter)
        If posic = 0 Then
            result[numTokens] = tmp
            Exit Do
        End If
        result[numTokens] = Left(tmp, posic - 1)
        tmp = Mid(tmp, posic + Len(delimiter))
        numTokens += 1
    Loop

    Return result
End Function

Constructor Graph(s As String, edges() As Pair)
    Dim As Integer i, tokenCount
    Dim As String Ptr tokens = splitString(s, ", ", tokenCount)
    numVertices = tokenCount
    For i = 0 To numVertices - 1
        vertices(i) = tokens[i]
    Next
    Deallocate(tokens)

    ' Initialize proximos matrix
    For i = 0 To Ubound(edges)
        proximos(edges(i).primero, edges(i).segundo) = True
    Next
End Constructor

Function Graph.hasDependency(r As Integer, todo() As Integer, todoCount As Integer) As Boolean
    For i As Integer = 0 To todoCount - 1
        If proximos(r, todo(i)) Then Return True
    Next
    Return False
End Function

Function Graph.topoSort() As String
    Dim As String result = ""
    Dim As Integer todoCount, i, j
    Dim As Integer todo(numVertices)

    todoCount = numVertices
    ' Initialize todo list
    For i = 0 To numVertices - 1
        todo(i) = i
    Next

    While todoCount > 0
        i = 0
        Dim As Boolean found = False

        While i < todoCount
            If Not hasDependency(todo(i), todo(), todoCount) Then
                ' Add to result
                If Len(result) > 0 Then result &= ", "
                result &= vertices(todo(i))

                ' Remove from todo
                For j = i To todoCount - 2
                    todo(j) = todo(j + 1)
                Next
                todoCount -= 1
                found = True
                Exit While
            End If
            i += 1
        Wend

        If Not found Then Return "Graph has cycles"
    Wend

    Return "[" & result & "]"
End Function

' Main program
Dim As String s = "std, ieee, des_system_lib, dw01, dw02, dw03, dw04, dw05, " & _
"dw06, dw07, dware, gtech, ramlib, std_cell_lib, synopsys"

Dim As Pair deps(33)
' Initialize deps array
deps(0) = Type<Pair>(2, 0)  : deps(1) = Type<Pair>(2, 14)
deps(2) = Type<Pair>(2, 13) : deps(3) = Type<Pair>(2, 4)
deps(4) = Type<Pair>(2, 3)  : deps(5) = Type<Pair>(2, 12)
deps(6) = Type<Pair>(2, 1)  : deps(7) = Type<Pair>(3, 1)
deps(8) = Type<Pair>(3, 10) : deps(9) = Type<Pair>(3, 11)
deps(10) = Type<Pair>(4, 1)  : deps(11) = Type<Pair>(4, 10)
deps(12) = Type<Pair>(5, 0)  : deps(13) = Type<Pair>(5, 14)
deps(14) = Type<Pair>(5, 10) : deps(15) = Type<Pair>(5, 4)
deps(16) = Type<Pair>(5, 3)  : deps(17) = Type<Pair>(5, 1)
deps(18) = Type<Pair>(5, 11) : deps(19) = Type<Pair>(6, 1)
deps(20) = Type<Pair>(6, 3)  : deps(21) = Type<Pair>(6, 10)
deps(22) = Type<Pair>(6, 11) : deps(23) = Type<Pair>(7, 1)
deps(24) = Type<Pair>(7, 10) : deps(25) = Type<Pair>(8, 1)
deps(26) = Type<Pair>(8, 10) : deps(27) = Type<Pair>(9, 1)
deps(28) = Type<Pair>(9, 10) : deps(29) = Type<Pair>(10, 1)
deps(30) = Type<Pair>(11, 1) : deps(31) = Type<Pair>(12, 0)
deps(32) = Type<Pair>(12, 1) : deps(33) = Type<Pair>(13, 1)

Dim As Graph g = Graph(s, deps())
Print "Topologically sorted order:"
Print g.topoSort()
Print

' Add new dependency
For i As Integer = 33 To 11 Step -1
    deps(i) = deps(i-1)
Next
deps(10) = Type<Pair>(3, 6)

Dim As Graph g2 = Graph(s, deps())
Print "Following the addition of dw04 to the dependencies of dw01:"
Print g2.topoSort()

Sleep