Data commit

Task/One-dimensional-cellular-automata/Visual-Basic-.NET/one-dimensional-cellular-automata.vb

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+Imports System.Text
+
+Module CellularAutomata
+
+    Private Enum PetriStatus
+        Active
+        Stable
+        Dead
+    End Enum
+
+    Function Main(ByVal cmdArgs() As String) As Integer
+        If cmdArgs.Length = 0 Or cmdArgs.Length > 1 Then
+            Console.WriteLine("Command requires string of either 1s and 0s or #s and _s.")
+            Return 1
+        End If
+
+        Dim petriDish As BitArray
+
+        Try
+            petriDish = InitialisePetriDish(cmdArgs(0))
+        Catch ex As Exception
+            Console.WriteLine(ex.Message)
+            Return 1
+        End Try
+
+        Dim generation As Integer = 0
+        Dim ps As PetriStatus = PetriStatus.Active
+
+        Do While True
+            If ps = PetriStatus.Stable Then
+                Console.WriteLine("Sample stable after {0} generations.", generation - 1)
+                Exit Do
+            Else
+                Console.WriteLine("{0}: {1}", generation.ToString("D3"), BuildDishString(petriDish))
+                If ps = PetriStatus.Dead Then
+                    Console.WriteLine("Sample dead after {0} generations.", generation)
+                    Exit Do
+                End If
+            End If
+
+            ps = GetNextGeneration(petriDish)
+            generation += 1
+        Loop
+
+        Return 0
+    End Function
+
+    Private Function InitialisePetriDish(ByVal Sample As String) As BitArray
+        Dim PetriDish As New BitArray(Sample.Length)
+        Dim dead As Boolean = True
+
+        For i As Integer = 0 To Sample.Length - 1
+            Select Case Sample.Substring(i, 1)
+                Case "1", "#"
+                    PetriDish(i) = True
+                    dead = False
+                Case "0", "_"
+                    PetriDish(i) = False
+                Case Else
+                    Throw New Exception("Illegal value in string position " & i)
+                    Return Nothing
+            End Select
+        Next
+
+        If dead Then
+            Throw New Exception("Entered sample is dead.")
+            Return Nothing
+        End If
+
+        Return PetriDish
+    End Function
+
+    Private Function GetNextGeneration(ByRef PetriDish As BitArray) As PetriStatus
+        Dim petriCache = New BitArray(PetriDish.Length)
+        Dim neighbours As Integer
+        Dim stable As Boolean = True
+        Dim dead As Boolean = True
+
+        For i As Integer = 0 To PetriDish.Length - 1
+            neighbours = 0
+            If i > 0 AndAlso PetriDish(i - 1) Then neighbours += 1
+            If i < PetriDish.Length - 1 AndAlso PetriDish(i + 1) Then neighbours += 1
+
+            petriCache(i) = (PetriDish(i) And neighbours = 1) OrElse (Not PetriDish(i) And neighbours = 2)
+            If PetriDish(i) <> petriCache(i) Then stable = False
+            If petriCache(i) Then dead = False
+        Next
+
+        PetriDish = petriCache
+
+        If dead Then Return PetriStatus.Dead
+        If stable Then Return PetriStatus.Stable
+        Return PetriStatus.Active
+
+    End Function
+
+    Private Function BuildDishString(ByVal PetriDish As BitArray) As String
+        Dim sw As New StringBuilder()
+        For Each b As Boolean In PetriDish
+            sw.Append(IIf(b, "#", "_"))
+        Next
+
+        Return sw.ToString()
+    End Function
+End Module