Initial data commit

Task/Successive-prime-differences/Visual-Basic-.NET/successive-prime-differences.vb

@@ -0,0 +1,90 @@
+Imports System.Text
+
+Module Module1
+
+    Function Sieve(limit As Integer) As Integer()
+        Dim primes As New List(Of Integer) From {2}
+        Dim c(limit + 1) As Boolean REM composite = true
+        REM no need to process even numbers > 2
+        Dim p = 3
+        While True
+            Dim p2 = p * p
+            If p2 > limit Then
+                Exit While
+            End If
+            For i = p2 To limit Step 2 * p
+                c(i) = True
+            Next
+            Do
+                p += 2
+            Loop While c(p)
+        End While
+        For i = 3 To limit Step 2
+            If Not c(i) Then
+                primes.Add(i)
+            End If
+        Next
+        Return primes.ToArray
+    End Function
+
+    Function SuccessivePrimes(primes() As Integer, diffs() As Integer) As List(Of List(Of Integer))
+        Dim results As New List(Of List(Of Integer))
+        Dim dl = diffs.Length
+        Dim i = 0
+        While i < primes.Length - dl
+            Dim group(dl) As Integer
+            group(0) = primes(i)
+
+            Dim j = i
+            While j < i + dl
+                If primes(j + 1) - primes(j) <> diffs(j - i) Then
+                    GoTo outer REM continue the outermost loop
+                End If
+                group(j - i + 1) = primes(j + 1)
+
+                j += 1
+            End While
+            results.Add(group.ToList)
+outer:
+            i += 1
+        End While
+        Return results
+    End Function
+
+    Function CollectionToString(Of T)(c As IEnumerable(Of T)) As String
+        Dim builder As New StringBuilder
+        builder.Append("[")
+
+        Dim it = c.GetEnumerator()
+        If it.MoveNext() Then
+            builder.Append(it.Current)
+        End If
+        While it.MoveNext()
+            builder.Append(", ")
+            builder.Append(it.Current)
+        End While
+
+        builder.Append("]")
+        Return builder.ToString
+    End Function
+
+    Sub Main()
+        Dim primes = Sieve(999999)
+        Dim diffsList = {({2}), ({1}), ({2, 2}), ({2, 4}), ({4, 2}), ({6, 4, 2})}
+        Console.WriteLine("For primes less than 1,000,000:-")
+        Console.WriteLine()
+        For Each diffs In diffsList
+            Console.WriteLine("  For differences of {0} ->", CollectionToString(diffs))
+            Dim sp = SuccessivePrimes(primes, diffs)
+            If sp.Count = 0 Then
+                Console.WriteLine("    No groups found")
+                Continue For
+            End If
+            Console.WriteLine("    First group   = {0}", CollectionToString(sp(0)))
+            Console.WriteLine("    Last group    = {0}", CollectionToString(sp(sp.Count - 1)))
+            Console.WriteLine("    Number found  = {0}", sp.Count)
+            Console.WriteLine()
+        Next
+    End Sub
+
+End Module