Data commit

Task/Pentomino-tiling/Visual-Basic-.NET/pentomino-tiling.vb

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+Module Module1
+
+    Dim symbols As Char() = "XYPFTVNLUZWI█".ToCharArray(),
+        nRows As Integer = 8, nCols As Integer = 8,
+        target As Integer = 12, blank As Integer = 12,
+        grid As Integer()() = New Integer(nRows - 1)() {},
+        placed As Boolean() = New Boolean(target - 1) {},
+        pens As List(Of List(Of Integer())), rand As Random,
+        seeds As Integer() = {291, 292, 293, 295, 297, 329, 330, 332, 333, 335, 378, 586}
+
+    Sub Main()
+        Unpack(seeds) : rand = New Random() : ShuffleShapes(2)
+        For r As Integer = 0 To nRows - 1
+            grid(r) = Enumerable.Repeat(-1, nCols).ToArray() : Next
+        For i As Integer = 0 To 3
+            Dim rRow, rCol As Integer : Do : rRow = rand.Next(nRows) : rCol = rand.Next(nCols)
+            Loop While grid(rRow)(rCol) = blank : grid(rRow)(rCol) = blank
+        Next
+        If Solve(0, 0) Then
+            PrintResult()
+        Else
+            Console.WriteLine("no solution for this configuration:") : PrintResult()
+        End If
+        If System.Diagnostics.Debugger.IsAttached Then Console.ReadKey()
+    End Sub
+
+    Sub ShuffleShapes(count As Integer) ' changes order of the pieces for a more random solution
+        For i As Integer = 0 To count : For j = 0 To pens.Count - 1
+                Dim r As Integer : Do : r = rand.Next(pens.Count) : Loop Until r <> j
+                Dim tmp As List(Of Integer()) = pens(r) : pens(r) = pens(j) : pens(j) = tmp
+                Dim ch As Char = symbols(r) : symbols(r) = symbols(j) : symbols(j) = ch
+            Next : Next
+    End Sub
+
+    Sub PrintResult() ' display results
+        For Each r As Integer() In grid : For Each i As Integer In r
+                Console.Write("{0} ", If(i < 0, ".", symbols(i)))
+            Next : Console.WriteLine() : Next
+    End Sub
+
+    ' returns first found solution only
+    Function Solve(ByVal pos As Integer, ByVal numPlaced As Integer) As Boolean
+        If numPlaced = target Then Return True
+        Dim row As Integer = pos \ nCols, col As Integer = pos Mod nCols
+        If grid(row)(col) <> -1 Then Return Solve(pos + 1, numPlaced)
+        For i As Integer = 0 To pens.Count - 1 : If Not placed(i) Then
+                For Each orientation As Integer() In pens(i)
+                    If Not TPO(orientation, row, col, i) Then Continue For
+                    placed(i) = True : If Solve(pos + 1, numPlaced + 1) Then Return True
+                    RmvO(orientation, row, col) : placed(i) = False
+                Next : End If : Next : Return False
+    End Function
+
+    ' removes a placed orientation
+    Sub RmvO(ByVal ori As Integer(), ByVal row As Integer, ByVal col As Integer)
+        grid(row)(col) = -1 : For i As Integer = 0 To ori.Length - 1 Step 2
+            grid(row + ori(i))(col + ori(i + 1)) = -1 : Next
+    End Sub
+
+    ' checks an orientation, if possible it is placed, else returns false
+    Function TPO(ByVal ori As Integer(), ByVal row As Integer, ByVal col As Integer,
+                 ByVal sIdx As Integer) As Boolean
+        For i As Integer = 0 To ori.Length - 1 Step 2
+            Dim x As Integer = col + ori(i + 1), y As Integer = row + ori(i)
+            If x < 0 OrElse x >= nCols OrElse y < 0 OrElse y >= nRows OrElse
+                grid(y)(x) <> -1 Then Return False
+        Next : grid(row)(col) = sIdx
+        For i As Integer = 0 To ori.Length - 1 Step 2
+            grid(row + ori(i))(col + ori(i + 1)) = sIdx
+        Next : Return True
+    End Function
+
+    '!' the following routines expand the seed values into the 63 orientation arrays.
+    '   source code space savings comparison:
+    '      around 2000 chars for the expansion code, verses about 3000 chars for the integer array defs.
+    '   perhaps not worth the savings?
+
+    Sub Unpack(sv As Integer()) ' unpacks a list of seed values into a set of 63 rotated pentominoes
+        pens = New List(Of List(Of Integer())) : For Each item In sv
+            Dim Gen As New List(Of Integer()), exi As List(Of Integer) = Expand(item),
+                fx As Integer() = ToP(exi) : Gen.Add(fx) : For i As Integer = 1 To 7
+                If i = 4 Then Mir(exi) Else Rot(exi)
+                fx = ToP(exi) : If Not Gen.Exists(Function(Red) TheSame(Red, fx)) Then Gen.Add(ToP(exi))
+            Next : pens.Add(Gen) : Next
+    End Sub
+
+    ' expands an integer into a set of directions
+    Function Expand(i As Integer) As List(Of Integer)
+        Expand = {0}.ToList() : For j As Integer = 0 To 3 : Expand.Insert(1, i And 15) : i >>= 4 : Next
+    End Function
+
+    ' converts a set of directions to an array of y, x pairs
+    Function ToP(p As List(Of Integer)) As Integer()
+        Dim tmp As List(Of Integer) = {0}.ToList() : For Each item As Integer In p.Skip(1)
+            tmp.Add(tmp.Item(item >> 2) + {1, 8, -1, -8}(item And 3)) : Next
+        tmp.Sort() : For i As Integer = tmp.Count - 1 To 0 Step -1 : tmp.Item(i) -= tmp.Item(0) : Next
+        Dim res As New List(Of Integer) : For Each item In tmp.Skip(1)
+            Dim adj = If((item And 7) > 4, 8, 0)
+            res.Add((adj + item) \ 8) : res.Add((item And 7) - adj)
+        Next : Return res.ToArray()
+    End Function
+
+    ' compares integer arrays for equivalency
+    Function TheSame(a As Integer(), b As Integer()) As Boolean
+        For i As Integer = 0 To a.Count - 1 : If a(i) <> b(i) Then Return False
+        Next : Return True
+    End Function
+
+    Sub Rot(ByRef p As List(Of Integer)) ' rotates a set of directions by 90 degrees
+        For i As Integer = 0 To p.Count - 1 : p(i) = (p(i) And -4) Or ((p(i) + 1) And 3) : Next
+    End Sub
+
+    Sub Mir(ByRef p As List(Of Integer)) ' mirrors a set of directions
+        For i As Integer = 0 To p.Count - 1 : p(i) = (p(i) And -4) Or (((p(i) Xor 1) + 1) And 3) : Next
+    End Sub
+
+End Module