Merge pull request #15 from pikesley/constrained-version

Better

Makefile

@@ -7,7 +7,10 @@ lint:
 	flake8 *py tests/
 
 install:
-	bundle
+	virtualenv .
+	. bin/activate
+	pip install -r requirements.txt
+	bundle install
 
 solve:
 	./towers console --discs $(or $(discs),3)

lib/ruby/constrained_towers.rb

@@ -1,17 +1,42 @@
 class ConstrainedTowers < Towers
-  @@directions = {}
-
   def initialize discs
     super
     @ternary = ConstrainedTowers.ternarise @count, @discs
+    @directions = {}
+    @stacks[0].each do |disc|
+      @directions[disc] = :right
+    end
   end
 
   def move
-    flip = Towers.diff ConstrainedTowers.ternarise(@count, @discs),
+    @flip = Towers.diff ConstrainedTowers.ternarise(@count, @discs),
                        ConstrainedTowers.ternarise(@count += 1, @discs)
-    source = Towers.find_disc flip, @stacks
+    @source = find_disc
+
+    @stacks[find_stack].push @stacks[@source].pop
+  end
 
-    @stacks[ConstrainedTowers.find_adjacent_stack flip, source, @stacks].push @stacks[source].pop
+  def find_disc
+    @stacks.each_with_index do |stack, index|
+      return index if stack.index @flip
+    end
+  end
+
+  def find_stack
+    case @source
+    when 0
+      @directions[@flip] = :right
+      return 1
+    when 2
+      @directions[@flip] = :left
+      return 1
+    when 1
+      if @directions[@flip] == :right
+        return 2
+      else
+        return 0
+      end
+    end
   end
 
   def binary
@@ -36,28 +61,4 @@ def inspect
   def ConstrainedTowers.ternarise value, width
     '%0*d' % [width, value.to_s(3)]
   end
-
-  def ConstrainedTowers.find_adjacent_stack disc, source, stacks
-    begin
-      direction = @@directions[disc]
-    rescue KeyError
-      @@directions[disc] = :right
-      direction = right
-    end
-
-    case source
-    when 0
-      @@directions[disc] = :right
-      return 1
-    when 2
-      @@directions[disc] = :left
-      return 1
-    when 1
-      if @@directions[disc] == :right
-        return 2
-      else
-        return 0
-      end
-    end
-  end
 end

spec/constrained_towers_spec.rb

@@ -12,27 +12,21 @@
       expect(Towers.diff '012', '020').to eq 1
     end
   end
-  context 'adjacent stacks' do
-    context 'noddy cases' do
-      it 'moves from left to centre' do
-        stacks = [[], [], []]
-        expect(ConstrainedTowers.find_adjacent_stack 0, 0, stacks).to eq 1
-      end
-
-      it 'moves from right to centre' do
-        stacks = [[], [], []]
-        expect(ConstrainedTowers.find_adjacent_stack 0, 2, stacks).to eq 1
-      end
-    end
-  end
 
-  it 'follows the rules' do
-    towers = ConstrainedTowers.new 4
+  context 'follow the rules' do
+    [2, 3, 4, 5, 6, 7, 8].each do |discs|
+      it "plays by the rules with %s discs" % discs do
+        towers = ConstrainedTowers.new discs
+        goal = towers.stacks[0].clone
+        until towers.solved do
+          towers.move
+          towers.stacks.each do |stack|
+            expect(stack.sort.reverse).to eq stack
+          end
+        end
 
-    until towers.solved do
-      towers.move
-      towers.stacks.each do |stack|
-        expect(stack.sort.reverse).to eq stack
+        expect(towers.stacks[2]).to eq goal
+        expect(towers.count).to eq (3 ** discs) - 1
       end
     end
   end