Solved special case using permutation

kata_potter.rb

@@ -13,19 +13,41 @@ def discount_applicable?(books)
   books.count == books.uniq.count && books.count >= MIN_BOOKS_FOR_DISCOUNT
 end
 
-def basket(books)
-  return calculate_discount_price(books.count) if discount_applicable?(books)
-  price_with_disccount = 0
+def basket_split(books, size)
 
-  if discount_applicable?(books.uniq)
-    price_with_disccount = calculate_discount_price(books.uniq.count) 
+  [books.first(size), books.last(books.count - size)]
+end
+
+def basket(books)
+  #return calculate_discount_price(books.count) if discount_applicable?(books)
 
-    books.uniq.each {|book| 
-      index_to_delete = books.index(book)
-      books.slice!(index_to_delete)
-    }
-    return price_with_disccount + books.count * BOOK_PRICE
+  #if discount_applicable?(books)
+   result = books.permutation.map{|element|
+      (0..element.length).map{|size|
+        partial_total = 0
+        basket_split(element, size).each{|books_splited|
+          if discount_applicable?(books_splited)
+            partial_total += calculate_discount_price(books_splited.count)
+          else 
+            partial_total += books_splited.count * BOOK_PRICE
+          end
+        }
+        #puts "partial_total= #{partial_total}"
+        partial_total          
+      }.min    
+    }.min
+    #puts "result=#{result}"
+    return result
+
+    #price_with_disccount = calculate_discount_price(books.uniq.count) 
+    #books.uniq.each {|book| 
+    #  index_to_delete = books.index(book)
+    #  books.slice!(index_to_delete)
+    #}
+    #return price_with_disccount + books.count * BOOK_PRICE 
+    #else
+    #  books.count * BOOK_PRICE 
+    #end
 
-  end
-  books.count * BOOK_PRICE
+
 end

test_potter.rb

@@ -41,5 +41,10 @@ def test_five_different_books_have_a_discount_25_percent
   def test_3_different_books_and_one_repeated_book
     assert_equal 29.6, basket([1,2,3,1])
   end
+
+  def test_2_different_books_and_3_repeated_book
+    assert_equal 51.20, basket([1,1,2,2,3,3,4,5])
+    #assert_equal 51.20, basket([1,2,3,4,1,2,3,5])
+  end
 
 end