More minitest

ruby/2015/2/bin/problem

@@ -0,0 +1,7 @@
+#/usr/bin/env ruby
+
+require "present"
+lines = STDIN.read.chomp.split("\n")
+presents = lines.map { |line| Present.for line }
+puts "Part 1: #{presents.map(&:paper).sum}"
+puts "Part 2: #{presents.map(&:ribbon).sum}"

ruby/2015/2/lib/present.rb

@@ -0,0 +1,41 @@
+class Present
+  attr_reader :l, :w, :h
+
+  def initialize(l, w, h)
+    @l = l
+    @w = w
+    @h = h
+  end
+
+  def self.for(string)
+    new *string.split("x").map(&:to_i)
+  end
+
+  def paper
+    surface_area + slack
+  end
+
+  def side_areas
+    [l*w, l*h, w*h]
+  end
+
+  def surface_area
+    side_areas.sum * 2
+  end
+
+  def slack
+    side_areas.min
+  end
+
+  def perimeters
+    [2*(l+w), 2*(l+h), 2*(w+h)]
+  end
+
+  def volume
+    l*w*h
+  end
+
+  def ribbon
+    perimeters.min + volume
+  end
+end

ruby/2015/2/test/test_present.rb

@@ -0,0 +1,14 @@
+require "minitest/autorun"
+require "present"
+
+class TestPresent < Minitest::Test
+  def test_paper
+    assert_equal(58, Present.for("2x3x4").paper)
+    assert_equal(43, Present.for("1x1x10").paper)
+  end
+
+  def test_ribbon
+    assert_equal(34, Present.for("2x3x4").ribbon)
+    assert_equal(14, Present.for("1x1x10").ribbon)
+  end
+end