Add solution for 2015 day 02

2015/README.md

@@ -2,7 +2,7 @@
 
 ## Progress
 - [x] Day 01
-- [ ] Day 02
+- [x] Day 02
 - [ ] Day 03
 - [ ] Day 04
 - [ ] Day 05

2015/day-02/inputs/test.txt

@@ -0,0 +1,2 @@
+2x3x4
+1x1x10

2015/day-02/main.rb

@@ -0,0 +1,55 @@
+#!/usr/bin/env ruby
+
+require "pathname"
+
+INPUTS = [
+  Pathname("inputs/test.txt"),
+  Pathname("inputs/puzzle.txt"),
+].freeze
+
+def parse_input(data)
+  data.chomp.split("x").map(&:to_i)
+end
+
+def sides(length, width, height)
+  [length * width, width * height, height * length]
+end
+
+def solve_part_1(input)
+  input.lines.sum do |line|
+    sides = sides(*parse_input(line))
+    smallest = sides.min
+    sides.sum { |x| x * 2 } + smallest
+  end
+end
+
+def solve_part_2(input)
+  input.lines.sum do |line|
+    length, width, height = parse_input(line)
+    sides = sides(length, width, height)
+    circumference =
+      case sides.map.with_index.min.last
+      when 0 then length * 2 + width * 2
+      when 1 then width * 2 + height * 2
+      when 2 then height * 2 + length * 2
+      end
+    circumference + length * width * height
+  end
+end
+
+def main(files)
+  files.each do |file|
+    puts "File: #{file}"
+    content = file.read
+
+    result = solve_part_1(content.chomp)
+    puts "  Wrapping Paper: #{result}"
+    puts " -" * 15
+
+    result = solve_part_2(content.chomp)
+    puts "  Ribbon Length: #{result}"
+    puts " -" * 15
+  end
+end
+
+main(INPUTS)