add day_03

day_03/1.rb

@@ -0,0 +1,19 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+class Main
+  def run
+    @sum = 0
+
+    $stdin.each_line do |line|
+      nums = line.chomp.each_char.map(&:to_i)
+      first_digit = nums[0..-2].sort.reverse[0]
+      second_digit = nums[nums.find_index(first_digit) + 1..].sort.reverse[0]
+      @sum += "#{first_digit}#{second_digit}".to_i
+    end
+
+    puts @sum
+  end
+end
+
+Main.new.run

day_03/2.rb

@@ -0,0 +1,27 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+class Main
+  def run
+    @sum = 0
+
+    $stdin.each_line do |line|
+      nums = line.chomp.each_char.map(&:to_i)
+      largest_joltage = recurse(12, nums, [])
+      @sum += largest_joltage.join.to_i
+    end
+
+    puts @sum
+  end
+
+  def recurse(i, nums, largest_joltage)
+    return largest_joltage if i == 0
+
+    max = nums[..-i].max
+    largest_joltage << max
+
+    recurse(i - 1, nums[nums.find_index(max) + 1..], largest_joltage)
+  end
+end
+
+Main.new.run