Add solutions for day 14.

day14.cr

@@ -0,0 +1,48 @@
+require "./common.cr"
+
+LINE_COUNT = 637061
+recipes = Deque(Int32).new
+recipes << 3
+recipes << 7
+elves = [0, 1]
+
+def add_recipes(recipes, elves)
+  new_num = elves.map { |it| recipes[it] }.sum
+  new_num.to_s.chars.map(&.to_i32).each do |n|
+    recipes << n
+  end
+
+  elves.each_with_index do |elf, index|
+    elves[index] = (elf + recipes[elf] + 1) % recipes.size
+  end
+end
+
+def index?(recipes, sequence, start_at = 0)
+  return nil if recipes.size < sequence.size
+  (recipes.size-sequence.size+1-start_at).times do |offset|
+    correct = true
+    sequence.each_with_index do |s, i|
+      correct &= (recipes[start_at + offset + i] == s)
+      break unless correct
+    end
+    return start_at + offset if correct
+  end
+  return nil
+end
+
+# Part 1
+while recipes.size < LINE_COUNT + 10
+  add_recipes(recipes, elves)
+end
+
+puts recipes.to_a[-10..-1].map(&.to_s).join
+
+# Part 2
+digits = LINE_COUNT.to_s.chars.map(&.to_i32)
+index = nil
+old_size = 0
+until (index = index?(recipes, digits, Math.max(old_size - 10, 0)))
+  old_size = recipes.size
+  add_recipes(recipes, elves)
+end
+puts index