Merge other solutions into one file.

day1.cr

@@ -0,0 +1,20 @@
+changes = File.read("day1").split("\n")
+  .select { |it| !it.empty? } 
+  .map(&.to_i)
+
+puts "Final frequency: #{changes.sum}"
+
+count = { 0 => 1 }
+acc = 0
+
+changes.cycle do |i|
+  acc += i
+  old_count = count[acc]? || 0
+  new_count = old_count + 1
+  count[acc] = new_count
+
+  if new_count == 2
+    puts acc
+    exit
+  end
+end