diff --git a/2022/ruby/day_03.rb b/2022/ruby/day_03.rb
new file mode 100644
index 0000000..bea94f1
--- /dev/null
+++ b/2022/ruby/day_03.rb
@@ -0,0 +1,13 @@
+priorities = ((?a..?z).to_a + (?A..?Z).to_a).map.with_index { [_1, _2+1]  }.to_h
+
+# part 1
+# p ARGF.read.lines(chomp: true).map {|line|
+#   len = line.length
+#   a = line[0...len/2]
+#   b = line[len/2..]
+#   priorities.fetch((a.chars & b.chars)[0])
+# }.sum
+
+p ARGF.read.lines(chomp: true).each_slice(3).map {|chunk|
+  priorities.fetch(chunk.map(&:chars).inject(&:&)[0])
+}.sum