1 files changed, 50 insertions, 0 deletions
diff --git a/day3.rb b/day3.rb
new file mode 100755
index 0000000..17fd0ca
--- /dev/null
+++ b/day3.rb
@@ -0,0 +1,50 @@
+#!/usr/bin/env ruby
+
+map = {:onlysanta => Hash.new(0), :robosanta => Hash.new(0)}
+map[:onlysanta][[0,0]] += 1
+map[:robosanta][[0,0]] += 1
+
+onlysanta = {:northing => 0, :easting => 0}
+santa = {:northing => 0, :easting => 0}
+robosanta = {:northing => 0, :easting => 0}
+
+input = STDIN.readlines.map(&:chomp).join
+
+input.chars.each_with_index do |ch, idx|
+  case ch
+  when '<'
+    onlysanta[:easting] -= 1
+    if idx.odd? then
+      santa[:easting] -= 1
+    else
+      robosanta[:easting] -= 1
+    end
+  when '>'
+    onlysanta[:easting] += 1
+    if idx.odd? then
+      santa[:easting] += 1
+    else
+      robosanta[:easting] += 1
+    end
+  when 'v'
+    onlysanta[:northing] -= 1
+    if idx.odd? then
+      santa[:northing] -= 1
+    else
+      robosanta[:northing] -= 1
+    end
+  when '^'
+    onlysanta[:northing] += 1
+    if idx.odd? then
+      santa[:northing] += 1
+    else
+      robosanta[:northing] += 1
+    end
+  end
+  map[:onlysanta][[onlysanta[:easting], onlysanta[:northing]]] += 1
+  map[:robosanta][[santa[:easting], santa[:northing]]] += 1
+  map[:robosanta][[robosanta[:easting], robosanta[:northing]]] += 1
+end
+
+puts "Santa only: #{map[:onlysanta].length}"
+puts "Robosanta:  #{map[:robosanta].length}"