1 files changed, 43 insertions, 0 deletions
diff --git a/12/b.rb b/12/b.rb
new file mode 100644
index 0000000..4bd8ed0
--- /dev/null
+++ b/12/b.rb
@@ -0,0 +1,43 @@
+instructions = File.readlines('input.txt').map do |line|
+  [line.slice(0, 1), line.slice(1, line.length).to_i]
+end
+
+def rotate n, e, direction
+  case direction
+  when 0
+    [n, e]
+  when 90
+    [e, -n]
+  when 180
+    [-n, -e]
+  when 270
+    [-e, n]
+  end
+end
+
+ship_n = 0
+ship_e = 0
+waypoint_n = 1
+waypoint_e = 10
+
+instructions.each do |instruction|
+  case instruction[0]
+  when 'N'
+    waypoint_n += instruction[1]
+  when 'S'
+    waypoint_n -= instruction[1]
+  when 'E'
+    waypoint_e += instruction[1]
+  when 'W'
+    waypoint_e  -= instruction[1]
+  when 'F'
+    ship_n += waypoint_n * instruction[1]
+    ship_e += waypoint_e * instruction[1]
+  when 'L'
+    waypoint_n, waypoint_e = rotate waypoint_n, waypoint_e, instruction[1]
+  when 'R'
+    waypoint_n, waypoint_e = rotate waypoint_n, waypoint_e, (-instruction[1] % 360)
+  end
+end
+
+puts ship_n.abs + ship_e.abs