1 files changed, 48 insertions, 0 deletions
diff --git a/day20.rb b/day20.rb
new file mode 100644
index 0000000..1b4fc78
--- /dev/null
+++ b/day20.rb
@@ -0,0 +1,48 @@
+r = File.read("day20")
+
+#r = "^ENNWSWW(NEWS|)SSSEEN(WNSE|)EE(SWEN|)NNN$"
+#r = "^WSSEESWWWNW(S|NENNEEEENN(ESSSSW(NWSW|SSEN)|WSWWN(E|WWS(E|SS))))$"
+
+r.gsub!(/^\^|\$$/, '')
+
+
+def dist(str)
+  seen = []
+  x = y = 0
+  str.chars.each { |c|
+    case c
+    when "E"; x += 1
+    when "W"; x -= 1
+    when "S"; y += 1
+    when "N"; y -= 1
+    end
+    seen << [x,y]
+  }
+  seen.uniq.size
+end
+
+p1 = 0
+p2 = 0
+
+stk = [""]
+r.chars.each { |c|
+  case c
+  when "E", "S", "W", "N"
+    stk.last << c
+    p1 = [p1, dist(stk.last)].max
+    p2 += 1  if dist(stk.last) > 1000
+  when "("
+    stk << stk.last.dup
+  when "|"
+    stk.pop
+    stk << stk.last.dup
+  when ")"
+    stk.pop
+  end
+}
+
+p p1  # 3788
+p p2  # 8568
+
+# 9558 too high
+# 9557 too high