1 files changed, 59 insertions, 0 deletions
diff --git a/day17/part2.rb b/day17/part2.rb
new file mode 100644
index 0000000..da6280b
--- /dev/null
+++ b/day17/part2.rb
@@ -0,0 +1,59 @@
+jets = $stdin.read.strip.chars
+jetp = 0
+njets = jets.count
+
+rocks = [
+  [ 1|2|4|8              ],
+  [ 2,       1|2|4, 2    ],
+  [ 1|2|4,   4,     4    ],
+  [ 1,       1,     1, 1 ],
+  [ 1|2,     1|2         ]
+]
+rockp = 0
+nrocks = rocks.count
+
+def rock_blocked(atx, aty, chamber, rock)
+  return true if atx < 0 || aty < 0
+
+  return true if rock.map{|row|row << atx}.any?{|row|row > 127}
+
+  rock.each_with_index do |rxs, ry|
+    next if chamber[aty + ry].nil?
+    return true if (chamber[aty + ry] & (rxs << atx)) != 0
+  end
+
+  return false
+end
+
+chamber = []
+
+1000000000000.times do
+  atx = 2
+  aty = chamber.count + 3
+
+  rock = rocks[rockp]
+  rockp = (rockp + 1) % nrocks
+
+  loop do
+    case jets[jetp]
+    when ?<
+      atx -= 1 unless rock_blocked(atx - 1, aty, chamber, rock)
+    when ?>
+      atx += 1 unless rock_blocked(atx + 1, aty, chamber, rock)
+    end
+    jetp = (jetp + 1) % njets
+
+    if rock_blocked(atx, aty - 1, chamber, rock)
+      rock.each_with_index do |rxs, ry|
+        sy = aty + ry
+        chamber[sy] = 0 if chamber[sy].nil?
+        chamber[sy] |= (rxs << atx)
+      end
+      break
+    else
+      aty -= 1
+    end
+  end
+end
+
+puts chamber.count