1 files changed, 36 insertions, 0 deletions
diff --git a/day15/part1.rb b/day15/part1.rb
new file mode 100644
index 0000000..7dd3531
--- /dev/null
+++ b/day15/part1.rb
@@ -0,0 +1,36 @@
+class Sensor
+  def initialize(sx, sy, bx, by)
+    @x = sx
+    @y = sy
+    @range = (sx - bx).abs + (sy - by).abs
+  end
+
+  attr_reader :x, :y, :range
+end
+
+sensors = []
+beacons = []
+$stdin.readlines.each do |line|
+  c = line.scan(/x=(-?\d+), y=(-?\d+)/).flatten.map(&:to_i)
+  sensors << Sensor.new(*c)
+  beacons << c[2..3]
+end
+
+row = 2_000_000
+
+xranges = []
+sensors.each do |s|
+  dx = s.range - (s.y - row).abs
+  xranges << ((s.x - dx)..(s.x + dx)) if dx > 0
+end
+
+from = xranges.map(&:begin).min 
+to = xranges.map(&:end).max
+xs = to - from + 1
+
+(from..to).each do |x|
+  xs += 1 unless xranges.any? { |xrange| xrange.include?(x) }
+end
+xs -= beacons.select { |_, y| y == row }.map { |x, _| x }.uniq.count
+
+pp xs