[2019][ruby][10.x]

2019/ruby/day_10.rb

@@ -0,0 +1,32 @@
+require "pp"
+
+asteroids = ARGF.read.strip.lines.map(&:strip).map {|l| l.chars }
+
+max_y = asteroids.size
+max_x = asteroids.first.size
+
+asteroids = asteroids.flat_map.with_index {|row, y|
+  row.filter_map.with_index {|l, x| l == ?. ? nil : [x, y] }
+}
+
+asteroids = asteroids.each.with_object({}) {|(x, y), h|
+  visible = asteroids
+    .reject {|ax, ay| [x, y] == [ax, ay] }
+    .each.with_object(Hash.new {|h,k| h[k] = [] }) {|(ax, ay), ah|
+      rad = (Math.atan2(ax - x, y - ay) + 2*Math::PI) % (2*Math::PI)
+      ah[rad] << [ax, ay]
+    }
+
+  h[[x, y]] = visible
+}
+
+station = asteroids.max_by {|_,v| v.size }
+# p station.last.size
+
+asteroids = station.last.to_h.sort_by(&:first).map(&:last)
+199.times do
+  a = asteroids.shift
+  asteroids.concat(a[1..-1]) if a.first.is_a?(Array)
+end
+x, y = asteroids.first.first
+p 100*x + y