diff --git a/2018/ruby/day_06.rb b/2018/ruby/day_06.rb
new file mode 100644
index 0000000..1467ade
--- /dev/null
+++ b/2018/ruby/day_06.rb
@@ -0,0 +1,45 @@
+require "set"
+
+coords = ARGF.read.chomp.lines.map(&:chomp).map {|line| line.split(", ").map(&:to_i) }
+
+x_min = coords.map(&:first).min
+x_max = coords.map(&:first).max
+y_min = coords.map(&:last).min
+y_max = coords.map(&:last).max
+
+coords = coords.map.with_index {|c,i| [i, c] }
+
+p coords
+
+p x_min, x_max, y_min, y_max
+
+def manhattan_distance(a, b)
+  (a[0] - b[0]).abs + (a[1] - b[1]).abs
+end
+
+grid = {}
+(x_min..x_max).each do |x|
+  (y_min..y_max).each do |y|
+    distances = coords.map {|id, coord|
+      [id, manhattan_distance(coord, [x,y])]
+    }
+    min_distance = distances.map(&:last).min
+    closests = distances.select {|_,distance| distance == min_distance }
+    grid[[x,y]] = closests.length > 1 ? nil : closests.first.first
+  end
+end
+
+infinites = Set.new
+(x_min..x_max).each do |x|
+  infinites << grid[[x,y_min]]
+  infinites << grid[[x,y_max]]
+end
+(y_min..y_max).each do |y|
+  infinites << grid[[x_min,y]]
+  infinites << grid[[x_max,y]]
+end
+
+p grid
+
+p infinites
+p grid.values.group_by(&:itself).transform_values(&:count).reject {|k,_| infinites.include?(k) }.max_by(&:last)