1 files changed, 29 insertions, 0 deletions
diff --git a/day18/part1.rb b/day18/part1.rb
new file mode 100644
index 0000000..dd4ba41
--- /dev/null
+++ b/day18/part1.rb
@@ -0,0 +1,29 @@
+require 'set'
+
+grid = Hash.new
+
+$stdin.readlines.each do |line|
+  x, y, z = line.strip.split(?,).map(&:to_i)
+  grid[x] = Hash.new if grid[x].nil?
+  grid[x][y] = Set.new if grid[x][y].nil?
+  grid[x][y] << z
+end
+
+sa = 0
+
+grid.each do |x, yzs|
+  yzs.each do |y, zs|
+    zs.each do |z|
+      tsa = 6
+      tsa -= 1 if !grid[x-1].nil? && grid[x-1][y]&.include?(z)
+      tsa -= 1 if !grid[x+1].nil? && grid[x+1][y]&.include?(z)
+      tsa -= 1 if grid[x][y-1]&.include?(z)
+      tsa -= 1 if grid[x][y+1]&.include?(z)
+      tsa -= 1 if grid[x][y].include?(z-1)
+      tsa -= 1 if grid[x][y].include?(z+1)
+      sa += tsa
+    end
+  end
+end
+
+puts sa