Add updated solutions, including day 20.

day17.cr

@@ -1,46 +1,47 @@
 require "advent"
+require "benchmark"
+
 INPUT = input(2020, 17).lines.map(&.chars) 
 
-def part1(input)
+def solve(input, dim)
   step = input.clone
-  cubes = Set({Int32,Int32,Int32,Int32}).new
-  new_cubes = Set({Int32,Int32,Int32,Int32}).new
+  cubes = Set(Array(Int32)).new
+  new_cubes = Set(Array(Int32)).new
   input.each_with_index do |row, y|
     row.each_with_index do |c, x|
-      cubes << {x,y,0,0} if c == '#'
+      cubes << [x,y].concat([0] * (dim-2)) if c == '#'
     end
   end
 
-  6.times do |i|
-    neighbor_count = {} of {Int32,Int32,Int32,Int32} => Int32
-    cubes.each do |c|
-      x,y,z,w = c
-      (-1..1).each do |dx|
-        (-1..1).each do |dy|
-          (-1..1).each do |dz|
-            (-1..1).each do |dw|
-              next if dx == 0 && dy == 0 && dz == 0 && dw == 0
-              neighbor_count[{x+dx,y+dy,z+dz,w+dw}] = (neighbor_count[{x+dx,y+dy,z+dz,w+dw}]? || 0) + 1
-            end
-          end
-        end
+  8.times do |i|
+    print '.'
+    neighbor_count = Hash(Array(Int32), Int32).new(0)
+    Array.product([[-1,0,1]] * dim).each do |diff|
+      next if diff.all? &.==(0)
+      cubes.each do |c|
+        neighbor_count[c.zip_with(diff) { |a,b| a+b }] += 1
       end
     end
+
     new_cubes.clear
     neighbor_count.each do |n, i|
-      if cubes.includes?(n)
-        new_cubes << n if (i == 2 || i == 3)
-      elsif i == 3
-        new_cubes << n
-      end
+      new_cubes << n if i == 3 || (cubes.includes?(n) && i == 2)
     end
     new_cubes, cubes = cubes, new_cubes
   end
   cubes.size
 end
 
-def part2(input)
+def part1(input)
+  solve(input, 3)
 end
 
-puts part1(INPUT.clone)
-puts part2(INPUT.clone)
+def part2(input)
+  solve(input, 4)
+end
+
+(3..).each do |i|
+  print "Dim #{i} "
+  bm = Benchmark.measure { puts " #{solve(INPUT, i)}" }
+  puts bm.real * 1000
+end