use deletaged methods

use single instance of Grid

day_04/2.rb

@@ -15,15 +15,15 @@ class Main
     grid = Grid.new(data)
     loop do
       grid_updated = false
-      (0...grid.rows.size).each do |row_index|
+      (0...grid.size).each do |row_index|
-        (0...grid.columns.size).each do |column_index|
+        (0...grid[row_index].size).each do |column_index|
           cell = grid.cell_at(row_index, column_index)
           next unless cell.value == "@"
 
           if cell.neighbours.count do |neighbour|
             neighbour.value == "@"
           end < 4
-            data[row_index][column_index] = "x"
+            grid[row_index][column_index].value = "x"
             @sum += 1
             grid_updated = true
           end
@@ -31,7 +31,6 @@ class Main
       end
 
       break unless grid_updated
-      grid = Grid.new(data)
     end
 
     puts @sum