day 18

Author: Peter de Kraker

day18_part1.rb

@@ -0,0 +1,29 @@
+def process(start, row_count)
+  rows = [start]
+  while (rows.length < row_count)
+    old_row = rows.last
+    new_row = [false] * old_row.length
+    new_row.each_with_index do |tile, i|
+      left,center,right = get_tiles(old_row, i)
+       trap = ((left && center && !right) || (center && right && !left) || (left && !center && !right) || (!left && !center && right))
+       new_row[i] = trap
+    end
+    rows << new_row
+  end
+  puts rows.flatten.count{|r| !r}
+end
+
+def get_tiles(old_row, i)
+  left = i > 0 ? old_row[i-1] : false
+  center = old_row[i]
+  right = (i < (old_row.length - 1)) ? old_row[i + 1] : false
+  [left,center,right]
+end
+
+input =".^^.^.^^^^"
+values = input.chars.map{|c|c =="^"}
+process(values, 10)
+
+ input = ".^^^^^.^^.^^^.^...^..^^.^.^..^^^^^^^^^^..^...^^.^..^^^^..^^^^...^.^.^^^^^^^^....^..^^^^^^.^^^.^^^.^^"
+ values = input.chars.map{|c|c =="^"}
+ process(values, 40)

day18_part2.rb

@@ -0,0 +1,30 @@
+def process(start, row_count)
+  rows = [start]
+  while (rows.length < row_count)
+    puts rows.length if rows.length % 100 == 0
+    old_row = rows.last
+    new_row = [false] * old_row.length
+    new_row.each_with_index do |tile, i|
+      left,center,right = get_tiles(old_row, i)
+       trap = ((left && center && !right) || (center && right && !left) || (left && !center && !right) || (!left && !center && right))
+       new_row[i] = trap
+    end
+    rows << new_row
+  end  
+  puts rows.flatten.count{|r| !r}
+end
+
+def get_tiles(old_row, i)
+  left = i > 0 ? old_row[i-1] : false
+  center = old_row[i]
+  right = (i < (old_row.length - 1)) ? old_row[i + 1] : false
+  [left,center,right]
+end
+
+input =".^^.^.^^^^"
+values = input.chars.map{|c|c =="^"}
+process(values, 10)
+
+ input = ".^^^^^.^^.^^^.^...^..^^.^.^..^^^^^^^^^^..^...^^.^..^^^^..^^^^...^.^.^^^^^^^^....^..^^^^^^.^^^.^^^.^^"
+ values = input.chars.map{|c|c =="^"}
+ process(values, 400000)