Split day 12 puzzles

Author: ariejan

lib/solutions/day_12.rb

@@ -1,5 +1,15 @@
 class Day12
   def part_one(input)
+    Day12Part1.new.part_one(input)
+  end
+
+  def part_two(input)
+    Day12Part2.new.part_two(input)
+  end
+end
+
+class Day12Part2
+  def part_two(input)
     @map = input.split("\n")
     @rows = @map.length
     @cols = @map[0].length
@@ -8,8 +18,67 @@ def part_one(input)
     total_price
   end
 
-  def part_two(input)
-    0
+  def total_price
+    regions = find_regions
+    regions.sum { |region| region[:area] * region[:perimeter] }
+  end
+
+  def find_regions
+    regions = []
+    (0...@rows).each do |row|
+      (0...@cols).each do |col|
+        next if @visited[row][col]
+
+        char = @map[row][col]
+        area, perimeter = explore_region(row, col, char)
+        regions << { area: area, perimeter: perimeter }
+      end
+    end
+    regions
+  end
+
+  def explore_region(row, col, char)
+    queue = [[row, col]]
+    area = 0
+    perimeter = 0
+
+    until queue.empty?
+      current_row, current_col = queue.shift
+      next if out_of_bounds?(current_row, current_col) || @visited[current_row][current_col]
+
+      next unless @map[current_row][current_col] == char
+
+      @visited[current_row][current_col] = true
+      area += 1
+
+      # Check all four directions
+      [[0, 1], [1, 0], [0, -1], [-1, 0]].each do |dr, dc|
+        new_row = current_row + dr
+        new_col = current_col + dc
+        if out_of_bounds?(new_row, new_col) || @map[new_row][new_col] != char
+          perimeter += 1
+        else
+          queue << [new_row, new_col] unless @visited[new_row][new_col]
+        end
+      end
+    end
+
+    [area, perimeter]
+  end
+
+  def out_of_bounds?(row, col)
+    row < 0 || row >= @rows || col < 0 || col >= @cols
+  end
+end
+
+class Day12Part1
+  def part_one(input)
+    @map = input.split("\n")
+    @rows = @map.length
+    @cols = @map[0].length
+    @visited = Array.new(@rows) { Array.new(@cols, false) }
+
+    total_price
   end
 
   def total_price