Day 10

days/day10.rb

@@ -0,0 +1,132 @@
+require_relative '../lib/aoc'
+require_relative '../lib/grid'
+
+module Day10
+	extend AOC::Day
+
+	@num = 10
+	@ans_test1 = 8
+	@ans_test2 = 10
+
+	CONNECTS = {
+		[1, 0]  => ["-", "7", "J"],
+		[0, 1]  => ["|", "L", "J"],
+		[-1, 0] => ["-", "L", "F"],
+		[0, -1] => ["|", "7", "F"],
+	}
+
+	NEIGHBORS = {
+		"|" => [[0, -1], [0, 1]],
+		"-" => [[-1, 0], [1, 0]],
+		"L" => [[0, -1], [1, 0]],
+		"J" => [[0, -1], [-1, 0]],
+		"7" => [[-1, 0], [0, 1]],
+		"F" => [[1, 0], [0, 1]],
+	}
+
+	def self.solve_part1(input)
+		grid = Grid.string_to_grid(input)
+
+		s_x, s_y = find_and_replace_start(grid)
+		visited = find_loop(grid, s_x, s_y)
+
+		return visited.values.max
+	end
+
+	def self.solve_part2(input)
+		grid = Grid.string_to_grid(input)
+		s_x, s_y = find_and_replace_start(grid)
+		visited = find_loop(grid, s_x, s_y)
+
+		r = 0
+		grid.each_with_index do |row, y|
+			in_loop = false
+			last_corner = nil
+			row.split("").each_with_index do |c, x|
+				if visited.key?([x, y])
+					# This coord is part of the loop
+					if c == "|" or (c == "J" and last_corner == "F") or (c == "7" and last_corner == "L")
+						in_loop = !in_loop
+					end
+
+					last_corner = c if ["7", "J", "L", "F"].include?(c)
+				else
+					# Not part of the loop
+					r += 1 if in_loop
+				end
+			end
+		end
+
+		return r
+	end
+
+	def self.find_loop(grid, s_x, s_y)
+		to_visit = {}
+		visited = {}
+		to_visit[[s_x, s_y]] = 0
+		while to_visit.length > 0
+			coords, cost = to_visit.shift
+			x, y = coords
+			visited[[x, y]] = cost
+
+			NEIGHBORS[grid[y][x]].each do |dx, dy|
+				nx = x+dx
+				ny = y+dy
+				nc = cost+1
+
+				next if visited.key?([nx, ny])
+
+				if to_visit.key?([nx, ny])
+					if to_visit[[nx, ny]] > nc
+						to_visit[[nx, ny]] = nc
+					end
+				else
+					to_visit[[nx, ny]] = nc
+				end
+			end
+		end
+
+		return visited
+	end
+
+	def self.find_and_replace_start(grid)
+		s_x = s_y = -1
+		grid.each_with_index do |line, y|
+			line.split("").each_with_index do |char, x|
+				if char == "S"
+					s_x = x
+					s_y = y
+					break
+				end
+			end
+			break if s_x != -1
+		end
+
+		s = find_start_symbol(grid, s_x, s_y)
+		grid[s_y].sub!("S", s)
+
+		return [s_x, s_y]
+	end
+
+	def self.find_start_symbol(grid, s_x, s_y)
+		r = ""
+		[[1, 0], [0, 1], [-1, 0], [0, -1]].each do |dx, dy|
+			nx = s_x+dx
+			ny = s_y+dy
+			next unless CONNECTS[[dx, dy]].include?(grid[ny][nx])
+			r += dx.to_s + dy.to_s
+		end
+
+		translate = {
+			"10-10" => "-",
+			"100-1" => "L",
+			"1001" => "F",
+			"010-1" => "|",
+			"01-10" => "7",
+			"-100-1" => "J"
+		}
+		return translate[r]
+	end
+end
+
+Day10.run

inputs/test/test_input10_p1

@@ -0,0 +1,5 @@
+7-F7-
+.FJ|7
+SJLL7
+|F--J
+LJ.LJ

inputs/test/test_input10_p2

@@ -0,0 +1,10 @@
+FF7FSF7F7F7F7F7F---7
+L|LJ||||||||||||F--J
+FL-7LJLJ||||||LJL-77
+F--JF--7||LJLJ7F7FJ-
+L---JF-JLJ.||-FJLJJ7
+|F|F-JF---7F7-L7L|7|
+|FFJF7L7F-JF7|JL---7
+7-L-JL7||F7|L7F-7F7|
+L.L7LFJ|||||FJL7||LJ
+L7JLJL-JLJLJL--JLJ.L

lib/grid.rb

@@ -1,6 +1,6 @@
 module Grid
 	def self.string_to_grid(inp)
-		return inp.lines.map{ |line| line.strip.split("") }
+		return inp.lines.map{ |line| line.strip }
 	end
 
 	def self.get_neighbours(grid, x, y, include_coords = false)