Day 16 part 1 Ruby solution

Author: creideiki

16-1.rb

@@ -0,0 +1,89 @@
+#!/usr/bin/env ruby
+
+require 'numo/narray'
+require 'algorithms'
+
+class Map
+  attr_accessor :map
+
+  def initialize(input)
+    @height = input.size
+    @width = input[0].size
+    @map = Numo::UInt8.zeros(@height, @width)
+    @costs = Numo::UInt32.new(@height, @width).fill Numo::UInt32::MAX
+
+    @height.times do |y|
+      @width.times do |x|
+        case input[y][x]
+        when '.'
+          @map[y, x] = 0
+        when '#'
+          @map[y, x] = 1
+        when 'S'
+          @map[y, x] = 2
+          @start = { y: y, x: x }
+        when 'E'
+          @map[y, x] = 3
+          @end = { y: y, x: x }
+        end
+      end
+    end
+  end
+
+  def solve!
+    queue = Containers::MinHeap.new
+    queue.push(0, { y: @start[:y], x: @start[:x], dir: :east })
+
+    until queue.empty?
+      cost = queue.next_key
+      pos = queue.pop
+
+      y = pos[:y]
+      x = pos[:x]
+      dir = pos[:dir]
+
+      @costs[y, x] = cost if cost < @costs[y, x]
+
+      return cost if y == @end[:y] && x == @end[:x]
+
+      case dir
+      when :north
+        queue.push(cost + 1, { y: y - 1, x: x, dir: :north }) if @map[y - 1, x] != 1 && @costs[y - 1, x] > cost + 1
+        queue.push(cost + 1000, { y: y, x: x, dir: :east }) if @map[y, x + 1] != 1 && @costs[y, x + 1] > cost + 1000
+        queue.push(cost + 1000, { y: y, x: x, dir: :west }) if @map[y, x - 1] != 1 && @costs[y, x - 1] > cost + 1000
+      when :east
+        queue.push(cost + 1, { y: y, x: x + 1, dir: :east }) if @map[y, x + 1] != 1 && @costs[y, x + 1] > cost + 1
+        queue.push(cost + 1000, { y: y, x: x, dir: :south }) if @map[y + 1, x] != 1 && @costs[y + 1, x] > cost + 1000
+        queue.push(cost + 1000, { y: y, x: x, dir: :north }) if @map[y - 1, x] != 1 && @costs[y - 1, x] > cost + 1000
+      when :south
+        queue.push(cost + 1, { y: y + 1, x: x, dir: :south }) if @map[y + 1, x] != 1 && @costs[y + 1, x] > cost + 1
+        queue.push(cost + 1000, { y: y, x: x, dir: :west }) if @map[y, x - 1] != 1 && @costs[y, x - 1] > cost + 1000
+        queue.push(cost + 1000, { y: y, x: x, dir: :east }) if @map[y, x + 1] != 1 && @costs[y, x + 1] > cost + 1000
+      when :west
+        queue.push(cost + 1, { y: y, x: x - 1, dir: :west }) if @map[y, x - 1] != 1 && @costs[y, x - 1] > cost + 1
+        queue.push(cost + 1000, { y: y, x: x, dir: :north }) if @map[y - 1, x] != 1 && @costs[y - 1, x] > cost + 1000
+        queue.push(cost + 1000, { y: y, x: x, dir: :south }) if @map[y + 1, x] != 1 && @costs[y + 1, x] > cost + 1000
+      end
+    end
+  end
+
+  def inspect
+    to_s
+  end
+
+  def to_s
+    chars = ['.', '#', 'S', 'E']
+    s = "<#{self.class}:\n"
+    @height.times do |y|
+      @width.times do |x|
+        s += chars[@map[y, x]]
+      end
+      s += "\n"
+    end
+    s += '>'
+    s
+  end
+end
+
+map = Map.new File.read('16.input').lines.map(&:strip)
+puts map.solve!