Day 18 part 1 Ruby solution

Author: creideiki

18-1.rb

@@ -0,0 +1,77 @@
+#!/usr/bin/env ruby
+
+require 'numo/narray'
+require 'algorithms'
+
+class Map
+  attr_accessor :map, :costs
+
+  def initialize
+    @height = 71
+    @width = 71
+    @map = Numo::UInt8.zeros(@height, @width)
+    @costs = Numo::UInt32.new(@height, @width).fill Numo::UInt32::MAX
+  end
+
+  def push!(input)
+    input.each do |line|
+      x, y = line.split(',').map(&:to_i)
+      @map[y, x] = 1
+    end
+  end
+
+  def solve!
+    queue = Containers::MinHeap.new
+    queue.push(0, { y: 0, x: 0 })
+
+    until queue.empty?
+      cost = queue.next_key
+      pos = queue.pop
+
+      y = pos[:y]
+      x = pos[:x]
+
+      @costs[y, x] = cost
+
+      return cost if y == @height - 1 && x == @width - 1
+
+      if y > 0 && @map[y - 1, x].zero? && @costs[y - 1, x] > (cost + 1) && @costs[y - 1, x] != Numo::UInt32::MAX - 1
+        queue.push(cost + 1, { y: y - 1, x: x })
+        @costs[y - 1, x] = Numo::UInt32::MAX - 1
+      end
+      if x < @width - 1 && @map[y, x + 1].zero? && @costs[y, x + 1] > (cost + 1) && @costs[y, x + 1] != Numo::UInt32::MAX - 1
+        queue.push(cost + 1, { y: y, x: x + 1 })
+        @costs[y, x + 1] = Numo::UInt32::MAX - 1
+      end
+      if y < @height - 1 && @map[y + 1, x].zero? && @costs[y + 1, x] > (cost + 1) && @costs[y + 1, x] != Numo::UInt32::MAX - 1
+        queue.push(cost + 1, { y: y + 1, x: x })
+        @costs[y + 1, x] = Numo::UInt32::MAX - 1
+      end
+      if x > 0 && @map[y, x - 1].zero? && @costs[y, x - 1] > (cost + 1) && @costs[y, x - 1] != Numo::UInt32::MAX - 1
+        queue.push(cost + 1, { y: y, x: x - 1 })
+        @costs[y, x - 1] = Numo::UInt32::MAX - 1
+      end
+    end
+  end
+
+  def inspect
+    to_s
+  end
+
+  def to_s
+    chars = ['.', '#']
+    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
+map.push! File.read('18.input').lines.map(&:strip)[..1023]
+puts map.solve!