--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/day17.rb	Sun Dec 17 10:32:05 2023 +0000
@@ -0,0 +1,50 @@
+#! /usr/bin/env ruby
+
+if ARGV.length != 1
+        abort("Incorrect arguments - needs input file")
+elsif not File.exist? (ARGV[0])
+	abort("File #{ARGV[0]} did not exist")
+end
+
+file = ARGV[0]
+
+Coord = Struct.new(:x, :y)
+
+city_map = File.open(file, "r").each_line(chomp: true).map{ |line| line.each_char.map(&:to_i)}
+
+distances = Array.new(city_map.length) {Array.new(city_map[0].length) {Float::INFINITY}}
+distances[0][0] = 0
+
+visited = Array.new(city_map.length) {Array.new(city_map[0].length)}
+
+unvisited = []
+(0...city_map.length).each {|y| (0...city_map[0].length).each {|x| unvisited << Coord.new(x,y)}}
+
+def get_neighbours(city_map, x, y)
+	[Coord.new(-1,0), Coord.new(1,0), Coord.new(0,-1), Coord.new(0,1)].map {|coord| Coord.new(coord.x + x, coord.y + y)}.filter {|coord| coord.x >= 0 and coord.y >= 0 and coord.x < city_map[0].length and coord.y < city_map.length}
+end
+
+until unvisited.empty?
+	min_node = nil
+	unvisited.each do |node|
+		if min_node.nil? || distances[node.y][node.x] < distances[min_node.y][min_node.x]
+			min_node = node unless visited[node.y][node.x]
+		end
+	end
+
+	break if distances[min_node.y][min_node.x] == Float::INFINITY
+
+	cur_distance = distances[min_node.y][min_node.x]
+
+	get_neighbours(city_map, min_node.x, min_node.y).each do |neighbour|
+		value = city_map[neighbour.y][neighbour.x]
+		alt = cur_distance + value
+		distances[neighbour.y][neighbour.x] = alt if alt < distances[neighbour.y][neighbour.x]
+	end
+
+	visited[min_node.y][min_node.x] = true
+	unvisited.delete(min_node)
+	distances
+end
+
+puts distances[-1][-1]