day 12 part b

Author: schoblaska

12/a.rb

@@ -12,6 +12,8 @@
   cxy = nodes.select { |k, v| !v[:visited] }.min_by { |k, v| v[:dist] }[0]
   cv = grid[*cxy]
 
+  p nodes[cxy][:dist] and break if cv == "E"
+
   grid.each_neighbor(*cxy, diags: false) do |nxy, nv|
     nodes[nxy] ||= { visited: false, dist: Float::INFINITY }
 
@@ -21,8 +23,4 @@
   end
 
   nodes[cxy][:visited] = true
-
-  break if grid[*cxy] == "E"
 end
-
-p nodes[grid.index("E")][:dist]

12/b.rb

@@ -0,0 +1,26 @@
+require "set"
+require_relative "../lib/grid"
+
+grid = Grid.from_file("12/input.txt")
+nodes = { grid.index("E") => { visited: false, dist: 0 } }
+heights =
+  { "S" => 0, "E" => 25 }.tap do |h|
+    ("a".."z").each_with_index { |v, i| h[v] = i }
+  end
+
+loop do
+  cxy = nodes.select { |k, v| !v[:visited] }.min_by { |k, v| v[:dist] }[0]
+  cv = grid[*cxy]
+
+  p nodes[cxy][:dist] and break if cv == "a"
+
+  grid.each_neighbor(*cxy, diags: false) do |nxy, nv|
+    nodes[nxy] ||= { visited: false, dist: Float::INFINITY }
+
+    if heights[cv] - heights[nv] <= 1
+      nodes[nxy][:dist] = [nodes[nxy][:dist], nodes[cxy][:dist] + 1].min
+    end
+  end
+
+  nodes[cxy][:visited] = true
+end