Reduce large maze to single width corridors This reduces the permutations for a x x x b x To one (two steps north) from four (two steps north; one east, two north, one west; one east, one north, one west, one north; and one north, one east, one north, one west). Longer corridors were worse! We would filter this in the "been here before via another path" but that's still a lot of lookups in lists, which is inefficient.

day2.txt
  File contents go here
day2.txt
  File contents go here
  Extra content here
day2.txt
  Non-block file content
{"a"=>"one", "b"=>"two", "c"=>"three"}
[["a", "one"], ["b", "two"], ["c", "three"]]
["a", "b", "c"]
["one", "two", "three"]
["one", "two", "three"]
{0=>"one", 1=>"two", 2=>"three"}