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advent-of-code/2016/ruby/day_13.rb

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class Maze
attr_reader :walls
def initialize(seed)
@walls = Hash.new {|h,(x,y)|
num = x*x + 3*x + 2*x*y + y + y*y + seed
h[[x,y]] = num.to_s(2).chars.count {|c| c == ?1 }.odd?
}
end
def [](x,y)
walls[[x, y]]
end
def solve(from, to)
seen = Set.new
current = [[from, 0]]
loop do
pos, count = current.shift
seen << pos
x,y = pos
[[1,0], [-1,0], [0,1], [0,-1]].map {|dx, dy|
[x + dx, y + dy]
}.reject {|x,y|
x.negative? || y.negative?
}.reject {|x,y|
walls[[x,y]]
}.reject {|x,y|
seen.include?([x,y])
}.each do |x,y|
return count + 1 if to == [x,y]
current << [[x,y], count + 1]
end
end
end
end
if __FILE__ == $0
maze = Maze.new(1358)
puts maze.solve([1,1], [31,39])
end
require 'minitest'
# require 'minitest/autorun'
class TestMaze < Minitest::Test
def setup
@maze = Maze.new(10)
end
def test_maze
maze_s = <<-MAZE.chomp.split("\n").map(&:chars)
.#.####.##
..#..#...#
#....##...
###.#.###.
.##..#..#.
..##....#.
#...##.###
MAZE
maze_s.each.with_index do |row, y|
row.each.with_index do |c, x|
assert_equal c, @maze[x,y] ??#:?.
end
end
end
def test_solve
assert_equal 11, @maze.solve([1,1], [7,4])
end
end