input = DATA.readlines(chomp: true)
  .flat_map.with_index {|line, j|
    line.chars.map.with_index {|x, i|
      [[j,i], x]
    }
  }.to_h

turns = {
  [-1,0] => [0,1],
  [0,1] => [1,0],
  [1,0] => [0,-1],
  [0,-1] => [-1,0],
}

start = input.find { _2 == ?^ }.first
dir = [-1,0]
path = [start]
loop do
  peek = path.last.zip(dir).map {|i,di| i + di }
  case input.fetch(peek, nil)
  when ?.
    path << peek
  when ?^
    path << peek
  when ?#
    dir = turns.fetch(dir)
  when nil
    break
  else
    fail
  end
end

pp path.to_set.length

__END__
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