105 lines
2.3 KiB
Ruby
105 lines
2.3 KiB
Ruby
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#!/usr/bin/env ruby
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problem = 6
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input = File.readlines("#{problem}.input").map(&:strip).map(&:chars)
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#input = DATA.read.split("\n").map(&:chars)
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DIRECTIONS = ["^", ">", "v", "<"]
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def find_start(input)
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input.each_with_index do |row, x|
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y = row.index { DIRECTIONS.include?(_1) }
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return [x,y] unless y.nil?
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end
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end
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def movement(direction)
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[[-1, 0], [0, 1], [1, 0], [0, -1]][direction]
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end
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def out_of_bounds?(input, location)
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location.first >= input.size ||
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location.last >= input.first.size ||
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location.first < 0 ||
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location.last < 0
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end
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def obstructed?(input, location)
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["O", "#"].include?(input[location.first][location.last])
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end
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def traverse(input, starting_location, starting_direction)
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location = starting_location.dup
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direction = starting_direction.dup
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visited = Hash.new { |h, k| h[k] = 0 }
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while
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visited[location] += 1
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next_location = []
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loop do
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movement = movement(direction)
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next_location = [
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location.first + movement.first,
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location.last + movement.last
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]
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break if out_of_bounds?(input, next_location)
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break unless obstructed?(input, next_location)
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direction = (direction + 1) % 4
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end
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if out_of_bounds?(input, next_location)
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return visited.keys
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elsif visited[location] > 5
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return :loop
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else
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location = next_location
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end
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end
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end
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def find_obstructions(input, nodes, start_location, start_direction)
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last_value = "."
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nodes.select.with_index do |node, i|
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# undo last mark
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if i > 0
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last_location = nodes[i - 1]
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input[last_location.first][last_location.last] = last_value
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end
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# mark node a barrier
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last_value = input[node.first][node.last]
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input[node.first][node.last] = "O"
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# traverse
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traverse(input, start_location, start_direction) == :loop
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end
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end
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path = []
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location = find_start(input)
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direction = DIRECTIONS.index(input[location.first][location.last])
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visited = traverse(input, location, direction)
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start = Time.now
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result_2 = find_obstructions(input, visited, location, direction)
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finish = Time.now
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puts "Finished in #{finish - start}"
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result_1 = visited.uniq.size
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p result_1
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p result_2.uniq.size
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__END__
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....#.....
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.........#
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..........
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..#.......
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.......#..
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..........
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.#..^.....
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........#.
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#.........
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......#...
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