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December 3, 2017 16:49
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aoc-2017-p2.rb
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| class SpiralFantasy | |
| def initialize(number) | |
| @number = number.to_i | |
| @grid = { Complex(0,0) => 1 } | |
| end | |
| def call | |
| draw.values.max | |
| end | |
| private | |
| def draw | |
| start = Complex(0,0) | |
| directions = [ :right, :up, :left, :down ] | |
| while(@grid.values.max <= @number) do | |
| case directions[0] | |
| when :right | |
| start += Complex(1,0) | |
| @grid.merge!({ start => next_cell(start) }) | |
| directions.rotate! if start.real == -(start.imag - 1) | |
| when :up | |
| start += Complex(0,1) | |
| @grid.merge!({ start => next_cell(start) }) | |
| directions.rotate! if start.real.abs == start.imag.abs | |
| when :left | |
| start += Complex(-1,0) | |
| @grid.merge!({ start => next_cell(start) }) | |
| directions.rotate! if start.real.abs == start.imag.abs | |
| when :down | |
| start += Complex(0,-1) | |
| @grid.merge!({ start => next_cell(start) }) | |
| directions.rotate! if start.real.abs == start.imag.abs | |
| end | |
| end | |
| @grid | |
| end | |
| def next_cell(current) | |
| keys = [ | |
| current + Complex(-1, 0), | |
| current + Complex( 1, 0), | |
| current + Complex( 1, 1), | |
| current + Complex(-1,-1), | |
| current + Complex(-1, 1), | |
| current + Complex( 1,-1), | |
| current + Complex( 0, 1), | |
| current + Complex( 0,-1), | |
| ] | |
| @grid.values_at(*keys).compact.inject(:+) | |
| end | |
| end | |
| puts SpiralFantasy.new(ARGV[0]).call |
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Usage:
ruby spiral_fantasy.rb 325489