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90 lines
1.6 KiB
90 lines
1.6 KiB
require "minitest"
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class Spiral
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def initialize
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@square = [0,0]
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@dir = [1,0]
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@steps = [1, 1]
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end
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def each
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return enum_for(__method__) unless block_given?
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loop do
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yield @square
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step!
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end
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end
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private
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def step!
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@steps[0] -= 1
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@square = @square.zip(@dir).map {|i,j| i+j }
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if @steps[0] == 0
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change_dir!
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@steps << next_steps
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@steps.shift
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end
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end
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def change_dir!
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@dir = case @dir
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when [1,0]
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[0,1]
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when [0,1]
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[-1,0]
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when [-1,0]
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[0,-1]
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when [0,-1]
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[1,0]
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else
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raise "invalid dir: #@dir"
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end
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end
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def next_steps
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case @dir
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when [1,0]
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@steps[1]
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when [0,1]
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@steps[1] + 1
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when [-1,0]
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@steps[1]
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when [0,-1]
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@steps[1] + 1
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else
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raise "invalid dir: #@dir"
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end
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end
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end
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if $0 == __FILE__
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if ARGV.shift == "test"
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require "minitest/test"
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else
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input = ARGF.read.to_i
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p Spiral.new.each.with_index.find {|_,i| i == input - 1 }.first.sum
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end
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end
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class TestSpiral < Minitest::Test
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def test_spiral
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spiral = Spiral.new
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e = spiral.each
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assert_equal [0,0], e.next
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assert_equal [1,0], e.next
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assert_equal [1,1], e.next
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assert_equal [0,1], e.next
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assert_equal [-1,1], e.next
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assert_equal [-1,0], e.next
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assert_equal [-1,-1], e.next
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assert_equal [0,-1], e.next
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assert_equal [1,-1], e.next
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assert_equal [2,-1], e.next
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spiral = Spiral.new
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assert_equal [0,-2], spiral.each.with_index.find {|_,i| i == 22 }.first
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end
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end
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