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require "minitest"
class Spiral
def initialize
@state = [0,0]
end
def each
return enum_for(__method__) unless block_given?
(1..Float::INFINITY).lazy
.flat_map {|i| [i, i] }
.zip(%i[r u l d].cycle)
.flat_map {|n,d| Array.new(n, d) }
.each do |dir|
yield @state
@state = @state.zip(
case dir
when :r
[1, 0]
when :u
[0, 1]
when :l
[-1, 0]
when :d
[0, -1]
end
).map {|a,b| a + b }
end
end
end
class Grid
def initialize
@grid = Hash.new {|h,(x,y)|
neighbors = [[-1, 1], [0, 1], [1, 1],
[-1, 0], [1, 0],
[-1,-1], [0,-1], [1,-1]]
h[[x,y]] = neighbors
.map {|i,j| [x+i,y+j] }
.select {|i,j| h.has_key?([i,j]) }
.map {|i,j| h[[i,j]] }
.sum
}
@grid[[0,0]] = 1
end
def [](x,y)
@grid[[x,y]]
end
end
if $0 == __FILE__
case ARGV.shift
when "test"
require "minitest/autorun"
when "0"
input = ARGF.read.to_i
p Spiral.new.each.with_index.find {|_,i| i == input - 1 }.first.sum
when "1"
input = ARGF.read.to_i
grid = Grid.new
p Spiral.new.each.lazy.map {|x,y| grid[x,y] }.find {|value| value > input }
end
end
class TestSpiral < Minitest::Test
def test_spiral
spiral = Spiral.new
e = spiral.each
assert_equal [0,0], e.next
assert_equal [1,0], e.next
assert_equal [1,1], e.next
assert_equal [0,1], e.next
assert_equal [-1,1], e.next
assert_equal [-1,0], e.next
assert_equal [-1,-1], e.next
assert_equal [0,-1], e.next
assert_equal [1,-1], e.next
assert_equal [2,-1], e.next
spiral = Spiral.new
assert_equal [0,-2], spiral.each.with_index.find {|_,i| i == 22 }.first
end
end
class TestGrid < Minitest::Test
def test_grid
grid = Grid.new
assert_equal 1, grid[0,0]
assert_equal 1, grid[1,0]
assert_equal 2, grid[1,1]
assert_equal 4, grid[0,1]
assert_equal 5, grid[-1,1]
assert_equal 10, grid[-1,0]
end
end