terras5.rb

def f2(n)
	return n.odd? ? (n * 3 + 1) / 2 : n / 2

end

def re(n, t)

	s = (n % 2).to_s
	n1 = n
	t.times \
	{
		n = f2(n)
		s << (n % 2).to_s
		break if (n == 1)
	}
	return s, n
end

def adj(x, m, n, s2, p2, p, x3)
	s2.replace(p[0...x] + (x3 % 2).to_s)
	m = (s2[x, 1] == p[x, 1])
	n = p2.reverse.to_i(2)
	p2[x, 1] = m ? '11' : '01'
	return m, n, x3
end

#srand(5)

p = (1..20).map { rand(2) }.join


p2 = ['01', '11'][p[0, 1].to_i]
n = 1
n3 = 0
m = p2 == '11'
x3 = (p2.reverse.to_i(2)) >> 1

(1...p.length).each \
{
	|x|

	if (!m)
		ns = n.to_s(2)
		ns[0, 1] = ''
		m1 = x3 - 3**n3
		n1 = f2(m1)
	end

	n3 = p[0...x].split('').select { |z| z == '1' }.size
	
	s2 = ''
	m, n, x3 = adj(x, m, n, s2, p2, p, m ? (f2(x3) + 3**n3) : (n1 + 3**n3))

	t = s2[0...x] == p[0...x]
	p({'k' => x, 'w_i' => s2, 'n' => n, 'n_2_r' => n.to_s(2).reverse, 'X' => x3, 't' => t})
	
	s, n2 = re(n, x)
	
	raise if (!t)
	raise if (s != s2)
	raise if (n2 != x3)
}

n = p2.reverse.to_i(2)
s, n2 = re(n, p.length - 1)
p({'k' => p.length, 'w_i' => s, 'n' => n, 'n_2' => n.to_s(2).reverse, 't' => p == s})