群のなんか

test.rb

def apply(x, k)
  ret = []
  x.each.with_index{|a, i| ret[i] = k[a-1] }
  ret
end

def dim(x)
  t, i = x, 1
  loop do
    t = apply(t,x)
    # p i:i, t:t
    break if t == x
    i = i+1
  end
  i
end

def applya(a, x)
  t = a
  x.each{|tt| t = apply(t, tt) }
  t
end

def applyx(x)
  t = x.pop
  applya(t, x)
end

# [a1,a2].repeated_permutation(2).each{|x| print x if s4 == applyx(x) }