YES(?,O(n^1))
TRS:
 {f(a(), x) -> f(b(), x),
  f(a(), x) -> g(a(), x),
  g(a(), x) -> f(b(), x)}
 DUP: We consider a non-duplicating system.
  Trs:
   {f(a(), x) -> f(b(), x),
    f(a(), x) -> g(a(), x),
    g(a(), x) -> f(b(), x)}
  Natural interpretation:
   Strict:
    {f(a(), x) -> f(b(), x),
     f(a(), x) -> g(a(), x),
     g(a(), x) -> f(b(), x)}
   Weak:
    {}
   Interpretation class: stronglylinear
   [b] = + 0
   [a] = + 2
   [g](X1, X0) = + 1*X0 + 1*X1 + 5
   [f](X1, X0) = + 1*X0 + 1*X1 + 6
   
   Qed