YES(?,O(n^2))
TRS:
 {
     f(a, empty()) -> g(a, empty()),
  f(a, cons(x, k)) -> f(cons(x, a), k),
     g(empty(), d) -> d,
  g(cons(x, k), d) -> g(k, cons(x, d))
 }
 DUP: We consider a non-duplicating system.
  Trs:
   {
       f(a, empty()) -> g(a, empty()),
    f(a, cons(x, k)) -> f(cons(x, a), k),
       g(empty(), d) -> d,
    g(cons(x, k), d) -> g(k, cons(x, d))
   }
  Matrix Interpretation:
   Interpretation class: triangular
          [X3]  [X1]    [1 2][X3]   [1 0][X1]   [0]
   [cons]([X2], [X0]) = [0 1][X2] + [0 1][X0] + [2]
   
             [3]
   [empty] = [2]
   
       [X3]  [X1]    [1 2][X3]   [1 0][X1]   [0]
   [g]([X2], [X0]) = [0 1][X2] + [0 1][X0] + [1]
   
       [X3]  [X1]    [1 2][X3]   [1 3][X1]   [0]
   [f]([X2], [X0]) = [0 1][X2] + [0 1][X0] + [1]
   
   
   Qed