YES
O(n^4)
TRS:
 {
     ++(x, nil()) -> x,
  ++(++(x, y), z) -> ++(x, ++(y, z)),
     ++(nil(), y) -> y,
   ++(.(x, y), z) -> .(x, ++(y, z))
 }
 DUP: We consider a non-duplicating system.
  Trs:
   {
       ++(x, nil()) -> x,
    ++(++(x, y), z) -> ++(x, ++(y, z)),
       ++(nil(), y) -> y,
     ++(.(x, y), z) -> .(x, ++(y, z))
   }
  Matrix Interpretation:
   Interpretation class: triangular
       [X7]  [X3]    [1 0 0 0][X7]   [1 0 0 0][X3]   [0]
       [X6]  [X2]    [0 0 0 0][X6]   [0 0 0 0][X2]   [0]
   [.]([X5], [X1]) = [0 0 0 0][X5] + [0 0 1 0][X1] + [0]
       [X4]  [X0]    [0 0 0 0][X4]   [0 0 0 1][X0]   [1]
   
           [1]
           [0]
   [nil] = [0]
           [1]
   
        [X7]  [X3]    [1 0 0 1][X7]   [1 0 0 0][X3]   [0]
        [X6]  [X2]    [0 1 0 0][X6]   [0 1 0 0][X2]   [0]
   [++]([X5], [X1]) = [0 0 1 0][X5] + [0 0 1 0][X1] + [0]
        [X4]  [X0]    [0 0 0 1][X4]   [0 0 0 1][X0]   [1]
   
   
   Qed