I have to implement algorithm, where input and output go as follows:

Input:

Code,
Catenation of x1,x2,…,xn with respect to a merging function, where x1,x2,…,xn belong to a code - see example 2, page 4 from Directed figure codes are decidable by Michal Kolarz and Wlodzimierz Moczurad,
Catenation.

Output: x1,x2,…,xn

Please refer to the definitions...