I know it's been a few days, but just for the sake of completeness I have to add them... After doing a web search for similar puzzles I discovered a similar game named Hopido [1]. There is also a very nice page over at Rosettacode [2] where sample codes are given. It's easy to edit the source code and adjust the matrix size to the desired dimensions. On a personal side note, I might create something similar for Android as my first Unity project :-)

[1] https://gamesandinnovation.com/2010/02/10/hopido-design-post... [2] https://rosettacode.org/wiki/Solve_a_Hopido_puzzle