I build an "AI" in C++ and it was able to find a checkmate

This is the game:

1. Nf3 Nf6

2. Ne5 Ne4

3. f4 f6

4. Ng4 d5

5. Ne3 d4

6. Nc4 b5

7. Na5 Bg4

8. Nb3 Qd5

9. d3 Nd6

10. Nd2 Nc6

11. h4 Rd8

12. a3 a5

13. Rh2 a4

14. e4 Qe6

15. Nd4 Nd4

16. Be2 Be2

17. f5 Nf5

18. f5 Qe3

19. Ne4 Qg1+

20. Kd2 Qd1+

21. Kc3 Qc2+

22. Kb4 Qb3+

23. Kc5 Rd5#

my code is 650 lines and it includes printing a chessboard matrix