Sudoku Backtracking algorithm not working

[last kestrel]

I believe that i've implemented the algorithm, yet when i try to solve the puzzle it will run for a while then tell me that no solution exists (a solution does exist). attached is my source code and the puzzle

[noble dirge]

When your question is answered use !solved to mark the question as resolved.

Remember to ask specific questions, provide necessary details, and reduce your question to its simplest form. For tips on how to ask a good question use !howto ask.

[jagged oyster]

have you tried stepping through your program in a debugger

[plain lintel]

debug debug debug and then debug more

🙂