How can I use computational methods when creating a sudoku game?

I'm so confused? I know it's about abstraction, decomposition, backtracking and pattern recognition but how are these used when developing a sudoku game ?

decomposition: splitting a task into smaller, more manageable and maintainable sections. So if you split your code into Main Menu / Generating Sudoku / Player Input / Identifying Player Errors / End Screen, that would be decomposition. Abstraction is creating a UI that doesn't show the user unnecessary information - for example, they don't need to know your variable names, how the puzzle was generated, what file it's being stored in.