Hi

I need your help to build a proper Sudoku puzzle by means of ILP modeling.

The model should derive an initial grid, from a sudoku solved, such that there exists a feasible Sudoku solution compatible to that grid and this solution is unique.

For example:

at the begining I have a sudoku solved like this:

then I remove two digits (to keep it simmetric)

remove other 2 digits

I continue to removing till the sudoku lose the constriction of unique solution

Please Help me!!!

Thank you in advance!!!