One of the test case is:

input: [".87654321","2........","3........","4........","5........","6........","7........","8........","9........"]

and the expected answer is: true

I understand that above Sudoku input is valid if we only check the row+column+square conflict.

However, there is no valid solution for above Sudoku, isn't it?

Or I missed something important here?

Thanks.