submission 1 submission 2

Is it because of the bitwise operators? If so, why?

Problem Link: Sudoku Solver

My code: link

Pretty straightforward problem. I tried sorting the blank points on the basis of options for a point. I also tried with simple backtracking. In both cases I got TLE.

What am I missing here?

Also, is there any way to use bits to mask which number is possible for a place(row/column/box)?