Twelve constellations Sudoku

Avoidable Rectangle is a technique to "reverse" the unique rectangle deletion method: after all three vertices of the "rectangle" are filled, it is found that the fourth vertex must not be filled with numbers that constitute a fatal pattern.

As shown in figure 1, when we do this, we find that A, B and D are all filled with numbers. If we put these three squares and c together, it just constitutes "9-?" -9-4 inch structure. C is an unknown number. C If you fill in 4, it will constitute the fatal structure of "9-4-9-4", so it is wrong to fill in 4, so C≠4. Get the solution c = 1.

All four vertices must be the numbers we fill in, and there can be no hints. Because deadly patterns are filled in by ourselves, once there is a prompt number, we will reason according to the prompt number, so there will be no case of judging whether it can be filled in according to uniqueness.