1, know Jiugongge, whether it is horizontal or vertical, Jiugongge is a palace, and the numbers are different from each other until nine are together.
Fill in the unique remainder, and there is only one number left in the palace. Fill in the numbers and you'll pass.
3, exclusion method, three lines and three columns, one for each, nothing else for me to put around.
4. Hypothetical method, there are two kinds of numbers in the grid. Once you try, if there is a mistake in the derivation, you will be transposed, and if it is correct, it will be correct.