1, exclusion method

Finding the only fillable space in a cell with numbers is called exclusion method, and finding the only fillable space with numbers is called elimination solution (implicit unique solution).

2. Remainder method

Finding the only number that can be filled in a lattice is called remainder method, and the only number that can be filled in a lattice is called naked list. The remainder method is a method to delete numbers that have appeared in peer groups, each of which has 20 bits.

A.

3. Relative probability

Relative probability is not the real probability, but the possibility of comparing several numbers in the same cell. Relative probability = probability of nine squares appearing × probability of rows appearing × probability of columns appearing.

Extended data:

Sudoku (shdú) is a mathematical game, which originated in Switzerland in the18th century. It's a logic game with paper and pen. Players need to infer the numbers of all remaining spaces according to the known numbers on the 9×9 disk, and ensure that the numbers in each row, column and thick line palace (3*3) contain 1-9, which is not repeated.

Sudoku is nine palaces, and each palace is divided into nine squares. Give some known numbers and problem-solving conditions in this eighty-one box, and use logic and reasoning to fill in the numbers of 1-9 in other blanks. Make each number of 1-9 appear only once in each row, column and palace, so it is also called "Jiugongge".

There are many factors that affect the difficulty of Sudoku. As far as the topic itself is concerned, it includes the most difficult skills, the times of using various skills, whether there are hidden and hidden skill combinations in depth and breadth, and the number of numbers that can be logically deduced from the current disk.

For players, the number of skills, proficiency and observation naturally affect the difficulty judgment of a problem. Sudoku publications on the market are mixed, and the difficulty listed in books, newspapers and magazines or the time for solving problems by the public is purely for reference. The difficulty is often misplaced, so don't pay special attention to it.