TOPICS

1. Is it easy sample that there are many given cells ?
No, the number of given cells and the difficulty of the sample are not necessarily proportional. Examine the following sample using Sudoku Solver. Although Topic 1(Given 17 cells) seems to be a very difficult sample.
Topics 1 (Given 17 cells) Topics 2 (Given 22 cells)

The results analyzed by Sudoku Solver are as follows.
The Topics 1(Given 17 cells) is easy to solve at the intermediate level, but Topics 2(Given 22 cells) is the super level, and it is a very difficult sample to solve with trial and error for 7 seconds.

2. Are there multiple solutions at single sample ?
Yes, there are more than one correct solution for a single sample, and there may be multiple solutions. For example, as an extreme example, if there is only one given cell, there will probably be countless solutions. According to the authority of the way, it seems that it is necessary to enter more than given 13 cells in the initial state to become one solution (12 or less solutions will be more than one).
See the following sample. The green cells in sample contain 2 and 5 but there are 2 correct solutions.
Sample Solution 1 Solution 2
　　　

In general, samples with multiple solutions are said to be incomplete failure in Sudoku. It is said that there are no samples with multiple solutions in the books that you buy in a bookstore.

3. What is the minimum given cells to require as a sample ?
According to a study by Irish mathematician McGuire, after a great deal of time researching on a super computer, at least 17 cells need to be given in order for a sample.

4. Sudoku is a pattern recognition
The Sudoku is not a calculation that uses numbers, just because it is a number place. It is just pattern recognition. Therefore, even if you use alphabets A to Z or symbols ○△□ and other than numbers, you can create a sample as a puzzle.
Here, let's convert the numbers 1 to 9 with A to I, ○ to ▽.
　　　　　　Convert table⇒

　1) Numbers (1 to 9) This is the Sudoku.

2) Alphabets (A to I)

3) Symbols (○ to ▽)

How about that? After all it turns out that the numbers are the easiest to do with Sudoku.

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*Version

date	version	notes
2019.9.1	β	β released
2019.9.8	1a	1st released
2020.10.24	1d	updated
2022.8.17	1e	updated