Sudoku and Solver

This website is for the elderly and young men and women of all types, from beginners to advanced class, to enjoy Sudoku using Sudoku Solver which was developed by author of this website and can solve "The World's Hardest Sudoku". It is a gentle commentary, so anyone can understand the essence of the Sudoku. The rules of the Sudoku are easy, but there is a deep puzzle with fans all over the world. Come on, let's all enjoy the brain training workout!

According to Dr. Arto Inkala, Finland, who developed The World's Hardest Sudoku, “To solve Sudoku, there is no need to be able to add. Logical thinking, attention, and perseverance are needed”. The World's Hardest Sudoku sample and solution are as follows.

1. What is the Sudoku?

It is a puzzle that arranges the numbers from 1 to 9 on the board of 9X9. The rules are quite simple, only that the numbers do not overlap in the vertical, horizontal or 3X3 area.

☆ Rule 1: Each column must have the numbers 1-9

☆ Rule 2: Each row must have the numbers 1-9

☆ Rule 3: Each 3X3 block must have the numbers 1-9

Howard Garns of the United States in 1979 made this puzzle a "Number Place", but did not hit too much. The name Sudoku was born in 1984 from Nikoli's "The numbers are limited to single". New Zealander Wayne Gould has developed a program to create Sudoku, which has been well received by The Times in the UK in 2004. After that, it became popular under the name of "Sudoku" or "Number Place" in the wave of internationalization. Sudoku is a puzzle for brain training, which anyone can enjoy regardless of language.

Note: The name "Sudoku" is a registered trademark of NIKOLI co.,ltd in Japan. Outside of the company, the name "Number Place" is used.

2. Display method and coordinates

In this website, for convenience, vertical rows (rows), horizontal columns (columns), 3X3 cells are called areas (also called blocks), and squares are called cells.

← Area

↑ cell

The coordinates are displayed in the area (row, column), so the coordinates of the cell★ become H (5i).

Moreover, in this website, each technique is displayed as follows for convenience.

B technique 1 (Fill in the sideways)

↑ ↑ ↑

Class Technique # (Technique Name)

3. How to solve the Sudoku

There are two ways to solve a human being and a computer(Sudoku Solver) in the same way.

□ Human being

A: Logical / Rationale

It is the main stream of how to solve Sudoku, a royal road. We will fill in the cells one by one in Logical. In this website, three classes are defined as follows,

*Beginner: required simple Sudoku rules

*Intermediate: required a close scrutiny of numbers

*Advanced: required advanced techniques for difficult questions and super challenges

B: Hypothesis method

If it can not be solved logically, We will solve it assuming a certain number of cells (IF ...). If a contradiction occurs, the assumption is incorrect and we will solve it with other possible numbers. If you use the hypothesis method, it will take time, but you can always solve the sample. This work is "manual labor" and not "brain labor". As a rule, this method is not always used as a treasurer of the House when solving super puzzles in the last and last part of the "forbidden hand".

□ Sudoku Solver

A: Logical / Rationale

Sudoku Solver is poor at intermediate class and higher techniques. Even with techniques that humans can understand relatively easily, it is very difficult to translate the algorithm into software.

B: Hypothesis method

The computer is good at the hypothetical method. In this Sudoku Solver, trial and error are implemented by temporarily placing it in three steps.

*Step1: Logical calculation by adding one possible two-digit number, if it is not possible

*Step2: In addition to step1, logical calculation by adding 2 possible 2 numbers, if not

*Step3: In addition to step 2, perform logical calculations by adding one possible two-digit number.

In the final step3, 1 + 2 + 1 = 4 numbers are added to perform logical calculations.

Now the world's hardest Sudoku can finally be analyzed.

The Sudoku samples can be analyzed in 4 levels by Sudoku Solver in this web site, which are beginner, intermediate, advanced and super.

4. Sudoku and newspaper / monthly magazine in Japan

Sudoku is a puzzle loved by everyone, so it is also published in the leading daily newspaper in Japan.

The A newspaper is published Sudoku column every Saturday. The difficulty level is indicated by the number of ★, and the basic class of this website in ★★★, the intermediate class in ★★★★, and the advanced class in ★★★★★.

The N newspaper is also published every Saturday, and the skill of the reader is displayed here in the required time. It is possible to answer 100% by the technique of this intermediate class to solve this website.

In the B-monthly magazine, a beginner class problem has been published with the name Sudoku as "Essential and Thinking Puzzle". 10,000 yen will be sent to 10 people by lottery for the correct person. It is a simple matter, so the probability of winning will be similar to a lottery.

5. Sudoku common sense quiz

Then, please try to the Sudoku common sense quiz.

If the following question is correct, put ○ in ( ), and if incorrect, put X in ( ) and correct it. You don't have to be so serious because it's a play.

( ) Q1: This puzzle has a Japanese name for Sudoku and an English name for Number place.

( ) Q2: Sudoku is not a puzzle except for numbers.

( ) Q3: It is better to have a mathematical background to solve Sudoku.

( ) Q4: The simpler Sudoku, the larger the number of given cells and the fewer empty cells.

( ) Q5: There are never more than one solution in Sudoku.

( ) Q6: A minimum of 15 given cells are required for Sudoku to become a sample.

( ) Q7: The most difficult sample that cannot be answered using the hypothesis method (temporary placement).

( ) Q8: A minimum of one day is required to solve the “The World Hardest Sudoku” problem logically.

( ) Q9: The famous technique called XY wing can be applied even if the number is 3 digits and the condition is satisfied.

( ) Q10: Not all samples can be analyzed even with excellent Sudoku solver.

Please see here for the answer ↓.

*Introduction to the author

When author was 70 years old, he started Sudoku as part of his brain training, and he is still practicing "Sudoku Studies". he learned VBA(Visual Basic for Applications) to develop the Sudoku analysis software, and completed "Sudoku Solver" which is used in this website.

* Note *

This website is published as comments of a personal hobby. As it does not guarantee the accuracy, feasibility, uniqueness etc. of the contents, please refer to each person's responsibility. This website has no responsibility for the result. In addition, the contents of this publication and the modification and unauthorized conversion etc. of the program are strictly prohibited.

"Sudoku" is the registered trademark of NIKOLI co.,ltd.

"VBA","OFFICE/Excel" are the registered trademark or trademark of Microsoft Corporation(US).

****** All contents may be subject to change without notice *******