How to play with a sudoku puzzle
Showing a problem
We assume that you installed kaidoku and got into kaidoku prompt. Just type c and a problem is shown.
kaidoku-1.0.1> c
Level 2 No. 1
1 2 3 4 5 6 7 8 9
+-----+-----+-----+
1|9 |8 5 |2 1 4|
2|5 4 2|1 6 3| 7 |
3|8 | 2| 3|
+-----+-----+-----+
4|3 1| 4| 7|
5| 7 |3 6| 2 |
6|2 |9 |4 5|
+-----+-----+-----+
7|1 |6 | 2|
8| 2 |7 1 5|3 4 8|
9|7 3 8| 4 9| 6|
+-----+-----+-----+
Type 3 digits (row, column, number) to put a number. i for hint.
kaidoku-1.0.1>
Kaidoku is shipped with sudoku problems of different levels of difficulty. At the first time you run kaidoku, level 2 is selected. Therefore, “Level 2 No. 1” is shown.
Creating an image file
You can now start solving this problem, but before doing it, you may want to see the image of the problem. At first, you should explicitly create an image file with jpg command to designate the directory of the data file. Default data directory is ~/kaidoku. If you prefer other directory, input the directory when it is prompted.
kaidoku-1.0.1> jpg
Data directory does not exist.
Input name of the data directory (default: ~/kaidoku):
See image by "html".
kaidoku-1.0.1>
If you get an error message of OSError: Unable to locate Ghostscript on paths, make sure that Ghostscript is installed in your system and the paths to Ghostscript is properly set, as explained here.
Now this image file is created as current.jpg in the data directory.
Now run html and a html file showing this image file is opened with your default web browser. The html file reloads the image file every 2 seconds (interval can be adjusted with a text box). From now on, as you proceed with this problem, the image file is updated and the html file reloads, so that it is easy to follow the change in the state of the board.
Put a number
Now we are ready to play. Look at the above figure and think where to start.
Look at row 2, column 9. Here, it means that
- Row 2 means a 2nd row from the top
- Column 9 means a 9th column from the left
It can also be written as R2C9. Scan row 2. It has all the digits from 1 to 9 except 8 and 9. Therefore, R2C9 should have 8 or 9. In column 9, there is 8 on R8C9, and therefore R2C9 should not be 8. Therefore, R2C9 should be 9.
When you want to know which number is to be placed in a certain cell, you scan the same row, column, and box. From the digits 1 to 9, the number already filled in the same row, column, and box is removed from the candidate. If there is a unique candidate, that is the number to be filled in that cell. This logic is called naked single. By using the naked single logic, R2C9 is 9.
Now we place number 9 on R2C9. Please look at the instruction of Type 3 digits (row, column, number) to put a number. You specify row, column, and number to place in this order. In this case, row is 2, column is 9, number is 9, and therefore you type 299.
kaidoku-1.0.1> 299
The ascii image of the board is shown and the image file shown in the html file updates automatically as follows. The last move is shown in green letter.
Keep on solving
Now row 2 has only one blank cell, and it is easy to see that R2C7 is 8. Column 9 has only one blank cell and R5C9 is 1. By the naked single logic, R8C1 is 6. After that, column 1 has only one blank cell and R5C1 is 4. Row 8 has only one blank cell and R8C3 is 9. Put these numbers as follows.
kaidoku-1.0.1> 278
kaidoku-1.0.1> 591
kaidoku-1.0.1> 816
kaidoku-1.0.1> 514
kaidoku-1.0.1> 839
Notifying a mistake
When you put a number that is unable to be placed, the number is not placed. For example if you type 722 in this situation, warning message is shown as follows.
kaidoku-1.0.1> 722
Both R7C2 and R7C9 have the same value of 2.
Take back a move
You can always erase a number that was written at the last time. Just type b.
kaidoku-1.0.1> b
Level 2 No. 1: move 5
Writing a number is regarded as a “move”, and we call canceling the last move as “take back a move”. You can take back as many moves as possible, until you reach the initial position.
Quit and restart
You can always quit the game by q. The status is saved in configuration file, and when you run kaidoku next time, you can start from the position where you quitted last time. Just type c or html to show the position and continue.
Finish a problem and go to the next problem
This problem can be solved with only the naked single logic. When you fill out all the blank cells, a massage appears that
Now this problem is solved !
You can go to the next problem with n.
kaidoku-1.0.1> n
Level 2 No. 2