Good question.
Why would anyone need another Sudoku solving program, when there are already lots of them available? Why bother writing such a program ? And what is it that you can expect from it?
Helmut's Sudoku Helper is not there to solve the puzzle for you, but to help you during the solving process. The goal is not so much the final result that will be reached, but the way how to do it.
Helmut's Sudoku Helper is a tool that is designed to guide you through the solving process, but will leave you in control: for each single step, there will usually be a couple of good alternatives that are presented - together with a short explanation.
The cells that will be affected by this step are highlighted, and it is up to you to choose which step to take.
I like to solve Sudoku puzzles in newspapers. With a pen. Real ink on real paper. In a newspaper, there are no pushbuttons 'show me all possibilities'.
Same here.
This Sudoku Helper does not rely on shortcuts or computer tricks. Like with pen&paper, we start with few clues and many empty cells. One by one, the cells will be filled with 'pencil marks' and solutions
Enjoy !
You can copy/paste Sudokus from many sources all over the internet and import them into Helmut's Sudoku Helper. If the puzzle cannot be copied, or if you only have a printed version, just enter the position by hand: zeroes mean "empty", all other digits represent a solution. Like this:
000300500503819006000006000 050604072060090080230107050 000900000100763905006001000
Takes about 40 seconds.
Use as many spaces, letters or special characters as you like (+,-,|,a,b,c,*,# etc.) but do not use tabs.
The most important thing to remember is that a Sudoku has 81 cells, so there should be exactly 81 digits and/or period ('.') characters.
Yes, you can!
There are many interesting puzzles all over the web, and frequently the only option that is given by those sites is to solve them online (or they have a crummy 'print' facility that does not provide enough space to write in).
Once a puzzle is imported, Helmut's Sudoku Helper offers a COPY/PRINT action that lets you create a .pdf document ready for printing.
A perfect way to take those nice puzzles from the web with you on a plane, or solve the Sudoku at breakfast over a cup of coffee or tea.
Well, in Helmut's Sudok-o-Rama, of course!
Four puzzles every day, from easy to advanced, plus one extra puzzle in a shape slightly different from the "classic" appearance.
HSH has also been tested with puzzles from these sites:
Don't worry, you can still solve your Sudok-o-Rama puzzle!
The menu option "DO IT YOURSELF" takes you to a "no computer assistance" area where you can solve the puzzle on your device (large screen and keyboard, or handheld/mobile) like you would on paper. No restrictions, no suggestion, no help. Do whatever you like - there is only one rule: in every row (and column and ...) a number can only be used once.
Yes, indeed!
There are two ways to do this:
No problem: go explore!
Version 5.1 of the Sudoku Helper introduced a new menu action: "EXPLORE"
At any point during the process of solving a Sudoku, you can choose this option and go back and forth through the steps already taken. You can select different alternatives to see what else would have been possible, but in order to continue with one of the alternatives, it is necessary that you leave the explore mode by clicking on "new path".
The EXPLORE feature is extremely helpful in finding the one step that was overlooked during basics when doing the puzzle with pen & paper.
Sometimes one would like to send a Sudoku position to someone else, maybe to show an interesting solution, or maybe to ask for help.
The COPY/PRINT action automatically copies the current position to the clipboard, just like you would do with Ctrl-M, Ctrl-C. The information is pure text (no HTML) and comes in 4 formats to choose depending on what you want to do with it:
Insert this text wherever you like: mail, word document, maybe a Sudoku solver or maybe a Sudoku forum ...
When posting on phpbb powered forum sites, don't forget to add [code] and [/code] tags around the text, to ensure proper alignment.
This is what it looks like:
[code] +--------------------------+--------------------------+--------------------------+ | 234579 2579 234 | 134 8 49 | 14569 5679 124579 | | 23459 259 1 | 7 349 6 | 8 59 2459 | | 4789 6 48 | 5 149 2 | 149 3 1479 | +--------------------------+--------------------------+--------------------------+ | 269 4 7 | 26 269 58 | 3 1 58 | | 1 29 23 | 234 7 58 | 459 589 6 | | 36 8 5 | 136 136 49 | 7 2 49 | +--------------------------+--------------------------+--------------------------+ | 2578 3 268 | 9 26 1 | 56 4 578 | | 457 157 9 | 8 46 3 | 2 567 157 | | 248 12 2468 | 246 5 7 | 169 689 3 | +--------------------------+--------------------------+--------------------------+ [/code]
Sure you can !
Never mind if someone added additional markup to the puzzle, it will usually import ok, like this one here:
+--------------------------+--------------------------+--------------------------+ | 47 89 1 | 56 2 56 | 3 89# 4-7 | | 3 2 79 | 1 4 8 | 79* 5 6 | | 6 48 5 | 3 9 7 | 24 28 1 | +--------------------------+--------------------------+--------------------------+ | 19 16 8 | 7 36 4 | 5 23 239 | | 2 7 3 | 9 5 1 | 6 4 8 | | 5 69 4 | 8 36 2 | 1 379# 37a | +--------------------------+--------------------------+--------------------------+ | 8 34 6 | 2 1 9 | 4-7 37b 5 | | 47 5 79 | 46 8 36 | 29 1 234 | | 19 13 2 | 45 7 35 | 8 6 349 | +--------------------------+--------------------------+--------------------------+
Well, yes - wasn't that the whole point ?
Still, sometimes it happens that you may be interested only in part of the solution process. A very difficult position, maybe. Then you would like to avoid the tedious early stages and start with the 'very hard'/'fiendish' parts.
Helmut's Sudoku Helper can perform the standard solution steps (not the 'advanced' steps) automatically for you.
The AUTOMATE action will perform all basic solving steps and stop when the puzzles requires advanced methods. At any point during the automatic process, you can push the big STOP button to continue in step by step mode.
Currently, Helmut's Sudoku Helper supports:
I'm not sure if I'll ever implement xy-chains, I don't particularly care for those and never look for xy-chains in pen&paper puzzles.
A valid Sudoku must have a single (unique) solution.
Any position that makes it possible to create another solution just by exchanging two candidates (the 'deadly pattern') is not possible in a valid sudoku.
Therefore, we can eliminate all possibilities that would create such a deadly pattern.
HSH is able to identify a very common class of deadly patterns, the 'Unique Rectangle' (UR). A Unique Rectangle consists of four cells that form a rectangle and contain exactly the same two candidates. If the corners of the rectangle are confined to two boxes, then the two candidates cannot occur in the same rows, columns or boxes outside the rectangle. It would be possible to create two solutions for the Sudoku by switching the two candidates.
This is one of the 'deadly' patterns that are impossible in a valid Sudoku. At least one of the four corners must contain a different number.
The 'Unique Rectangle' method aims at avoiding such a deadly pattern. This can be accomplished by removing one or both of the DP candidates from one or more corners of the rectangle.
In many cases, this leaves a 'Naked Single' in one of the corners ('Type 1' UR), but there are other types, depending on additional strong links in one or both of the DP candidates.
Example:
+----------------+----------------+----------------+ | 3 6 29 | 7 89 5 | 4 129 18 | | 29 8 4 | 1 3 6 | 7 29 5 | | 17 17 5 | 2 89 4 | 89 3 6 | +----------------+----------------+----------------+ | 12 9 8 | 6 12 3 | 5 7 4 | | 167 4 16 | 5 17 9 | 23 8 23 | | 257 357 23 | 8 4 27 | 1 6 9 | +----------------+----------------+----------------+ | 1589 2 139 | 4 57 17 | 6 19 138 | | 4 13 7 | 9 6 8 | 23 5 123 | | 689 15 69 | 3 25 12 | 89 4 7 | +----------------+----------------+----------------+
In this position we can see candidates '2' and '3' in all four cells of the rectangle formed by rows 5 and 8 / columns 7 and 9.
If r8c9 were '2' or '3', the deadly pattern would arise. Therefore, r8c9 must be '1'.
When we find two rows, where a certain candidate is restricted to the same two columns, that is called an 'x-wing'.
When we find three rows, where a candidate is restricted to the same three columns, that is called a 'swordfish'.
Same with four rows / columns. That's a 'jellyfish'.
Both patterns are rather rare, and it is extremely unlikely that you'll ever need the method for a real Sudoku. Chances are that you'll find a couple of wings before you spot the swordfish ...
This is one of the very few examples, where a swordfish is needed:
+--------------------------+--------------------------+--------------------------+ | 3469 13469 5 | 2 3469 8 | 7 34 1346 | | 7 8 69 | 34569 34569 13459 | 36 2 1346 | | 2346 12346 26 | 3467 3467 1347 | 9 5 8 | +--------------------------+--------------------------+--------------------------+ | 2456 7 3 | 8 456 45 | 1 9 26 | | 1 2469 269 | 34679 34679 3479 | 2368 38 5 | | 569 69 8 | 1 3569 2 | 4 7 36 | +--------------------------+--------------------------+--------------------------+ | 23689 2369 4 | 359 28 359 | 238 1 7 | | 238 5 1 | 47 28 47 | 238 6 9 | | 2389 239 7 | 39 1 6 | 5 348 234 | +--------------------------+--------------------------+--------------------------+