Will KSA solve Killer Sudoku puzzles for me?
No. It’s not really designed for that. It’s only designed to help out. You still need to bring your problem-solving skills. Killer Sudoku Aide (KSA) just helps narrow down some of your choices.
What is the Combinations tab for?
Any given Killer Sudoku cage for a specific size has a finite number of unique digit combinations that, when added up, will equal the sum. For some cage sizes, there can be quite a few combinations.
It’s not uncommon for players to have a chart handy listing all the combinations. KSA was created to replace that chart and take it a step or two further.
The Combinations tab in KSA allows you to input the cage dimensions and it will provide you with the digits that can exist in that cage. It shows the aggregate digits, and you can drill down for more specifics.
For Example
A cage of size 3, sum 8, can only contain the digits 1,2,3,4,5, which will be displayed on the primary grid. The Combos button will take you to detail grids showing that the two possible combinations are 1,2,5 and 1,3,4.
During the course of solving a Killer Sudoku you gather further information about what can and cannot be in a cage. That is what the Mandatory and Excluded keypads help with. Supplying information that you’ve discovered about digits that can or cannot be within a cage, will reduce the list of combinations to only those remaining.
For Example
Using the same info from the example above, selecting a mandatory digit of 2 will narrow the results to a single combination of 1,2,5. Similarly, if you excluded the 2, you’d get the single combination of 1,3,4.
What is the Possibles tab for?
The idea of Possibles is more abstract. It’s another way of manipulating the combinations. In brief, the idea is that sometimes you don’t know specifically what digit is in a cell, but you have narrowed it down to a shorter list.
With a short list of possibilities, we can filter and combine the combinations to create a list of all digits that can go in the other cells in the cage.
Let’s step through this again using our examples from above. Those examples are very simplistic, and you probably would not use the Possibles tab to solve them, but they help clearly demonstrate what the tool is doing.
Our premise here is that we have a cage of size 3, with a total of 8, and we know through some puzzle-solving that one of those three cells contains either a 2 or a 4.
If on the Possibles keypad, you entered 2, it will display 1 & 5 – the other two numbers from the only combination that contains 2 – (1,2,5.) It will not display 2 because the premise is that 2 is already in the cell. This is illustrative of what it does, but it’s not very helpful.
In the same vein, if, instead of 2, you had entered 4, it would display 1 & 3 because the only combination is (1,3,4.)
Again, that’s just for illustrative purposes. If you knew the cell was a 4, you’d enter that as a Mandatory instead, but this is about possibilities.
What you’d actually do in a case like this is to enter both 2 & 4 on the Possibles keypad. This would take all combinations with either a 2 or a 4 (in this case (1,2,5) & (1,3,4), and the result would be 1, 3 & 5. This is the union of the combinations minus the possibilities you’ve entered.
Here’s a caution. In these examples, the possibility does not show in the results because they cannot be in the other cells, but that is not always the case. Let’s consider a more complicated case.
Example
Cage Size: 4. Cage Sum: 12
No Mandatories, no Excludes
One cell contains either a 3 or a 6 (Possibles)
Result: 1,2,3,6In this case, there are two valid combinations (1,2,3,6) & (1,2,4,5). Both possibilities are in the same combination, so the second combination is filtered out. The reason also returns the 3 and the 6 is because it is the union of the two result sets (1,2,6) and (1,2,3) = (1,2,3,6)
In that example, when you solve the cell as 6, the others will contain 3, and vice versa if the cell is 3.
To use the Possibles tab, you always start with the Combinations. Setup all your information in Combinations, then switch to the Possibles tab and punch in your Possibles.
You can also further refine your Mandatories or Excludes on this screen.