The New Sudoku Players' Forum

[Trinkles]

I printed out a few puzzles from the trial version of the the downloadable sudoku, I'm pretty positive all my numbers are correctly placed but just to make sure I didn't miss anything how can i check my answers now?

[scrose]

There are two ways.

If you know what the starting grid looks like, you can "dub" it into the program by going to File > Dub or pressing Ctrl + U. Once you have the starting grid dubbed in, click the Verify button. If the grid checks out, click the Play button. Then go to Edit > Show Solution and check if the results match your own.

The nice thing about the Pappocom puzzles is that each one has a unique solution. So, if you no longer have the starting grid, as long as your answer has the digits one through nine in each row, column, and block without any repeats, then you know you have the correct answer.

[lobby__boy]

i do all of mine on paper, and the fastest (though a little bit stoneage) way i've found is just to count all of the rows,columns and squares to be sure there are no doubles. tedious at times, but it's kindof a relief after having completed the puzzle.

[Francisco]

Simple:

Every BOX, ROW or COLUMN sum has to be 45 (1+2+3....+9=45)

I do mine with excel (sometimes in paper) and that's the fastest way to check:

I sum and count every row, column and box: when finished the sum must be 45 and the count must be 9 (number of numbers).

[Animator]

Actually you can have the number 45 for each box, row and column and have an incorrect grid. Ofcourse it requires that you made more then one mistakes, but that is usually the case ...

Take this incorrect grid for example:

1 2 3 | 3 8 4 | 7 8 9
4 5 6 | 8 6 9 | 1 3 3
7 8 9 | 1 1 5 | 4 4 6
-----------------------
2 3 1 | 5 6 4 | 8 9 7
5 6 4 | 8 9 7 | 2 3 1
8 9 7 | 2 3 1 | 5 6 4
-----------------------
3 1 2 | 6 4 5 | 9 7 8
6 4 5 | 9 7 8 | 3 1 2
9 7 8 | 3 1 2 | 6 4 5

I'm not 100% sure with what you mean with the following sentence: 'the count must be 9 (number of numbers).' Do you mean: that there must be 9 different numbers, or that there simply should be 9 numbers. (In the second case it is irrelevant wheter or not there are duplicates numbers in a row)

[Francisco]

Actually you can have the number 45 for each box, row and column and have an incorrect grid. Ofcourse it requires that you made more then one mistakes, but that is usually the case ...

Take this incorrect grid for example:

1 2 3 | 3 8 4 | 7 8 9
4 5 6 | 8 6 9 | 1 3 3
7 8 9 | 1 1 5 | 4 4 6
-----------------------
2 3 1 | 5 6 4 | 8 9 7
5 6 4 | 8 9 7 | 2 3 1
8 9 7 | 2 3 1 | 5 6 4
-----------------------
3 1 2 | 6 4 5 | 9 7 8
6 4 5 | 9 7 8 | 3 1 2
9 7 8 | 3 1 2 | 6 4 5

I'm not 100% sure with what you mean with the following sentence: 'the count must be 9 (number of numbers).' Do you mean: that there must be 9 different numbers, or that there simply should be 9 numbers. (In the second case it is irrelevant wheter or not there are duplicates numbers in a row)

Well, you're right that those add 45, but I would have to be blind not to see those mistakes

Usually, I'm play with attention to the ones I'm missing, but when I reach a count of 7 (in a row, line or column) I just check which ones I'm missing, so I have a method that works well for me... Lets say that the sum and the count work as an extra insurance

[lobby__boy]

i think what he meant was, "there must be 9 9s, 9 8s, 9 7s, etc...)

[Francisco]

i think what he meant was, "there must be 9 9s, 9 8s, 9 7s, etc...)

Actually no...

But now I remembered an insurance!

I could sum 1²+2²+3²+...9² and check if this was true to every row, line and box

[lobby__boy]

interesting

[Francisco]

interesting

The Square thing WORKS

I used it in Animator puzzle, and only the ones with the 9 different numbers get the right value (285)

[lobby__boy]

that is quite interesting. i didn't quite understand it before...clarification makes all the difference. wow...kudos on that one

[Animator]

Summing 1², 2², ... will be a lot tricker to fool, but I'm not sure that it is impossible...

But what's the bottom line of the question? How to verify a grid easily, as a human...

Do you really want to do that yourself for every row, column and box? I guess not...

A computer can ofcourse do it easily... but it can be done just as easy as checking if each of the nine numbers occures in each row, column and box...

[Francisco]

Summing 1², 2², ... will be a lot tricker to fool, but I'm not sure that it is impossible...

I'm sure it's impossible

But if you want something else you could put an IF condition to check if the 9 numbers are all different, a way to check it would be to multiply:

If number =1 then 1*100000000
If number =2 then 2*10000000
If number =3 then 3*1000000
...
If number =8 then 8*10
If number =9 then 9*1

sum them and you would have 123456789. If this wasn't the result then something is amiss...

[lobby__boy]

some interesting mathematical deductions...i think i'm with Francisco in it being impossible.[/quote]

[Animator]

Both of you are incorrect...

Calculate 4² + 5² + 6², then calculate 2² + 3² + 8². The result is the same, meaning that the sequence 4 5 6 can be replaced with 2 3 8. (I'm pretty sure there are other combinations aswell, but I only care about one, since that prooves my point)

An example (incorrect) grid:

1 2 3 | 2 3 8 | 7 8 9
4 5 6 | 7 8 9 | 1 2 3
7 8 9 | 1 2 3 | 4 5 6
-----------------------
5 6 4 | 8 9 7 | 2 3 1
2 3 1 | 3 8 2 | 8 9 7
8 9 7 | 2 3 1 | 5 6 4
-----------------------
6 4 5 | 9 7 8 | 3 1 2
3 1 2 | 8 2 3 | 9 7 8
9 7 8 | 3 1 2 | 6 4 5