You are right, it has a diagonal symmetry. Also, I didn't notice the even-odd "game" on this puzzle. Thanks for the explanation

Fred

That (the theme) is also the reason why the 6X6 irregular ones turned out to be tougher than usual, as noted by some participants. Thankfully, they were not in the first page of the pdf.

Sorry to harp back to ISC challenge, but I need some help in solving smashed sums, deficit and shifted sudokus. I am unable to go beyond a point in deficit whereas in the other two, I don't even know where to start. I also need help with the 6x6 of which I could solve only two. The last one in the left side column and all three in the right side column have proved difficult for me.

Here are the steps for Top Right 6X6 Sudoku.



In the last image here, I use something called "Placeholder". It can be explained like this : Lets say R1C5=X. So X can be 2 or 3 or 5. Then R2C3 = X, and then R5C1=X. Now where does X go in box6, and what will be its value?

Placeholder can be used to solve some of the other 6X6 that you have found difficult. I will be posting steps for them, but it will take a while (to create the images.)

Shifted Sudoku is as good as a classic, you just need to modify your region-wise reasoning, and concentrate on rows and columns too. At the start it is advisable to focus a lot more on rows and columns till you are able to adapt to the different ways the shifted regions come into consideration.

Smashed Sums becomes a lot easier if you mark (say by circle), the cells that must contain a number. Use the logic like "this sum is so big, it'll require at least 6 cells in between 2 shaded cells, so whatever way I look, some cells will always be between the sum, and so can't be shaded" and mark circles for wherever shaded cells can't be. That and sums will help you progress.

I won't tell you anymore for now, since you couldn't find where to start. Sometimes its just about grasping the rules and then you might be able to solve it yourself which is obviously the best way forward, but feel free to ask if still stuck.

Thank you very much, this is amazing ! I will certainly try the other 6x6 too using similar logic. The hints for the shifted and smashed sums are slightly greek to me but will chew on it for a while. Thanks a lot for the prompt response.

Steps for bottom left 6X6. After usual solving, you can mark R1C5 as X, and then mark three other Xs in the grid. Then you can find two 4s in the grid. It should be easy after that. Click on "Show" below if you want to check the image.

its usually offline, like from past few years.
I think things are not yet fixed, once everything is fixed, it will be announced on this site.

Edited by swaroop2011 2014-03-16 4:43 AM