Saturday, 30 November 2013

Daily League Sudoku #36: Sum Relations Sudoku

I have seen puzzles similar to this before, except in a Killer Sudoku format. In those puzzles the relations are given between different cages. Here the relation is between the sums of adjacent cells on either side of the symbol.
This is again a harder puzzle. I don't know exactly how hard it is, but there's definitely no progress to be made if you don't understand the opening. I wasn't expecting to be able to make this variant without any givens. But I managed to create an opening that works without any givens. I think it's a nice and interesting opening. The middle is probably a bit easier, but I think the end is again a little bit harder, but worked out nicely in my opinion. I'll think about making something easier again next week, but I can't exactly promise that. When I find an interesting opening, I just run with it. And interesting is generally hard. Enjoy this puzzle though.

In this Sudoku, the symbols indicate the relation between the sums of the 2 cells on either side of the symbol.

Saturday, 23 November 2013

Daily League Sudoku #35: Rank Killer Sudoku

This week a puzzle type taken from Richard Stolk's V2V test at Logicmasters India. I had planned on posting this type earlier, but my attempts at making one never got anything useful. So I made other puzzle types instead, that worked out easier. But this one seemed to work well.
This puzzle is again a harder one. I had posted a few easier ones in the last few weeks. This type has again some room for me to be a bit more creative with the opening. There's a few steps that combine Killer Sudoku and Rank Sudoku to start this one off. They are still all logical steps, but it takes a bit more effort to figure them out. I still think it is an enjoyable puzzle.

As a reminder all Daily League puzzles are also solvable at SudokuCup.

Rules for Sudoku

The sum of digits inside each dashed cage is given at the upper left cell of the cage. A digit 'N' in a circle means that the digit in the cell is the Nth smallest number in the corresponding cage. Digits cannot repeat within a cage.

Click to enlarge

Saturday, 16 November 2013

Daily League #34: Arrow Sudoku

This week a more familiar variant. Arrow Sudoku has been around for a while now and there's been many nice puzzles made. I hope this one is also enjoyable.
I decided to go for a similar layout as my Renban Sudoku I made a while back for the league. I thought it would work well with Arrow Sudoku too. I was able to give fewer givens though as the arrow already forces some placement because of the direction. I shortly considered making a directionless Arrow Sudoku, where the circle could be at either end, but this layout wasn't very friendly for that variant. At first I had a harder variant of this Sudoku, but it took me too long to solve it myself while knowing the openings because the middle and end ran a lot on very complex interactions between the arrows that I really couldn't justify logically. So I revamped it a little to make it more solvable. The harder opening is still in this puzzle but it is no longer needed to solve the puzzle as there's a more friendly path through the puzzle.

Rules for Sudoku

In this Sudoku a number of arrows are given with a circle at the end. The digit in a circle is equal to the sum of the digits along its arrow. Digits may repeat along an arrow as long as they don't break any Sudoku rules.

Saturday, 9 November 2013

Daily League Sudoku #33: Hi-Lo Product Frame Sudoku

This week another variation on the Hi-Lo Frame Sudoku. It's a fun variant you can always play around with. This time it's products instead of sums. It leaves for fewer options and thus allows fewer clues.
Outside clues and empty grids are always my favourite Sudokus to construct. It's generally a bit of a struggle to get them to turn out unique or even create an opening. This one was a bit of a struggle to get unique as my final clue had to settle about 35 cells. There were a few options that got pretty close but would end up having no solution. This was the only one I could find that settled the uniqueness issue. There was a second option that I thought had worked, but then I realised the clue didn't actually have to be in that configuration and thus there were many more solutions. The puzzle itself is not overly hard as the clues give you a lot of information from the start and the clue I used for uniqueness is already helpful far earlier than it was in my construction.

Rules for Sudoku

In this Sudoku, the numbers on the outside indicate the product of the highest and lowest digit in the first three cells of that row or column when looking from that side.

Daily League Sudoku #32: N-Sums Sudoku and Quad Max Difference Sudoku

This post is just preceding this week's Sudoku. I hadn't made blogposts of my previous 2 Sudoku. The first one was made en route to Beijing for the WSC/WPC. I had no access to Facebook or BlogSpot there, so I wasn't able to make any posts. The second one I was not at home and managed to sneak in some time to make a quick Facebook post with the image, which all is a little bit faster than making posts on my blog.
The first puzzle is a variant on the X-Sums Sudoku, of which I have made a few. The variant is a bit more limiting as now not every row and column necessarily has a valid clue. This is caused by the fact that a number N has to appear in position N to become a valid clue. The construction took a while as I wanted to keep the symmetric layout and sometimes I wasn't able to make the layout symmetric as there was no longer a clue available. There are a few clues that aren't necessary for uniqueness in this puzzle, but they don't hinder the solving path and make it overall a little bit easier. I think people don't mind that my Sudokus are made a bit easier in general.
The second puzzle is a simple variant with differences. It has more given numbers than I would have wanted, but it wouldn't be unique otherwise. I wanted to make a puzzle which had a single instance of every possible Quad Difference clue possible. This of course forced one of the clues to be in a specific position as otherwise there's be no unique solution available. Which is why I went for this layout. I don't think this one is overly hard. There's a few key points in the solve where you have to use the right clues.

Rules for Sudoku

N-Sums Sudoku:
Clues outside the grid indicate the sum of the first N digits seen in that row or column from that side. The digit N is always indicated by the Nth digit seen from that side. In other words, it is always the last digit in the summed set of digits.

Quad Max Difference Sudoku:
In this Sudoku, numbers on grid points indicate the maximum difference between the four digits surrounding it. Each difference must appear at least once around each clue.