Friday, 30 May 2014

Daily League Sudoku #42: Hit Sudoku

Last weekend was the Japanese NumberPlace Championship. It was full of great puzzles, but my favourite was the Hit NumberPlace by Naoki Inaba. I didn't manage to solve it during the championship as I didn't find the logic. But once I found the logic afterwards I really enjoyed it. That's why I decided to write one of my own for the league.

During the solve I realised a bit of logic that I thought would be fun to use in one of these puzzles. I just had to find a nice solution grid in which I could easily implement this. I actually stole a solution grid from the JNPC, which I slightly altered as at one point during construction I ran into no solution. But I noticed that by switching a few numbers around it could still have a solution. The trick I used isn't overly hard but I think it might be wise to try to solve the original puzzle first so that you can understand the logic involved, because I think it is useful to understand the genre before attempting this puzzle. The hit NumberPlace is #19 in the set.

That said, the puzzle is completely logically solvable. I think it is nice but it a bit on the harder side. Still, I hope you'll enjoy it.

Rules for Sudoku

Numbers outside the original grid indicate how many digits are the same in the solution grid in the corresponding row or column.

Click to enlarge

Friday, 16 May 2014

Daily League Sudoku #41: Pusula

I haven't written any Sudokus in a while. Now that Tom Collyer is taking a break to focus all his attention on the upcoming World Sudoku Championships in the UK, I'm taking over the Friday together with Zoltan Horvath. We'll probably be alternating weeks, so that we both get our fair share of puzzles in.

I got this type off Serkan Yurekli's blog. I was browsing it for an example of a puzzle type and came across it. I thought it would be a nice idea for the Daily League. I hadn't ever made one. It wasn't too hard to write this type. I think in general many grids will allow a unique solution, but there's a few restrictions to the solution to make that viable. I wrote this one progressively and added the missing arrows in the end. I don't think it's necessary to follow the intended solving path as there's a general strategy to this puzzles that should also always work to solve them. I hope it's enjoyable. It shouldn't be overly hard as some of my other Sudokus have been.

Rules for Sudoku

In this Sudoku an arrow in a cell with an even digit points to the largest odd orthogonal neighbour of that cell. An arrow in a cell with an odd digit points to the largest even orthogonal neighbour of that cell. All arrows have been given.