Dr. Sudoku Prescribes #106 – Star Battle
or solve online (using our beta test of Penpa-Edit tools)
Theme: Honeycomb
Rules: Standard Star Battle rules. Two stars per row, column, and region.
Answer String: For each row from top to bottom, enter the number of the first column from the left where a star appears. Enter these numbers as a single string with no separators.
Time Standards (highlight to view): Grandmaster = 3:15, Master = 6:00, Expert = 12:00
Solution: PDF
Note: Follow this link for other classic Star Battles and this link for Star Battle variations. If you are new to this puzzle type, here are our easiest Star Battles to get started on. More Star Battle puzzles can be found in The Art of Puzzles, in the book Star Battle by JinHoo Ahn, and in our beginner-friendly collection Intro to GMPuzzles by Serkan Yürekli.
4:00. Certainly one of the most enjoyable star battle solves.
The Y room in bottom-left made it easier to work with the six identical rooms.
I’ve gotten star battle lessons before but I think I still need some more. This took me a long time and felt like I had to do a lot of lookahead instead of finding logical reasons for things, more like I was searching a tree of possibilities instead of finding a path.
This uses the particular kind of logic “if a star goes here then another star must go there but this is a problem” a whole lot.
Particularly in the honeycomb you’ll find spots close to neighboring regions that do immediate pushes. But in some rows adding two more stars for this kind of reason now gets you to three stars. The intended solving path is along the right, then the top down, using this brand of logic a fair bit.
For instance, can a star go in R4C4? Well, this forces another star in R4C6 but now three total stars with R4C8. So instead nothing is in R4C4 and a star is in R3C34 instead.
Thanks for the pointers. I used that kind of logic a lot, and I see immediately how to get from R4C4 to R4C6 but then it takes a lot more thought for me to get to R4C8, the kind of amount where I’ll need to actually draw some kind of temporary-guess stars in those first two cells (and probably notice a ton of irrelevant stuff that they imply) before I spot the problem. So this is roughly the kind of solution path I used, only I did it way too inefficiently.
Time for some more practice!
Well, R4C8 should already be filled in as a sure star when you are considering the above. So I’m wondering if you missed something much earlier (and easier) in just the rightmost columns that sets up the rest of the puzzle.
Ah, indeed, I got to looking at that (in hindsight obvious) thing way later in my solve so I didn’t see how much it would have done for me if only I had seen it sooner. I looked at total number of stars in some larger groups of rows and columns, as I generally would for “ins and outs” like in an irregular sudoku, but didn’t start my search with 1 column! Thanks for that reminder too.
22mins.