Sunday 16 October 2011

Puzzle #34: Frameless Sudoku

This is so far the only genre I have made, that have also been made by other people. I like to see them from other people. They will also have a different feel from when you made them yourself. Also more fun if you don't know exactly how the puzzle is set up.
It's not that uncommon for puzzle types that people like only to made by its developer though. If you only look at Naoki Inaba's website and then try to find the puzzle ideas he thought of somewhere else. Very few of those are found anywhere else.
This puzzle I wanted to see if I could make all triplets of given sums to be consecutive. It worked out nicely even though the opening is a bit tricky to figure out.

Rules for Sudoku

The numbers on the outside indicate the sum of the first digits encountered in that row or column from that side. The amount of digits can differ from sum to sum and can be only one digit.


  1. Nice grid, not easy ! I found that not only the opening was tricky.
    It's an interesting type of sudoku, often quite hard.

  2. I agree, they tend to be on the hard side. That is mostly because you can keep the solving path incredibly narrow. The further along you get in construction, the less specific the clues can be as you can make them depend on digits that are already placed. This leaves no openings but the one you put in at the start of your design.

  3. Are you saying this way of construction is generally used ,and not always? I dont know of any other design method than the one you wrote about.

  4. It's not really the point of design method. It's more about a feature of Sudoku. Most Sudoku types have a collapsing point, where the difficulty drops from the opening and it becomes a lot of fill work. Here you can avoid that more than most types.

  5. how can be the sum 4? than we shoud write 3;1;0; or 2;1;1.
    how can be the sum 30? than we should write 10;10;10...
    please explain me this, thank you.

    1. Hi.

      It's a Frameless Sudoku, not a Frame Sudoku. Opposed to the Frame Sudoku where the number outside is the sum from the first 3 digits, in this puzzle the number outside is the sum of the first N digits, where N can be any number from 1-9. So a 4 sum could be the sum of the first 1 digits and the first cell would be 4, or the sum could be the sum for the first 2 digits, ergo the first 2 cells would be 1,3 or 3,1. In the same way, the 30 sum can be the sum from first 4,5,6 or 7 digits.
      I hope that helps.