Stuck on last grid

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Stuck on last grid

Postby enxio27 » Mon Oct 09, 2017 8:34 pm

This is the final grid in Ruud's Clueless Sumo X (full puzzle here: http://i.imgur.com/Ubu0fa9.png). I've solved all the rest of the puzzle, but I'm stuck on G1:

Code: Select all
.-------------------------------.-------------------------------.-------------------------------.
| 27        3         189       | 6         5         28        | 2789      127       4         |
| 18        24        5         | 249       49        7         | 3         6         18        |
| 6         89        47        | 1         34        238       | 27        257       59        |
:-------------------------------+-------------------------------+-------------------------------:
| 4         6         3         | 5         2         9         | 78        17        18        |
| 5         1         29        | 7         8         4         | 29        3         6         |
| 289       7         289       | 3         6         1         | 4         25        59        |
:-------------------------------+-------------------------------+-------------------------------:
| 2389      289       12        | 29        139       5         | 6         4         7         |
| 37        5         467       | 8         347       36        | 1         9         2         |
| 127       249       467       | 249       1479      26        | 5         8         3         |
'-------------------------------.-------------------------------.-------------------------------'


Richard Broughton's SudokuSolver suggests an X-Cycle as the next step, but I don't know what that is--haven't even heard of it before. Ruud was always very conscientious to make all grids of a multi-grid puzzle of similar difficulty, so I find it hard to believe that I'm having this much difficulty with this one grid.
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Re: Stuck on last grid

Postby Leren » Mon Oct 09, 2017 11:17 pm

I put your puzzle into Andrew Stuart's Sudoku X solver, which you can find here.

The move it makes is an XWing in 4's as in the following PM

Code: Select all
.-------------------------------.-------------------------------.-------------------------------.
| 27        3         189       | 6         5         28        | 2789      127       4         |
| 18        24        5         | 249       9-4       7         | 3         6         18        |
| 6         89       *47        | 1        *34        238       | 27        257       59        |
:-------------------------------+-------------------------------+-------------------------------:
| 4         6         3         | 5         2         9         | 78        17        18        |
| 5         1         29        | 7         8         4         | 29        3         6         |
| 289       7         289       | 3         6         1         | 4         25        59        |
:-------------------------------+-------------------------------+-------------------------------:
| 2389      289       12        | 29        139       5         | 6         4         7         |
| 37        5        *467       | 8        *347       36        | 1         9         2         |
| 127       249       67-4      | 249       179-4     26        | 5         8         3         |
'-------------------------------.-------------------------------.-------------------------------'

The next move is another XWing as in the following PM

Code: Select all
.-------------------------------.-------------------------------.-------------------------------.
| 27        3         189       | 6         5         28        | 2789      127       4         |
| 18       *24        5         |*24        9         7         | 3         6         18        |
| 6         89        47        | 1         34        238       | 27        257       59        |
:-------------------------------+-------------------------------+-------------------------------:
| 4         6         3         | 5         2         9         | 78        17        18        |
| 5         1         29        | 7         8         4         | 29        3         6         |
| 289       7         289       | 3         6         1         | 4         25        59        |
:-------------------------------+-------------------------------+-------------------------------:
| 389-2    *289       1-2       |*29        13        5         | 6         4         7         |
| 37        5         467       | 8         347       36        | 1         9         2         |
| 127       249       67        | 249       17        26        | 5         8         3         |
'-------------------------------.-------------------------------.-------------------------------'

After that the puzzle solves in singles. The puzzle solution in line format is 239658714145297368687143259463529871512784936978361425821935647354876192796412583

I suggest that you use Andrew's site in future, I doubt that there is much interest in Sudoku X on this site.

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Re: Stuck on last grid

Postby enxio27 » Tue Oct 10, 2017 12:08 am

Got it, thanks! I've never seen an X-wing referred to as an X-cycle. Is that some new terminology? I've never seen it before, even in Richard Broughton's SudokuSolver program.

I've also never seen that site you linked to. I guess a few things have changed in the past year.

As for this forum, it's one of only two Sudoku forums left (that I'm aware of, the other being Richard Broughton's SudokuSolver forum).
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Re: Stuck on last grid

Postby Leren » Tue Oct 10, 2017 2:03 am

Andrew Stuart's site has been around for many years and covers several Sudoku variants, as well as other puzzle games.

Some other sources of Sudoku information/discussion are Hodoku here and Systematic Sudoku here.

I just found a reference to X Cycles on Andrew's site here. As I suspected it means a single digit closed loop of any length, an X Wing being a simple example.

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Re: Stuck on last grid

Postby enxio27 » Tue Oct 10, 2017 4:22 pm

Interesting links, but no forums that I can see. I'll have to read more about the X-cycles.
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Re: Stuck on last grid

Postby tarek » Tue Oct 10, 2017 11:19 pm

Your quest needs an x-wing ....
Focus on the 4s now. There may be another x wing in lurking around the corner later

tarek

[Edit: oops Just noted that somebody else gave out the entire solution already]
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