The New Sudoku Players' Forum

[bat999]

(5=8) r2c1 - r2c9 = (8-2) r3c8 = (2-5) r9c8 = (5) r9c7 => - 5 r2c7

Got it.
If r2c1 is 5 then r2c7 is not 5.
If r2c1 is 8 then r2c9 is not 8 and r3c8 becomes the 8 in that box.
So r9c8 becomes the 2 in that column.
And r9c7 is 5 and r2c7 is not 5 again.
=> - 5 r2c7

And 46 pair eliminates the 4 from r3c7.

Latest pencilmarks.

Code: Select all

.-------------.----------------.-------------.
| 3  56  49 | 1   8    2   | 7   459  569    |
| 58 7   2  | 34  4569 569 | 46  13   13689  |
| 1  568 49 | 346 4569 7   | 25  2489 369    |
:-----------+--------------+----------------:
| 28 28  7  | 46  3    1   | 9   45   56     |
| 49 13  6  | 7   459  459 | 8   13   2      |
| 49 13  5  | 8   2    469 | 46  7    13     |
:-----------+--------------+----------------:
| 27 29  1  | 5   67   68  | 3   89   4      |
| 57 59  3  | 2   47   48  | 1   6    89     |
| 6  4   8  | 9   1    3   | 25  25   7      |
'-----------'--------------'---------------'

[Leren]

bat999 wrote: Latest pencilmarks.

Keep going - the 2 Stringed Kite is next.

Leren

[bat999]

... the 2 Stringed Kite is next.

Nope.
I've used Empty Rectangle in box 3 to do the same job.
Then found your swordfish at r13c3, r34c4, r134c8.

Latest pencilmarks.

Code: Select all

.-----------.--------------.--------------.
| 3  56  49 | 1   8    2   | 7   459  569 |
| 58 7   2  | 3   4569 569 | 46  1    689 |
| 1  568 49 | 46  569  7   | 25  2489 3   |
:-----------+--------------+--------------:
| 28 28  7  | 46  3    1   | 9   45   56  |
| 49 1   6  | 7   459  459 | 8   3    2   |
| 49 3   5  | 8   2    469 | 46  7    1   |
:-----------+--------------+--------------:
| 27 29  1  | 5   67   68  | 3   89   4   |
| 57 59  3  | 2   47   48  | 1   6    89  |
| 6  4   8  | 9   1    3   | 25  25   7   |
'-----------'--------------'--------------'

[Leren]

bat999 wrote: Latest pencilmarks.

You need to remove 4 from r2c4 from your PM before you proceed to the next move. That was the direct elimination of the ER or Kite.

Leren

[bat999]

... remove 4

It was a typo only in my forum post.
Fixed it now.

[bat999]

Hi
"(4) r2c7 = r2c5 - r8c5 = (4-8) r8c6 = r7c6 - r7c8 = (8) r3c8 -> - 4 r3c8"
I needed this.

It probably translates to this...
(4=6) r2c7
If r2c7 is 4 then r3c8 is not 4.
If r2c7 is 6 then r2c5 is 4, r8c5 is 7, r7c5 is 6, r7c6 is 8, r7c8 is 9 and r1c8 is not 9.
This creates a locked pair of 45's r14c8 and r2c7 is not 4 again.
-> - 4 r3c8

"(9=4) r3c3 - (4=6) r3c4 - r4c4 = r4c9 - r6c7 = r6c6 - (6=8) r7c6 - (8=9) r7c8 => - 9 r3c8"
Using this instead...
If r2c5 is not 4 then r3c4 is 4, r3c3 is 9 and r3c8 is not 9.
If r8c5 is not 4 then r7c5 is 6, r7c6 is 8, r7c8 is 9 and r3c8 is not 9 again.
=> - 9 r3c8


I'm trying to complete the puzzle myself now.
I'll use your moves if I get stuck again.

Latest pencilmarks.

Code: Select all

.-----------.--------------.--------------.
| 3  56  49 | 1   8    2   | 7   459  569 |
| 58 7   2  | 3   4569 569 | 46  1    689 |
| 1  568 49 | 46  569  7   | 25  28   3   |
:-----------+--------------+--------------:
| 28 28  7  | 46  3    1   | 9   45   56  |
| 49 1   6  | 7   459  459 | 8   3    2   |
| 49 3   5  | 8   2    469 | 46  7    1   |
:-----------+--------------+--------------:
| 27 29  1  | 5   67   68  | 3   89   4   |
| 57 59  3  | 2   47   48  | 1   6    89  |
| 6  4   8  | 9   1    3   | 25  25   7   |
'-----------'--------------'--------------'

[Leren]

bat999 wrote: I'll use your moves if I get stuck again.

I think you'll find only the last of my previously mentioned moves is required to solve the puzzle from where you are:

Code: Select all

*--------------------------------------------------------------------------------*
| 3      d56      49       | 1       8       2        | 7      c459    c569      |
|e58      7       2        | 3       4569    569      | 46      1       69-8     |
| 1       56-8    49       | 46      569     7        |b25     a28      3        |
|--------------------------+--------------------------+--------------------------|
| 28      28      7        | 46      3       1        | 9       45      56       |
| 49      1       6        | 7       459     459      | 8       3       2        |
| 49      3       5        | 8       2       469      | 46      7       1        |
|--------------------------+--------------------------+--------------------------|
| 27      29      1        | 5       67      68       | 3       89      4        |
| 57      59      3        | 2       47      48       | 1       6       89       |
| 6       4       8        | 9       1       3        | 25      25      7        |
*--------------------------------------------------------------------------------*

(8=2) r3c8 - (2=5) r3c7 - r1c89 = r1c2 - (5=8) r2c1 => - 8 r2c9, r3c2; lclste

Leren

[bat999]

I think you'll find only the last of my previously mentioned moves is required to solve the puzzle from where you are:

Code: Select all

*--------------------------------------------------------------------------------*
| 3      d56      49       | 1       8       2        | 7      c459    c569      |
|e58      7       2        | 3       4569    569      | 46      1       69-8     |
| 1       56-8    49       | 46      569     7        |b25     a28      3        |
|--------------------------+--------------------------+--------------------------|
| 28      28      7        | 46      3       1        | 9       45      56       |
| 49      1       6        | 7       459     459      | 8       3       2        |
| 49      3       5        | 8       2       469      | 46      7       1        |
|--------------------------+--------------------------+--------------------------|
| 27      29      1        | 5       67      68       | 3       89      4        |
| 57      59      3        | 2       47      48       | 1       6       89       |
| 6       4       8        | 9       1       3        | 25      25      7        |
*--------------------------------------------------------------------------------*

(8=2) r3c8 - (2=5) r3c7 - r1c89 = r1c2 - (5=8) r2c1 => - 8 r2c9, r3c2; lclste

Hi
I'm not accepting this without an explanation.
(What happens if r3c8 is not 8?)

[Leren]

If r3c8 is not 8 it s 2, r3c7 is not 2 so it is 5, r1c89 are both not 5, r1c2 is 5 (since there only three 5's in Row 1), r2c1 is not 5 so it is 8.

So summarizing, if r3c8 is not 8 then r2c1 is 8. You can reverse this argument to show that if r2c1 is not 8 then r3c8 is 8.

So at least one of r2c1 and r3c8 must be 8.

Since r2c9 and r3c2 can see both of these cells neither can be 8.

All these words are simply what the AIC notation (8=2) r3c8 - (2=5) r3c7 - r1c89 = r1c2 - (5=8) r2c1 => - 8 r2c9, r3c2 says.

Leren

[bat999]

... r1c89 are both not 5...

Got it.

[bat999]

Can put it to bed now.
Thanks.

HoDoKu_extreme_3150_6.jpg (30.79 KiB) Viewed 959 times

[Leren]

... r1c89 are both not 5...

Got it.

I'm not quite sure why you were not understanding this term until I explained the whole chain in words. Perhaps it's because there was no number in front of the cell co-ordinates.

In theory I could have written the AIC notation as : (8=2) r3c8 - (2=5) r3c7 - (5) r1c89 = (5) r1c2 - (5=8) r2c1, however there is a convention that you don't have to put a number in front of the cell co-ordinates unless it changes from the previous term, so I didn't put (5) in front of terms 3 and 4. This de-clutters the AIC notation a bit but may be confusing for beginners.

Notice also that the numbers are all written inside brackets. This is because the AIC is meant to be read from right to left as well as from left to right. When you do this the status of each term (True or False) is the opposite of what it is when you read it from the other direction - in other words the assumed status of the term depends on the context in which it is read. So, for example, if you were reading the chain from right to left the term (5) r1c89 = would mean (in words) "at least 1 of r1c8 and r1c9 must be True" whereas they were both False when the chain was read from left to right.

Hope this helps.

Leren