The New Sudoku Players' Forum

[ArkieTech]

Code: Select all

 *-----------*
 |.67|.32|.9.|
 |...|...|7..|
 |..9|.56|4..|
 |---+---+---|
 |..6|.2.|.1.|
 |7..|.6.|..3|
 |.5.|.7.|6..|
 |---+---+---|
 |..5|24.|9..|
 |..1|...|...|
 |.9.|31.|52.|
 *-----------*


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[Leren]

Code: Select all

*--------------------------------------------------------------*
| 58    6     7      | 4     3     2      | 1     9     58     |
| 2345  234  d23     | 19    8     19     | 7    c36    256    |
| 1238  1238  9      | 7     5     6      | 4     38    28     |
|--------------------+--------------------+--------------------|
| 9     4-3   6      | 5     2     34     | 8     1     7      |
| 7     148   48     | 189   6     149    | 2     5     3      |
| 1238  5    e23     | 18    7     13     | 6     4     9      |
|--------------------+--------------------+--------------------|
| 36   a37    5      | 2     4     8      | 9    b67    1      |
| 248   2478  1      | 6     9     5      | 3     78    48     |
| 468   9     48     | 3     1     7      | 5     2     468    |
*--------------------------------------------------------------*

XY Wing with transport : (3=7) r7c2 - (7=6) r7c8 - (6=3) r2c8 - r2c3 = (3) r6c3 => - 3 r4c2; stte

Leren

[SteveG48]

Code: Select all

 *------------------------------------------------------------*
 | 58     6     7     | 4     3     2     | 1     9     58    |
 | 245-3 c234  a23    | 19    8     19    | 7     6-3   256   |
 | 1238   1238  9     | 7     5     6     | 4     38    28    |
 *--------------------+-------------------+-------------------|
 | 9     b34    6     | 5     2     34    | 8     1     7     |
 | 7      148   48    | 189   6     149   | 2     5     3     |
 | 1238   5    b23    | 18    7     13    | 6     4     9     |
 *--------------------+-------------------+-------------------|
 | 36     37    5     | 2     4     8     | 9     67    1     |
 | 248    2478  1     | 6     9     5     | 3     78    48    |
 | 468    9     48    | 3     1     7     | 5     2     468   |
 *------------------------------------------------------------*


(3=2*)r2c3 - (2=4)r4c2,r6c3 - (4*2=3)r2c2 => -3 r2c18 ; stte

Alternately:

(3)r2c2 = {XY-wing 2,3,4 r24c2,r6c3} - (2=3)r2c3 => -3 r2c18

[Ngisa]

Code: Select all

+---------------+-----------+----------+
| i58   6    7   | 4   3 2   | 1 9  58  |
| 2345 234  234 | 19  8 19  | 7 36 256 |
| h1238 h1238 9   | 7   5 6   | 4 g38 28  |
+---------------+-----------+----------+
| 9    c34   6   | 5   2 b34  | 8 1  7   |
| 7    k148  k48  | l189 6 4-19 | 2 5  3   |
| j1238 5    23  | m8-1  7 a13  | 6 4  9   |
+---------------+-----------+----------+
| 36   d37   5   | 2   4 8   | 9 e67 1   |
| 248  2478 1   | 6   9 5   | 3 f78 48  |
| 468  9    48  | 3   1 7   | 5 2  468 |
+---------------+-----------+----------+


(1=3)R6c6-r4c6=r4c2-(3=7)r7c2-r7c8=r8c8-(7=8)r3c8-r3c13=r1c1-r6c1=r5c23-r5c4=(8-1)r6c4=(1-8)r5c4=UR19r25c46 => -19r5c6; stte.

[SteveG48]

Code: Select all

+---------------+-----------+----------+
| i58   6    7   | 4   3 2   | 1 9  58  |
| 2345 234  234 | 19  8 19  | 7 36 256 |
| h1238 h1238 9   | 7   5 6   | 4 g38 28  |
+---------------+-----------+----------+
| 9    c34   6   | 5   2 b34  | 8 1  7   |
| 7    k148  k48  | l189 6 4-19 | 2 5  3   |
| j1238 5    23  | m8-1  7 a13  | 6 4  9   |
+---------------+-----------+----------+
| 36   d37   5   | 2   4 8   | 9 e67 1   |
| 248  2478 1   | 6   9 5   | 3 f78 48  |
| 468  9    48  | 3   1 7   | 5 2  468 |
+---------------+-----------+----------+


(1=3)R6c6-r4c6=r4c2-(3=7)r7c2-r7c8=r8c8-(7=8)r3c8-r3c13=r1c1-r6c1=r5c23-r5c4=(8-1)r6c4=(1-8)r5c4=UR19r25c46 => -19r5c6; stte.

Ngisa, I don't see a candidate 7 at r3c8.

[Ngisa]

Code: Select all

+---------------+-----------+----------+
| i58   6    7   | 4   3 2   | 1 9  58  |
| 2345 234  234 | 19  8 19  | 7 36 256 |
| h1238 h1238 9   | 7   5 6   | 4 g38 28  |
+---------------+-----------+----------+
| 9    c34   6   | 5   2 b34  | 8 1  7   |
| 7    148  48  | l19-(8) 6 4-(19) | 2 5  3   |
| j1238 5    23  | k8-(1)  7 a13  | 6 4  9   |
+---------------+-----------+----------+
| 36   d37   5   | 2   4 8   | 9 e67 1   |
| 248  2478 1   | 6   9 5   | 3 f78 48  |
| 468  9    48  | 3   1 7   | 5 2  468 |
+---------------+-----------+----------+


(1=3)R6c6-r4c6=r4c2-(3=7)r7c2-r7c8=r8c8-(7=8)r3c8-r3c13=r1c1-r6c1=r5c23-r5c4=(8-1)r6c4=(1-8)r5c4=UR19r25c46 => -19r5c6; stte.

Ngisa, I don't see a candidate 7 at r3c8.

Steve you are quite right
The proper chain should be
(1=3)r6c6-r4c6=r4c2-(3=7)r7c2-r7c8=(7-8)r8c8=(8)r3c8-r3c12=r1c1-r1c6=r6c4-r5c4=UR1/9r25c46 =>-19r5c6; stte.

[SteveG48]

Code: Select all

+---------------+-----------+----------+
| i58   6    7   | 4   3 2   | 1 9  58  |
| 2345 234  234 | 19  8 19  | 7 36 256 |
| h1238 h1238 9   | 7   5 6   | 4 g38 28  |
+---------------+-----------+----------+
| 9    c34   6   | 5   2 b34  | 8 1  7   |
| 7    148  48  | l19-(8) 6 4-(19) | 2 5  3   |
| j1238 5    23  | k8-(1)  7 a13  | 6 4  9   |
+---------------+-----------+----------+
| 36   d37   5   | 2   4 8   | 9 e67 1   |
| 248  2478 1   | 6   9 5   | 3 f78 48  |
| 468  9    48  | 3   1 7   | 5 2  468 |
+---------------+-----------+----------+


(1=3)R6c6-r4c6=r4c2-(3=7)r7c2-r7c8=r8c8-(7=8)r3c8-r3c13=r1c1-r6c1=r5c23-r5c4=(8-1)r6c4=(1-8)r5c4=UR19r25c46 => -19r5c6; stte.

Ngisa, I don't see a candidate 7 at r3c8.

Steve you are quite right
The proper chain should be
(1=3)r6c6-r4c6=r4c2-(3=7)r7c2-r7c8=(7-8)r8c8=(8)r3c8-r3c12=r1c1-r1c6=r6c4-r5c4=UR1/9r25c46 =>-19r5c6; stte.

Thanks, I should have seen that. However, I still don't follow your conclusion. The UR makes r5c6=4 if r6c6 <> 1; i.e., (1)r6c6 = (4)r5c6. From this we can conclude that r5c6 <> 1. In fact, the rules of URs (I don't remember which one) tell us that neither r5c4 or r5c6 can be a 1, even without the logic chain, but I don't see how we get r5c6 <> 9.

[Ngisa]

Steve
Do you agree that r6c4 cannot be 1? because when r6c6 is set to 3, r6c4 turns out to be 8, so, it cannot be 1.when r6c4 is 8, 8 cannot be in r5c4, so, it turns out the UR to be a type 1 (instead of type 4 which does not solve it), so 19 must be removed from r5c6, otherwise you will have DP.
I do not know whether this makes it clear.

[SteveG48]

Steve
Do you agree that r6c4 cannot be 1? because when r6c6 is set to 3, r6c4 turns out to be 8, so, it cannot be 1.when r6c4 is 8, 8 cannot be in r5c4, so, it turns out the UR to be a type 1 (instead of type 4 which does not solve it), so 19 must be removed from r5c6, otherwise you will have DP.
I do not know whether this makes it clear.

OK, I've got it now. If r6c6 is a 3 then r5c5 must be a 4. I got that from the beginning. What I didn't see was how you were getting there if r6c6 was a 1. I see now that that would make r2c6 a 9, again eliminating both 1 and 9 from r5c6. Good stuff!