badly stuck on Sunday Times

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badly stuck on Sunday Times

Postby mjo1943 » Wed Feb 08, 2006 7:51 pm

original:
5, , , ,9, , , ,3,
,3, ,5, ,8, ,9, ,
,6, , , , , ,5, ,
1, , ,3, ,9, , ,7,
, , , ,4, , , , ,
2, , ,8, ,5, , ,1,
,2, , , , , ,7, ,
,9, ,6, ,3, ,8, ,
6, , , ,7, , , ,9,

stuck at:
5, [1478],[12478],[247],9,6,[12478],[124],3,
[47],3,[247],5,1,8,[2467]9,[246],
[89],6,[124789],[247],3,[247],[12478],5,[248],
1,[45],[456],3,2,9,[458],[46],7,
[389],[58],[35689],[17],4,[17],[23589],[236],[2568],
2,[47],[3479],8,6,5,[349],[34],1,
[38],2,[1345],9,8,[14],[1345],7,[456],
[47],9,[147],6,5,3,[124],8,[24],
6,[1458],[13458],[124],7,[124],[1345],[134],9,

any guidance would be appreciated.thanks. [/code]
mjo1943
 
Posts: 5
Joined: 13 March 2005

Postby TKiel » Wed Feb 08, 2006 7:59 pm

I believe the starting grid and initial candidate listing is as follows:
Code: Select all

 *-----------*
 |5..|.9.|..3|
 |.3.|5.8|.9.|
 |.6.|...|.5.|
 |---+---+---|
 |1..|3.9|..7|
 |...|.4.|...|
 |2..|8.5|..1|
 |---+---+---|
 |.2.|...|.7.|
 |.9.|6.3|.8.|
 |6..|.7.|..9|
 *-----------*
 
 *-----------------------------------------------------------------------------*
 | 5       1478    12478   | 1247    9       12467   | 124678  1246    3       |
 | 47      3       1247    | 5       126     8       | 12467   9       246     |
 | 4789    6       124789  | 1247    123     1247    | 12478   5       248     |
 |-------------------------+-------------------------+-------------------------|
 | 1       458     4568    | 3       26      9       | 24568   246     7       |
 | 3789    578     356789  | 127     4       1267    | 235689  236     2568    |
 | 2       47      34679   | 8       6       5       | 3469    346     1       |
 |-------------------------+-------------------------+-------------------------|
 | 348     2       13458   | 149     158     14      | 13456   7       456     |
 | 47      9       1457    | 6       125     3       | 1245    8       245     |
 | 6       1458    13458   | 124     7       124     | 12345   1234    9       |
 *-----------------------------------------------------------------------------*


Tracy
TKiel
 
Posts: 209
Joined: 05 January 2006

Postby TKiel » Wed Feb 08, 2006 8:07 pm

Your candidate list has not been updated to show the affects of the assignment of some of the cells in your grid. R7c1 shows (3,8) as possiblities, when r7c5 contains an 8.
TKiel
 
Posts: 209
Joined: 05 January 2006

Postby Carcul » Wed Feb 08, 2006 8:18 pm

Hi Mjo1943.

R7c1 should be "34": then the naked pair on column 1 eliminate the "4" from r7c1. You can also eliminate the "6" from r5c9. Next you have some locked candidates in box 9, and after that a X-Wing.

Regards, Carcul
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Carcul

Postby mjo1943 » Mon Feb 13, 2006 8:13 pm

thanks for that but an having problems understanding x wing.:(
mjo1943
 
Posts: 5
Joined: 13 March 2005

Postby TKiel » Mon Feb 13, 2006 9:42 pm

mjo1943,

An x-wing is a pattern. There must be two rows, each row must have only two cells with the candidate and those two cells must be in the same two columns. Since there are only two places in each row where that candidate can be, if one is true the other must be false. The following grid is not from your puzzle but it does contain an x-wing in 9.
Code: Select all
 
 *------------------------------------------------------------*
 | 47     249    1    | 8      5      3  | 6      247    249  |
 | 5      369    789  | 2      4      16 | 1789   378    19   |
 | 3468   2346   28   | 7      9      16 | 18     23458  1245 |
 |----------------------+------------------+------------------|
 | 9      7      3    | 1      2      8  | 5      46     46   |
 | 2      8      5    | 9      6      4  | 3      1      7    |
 | 16     16     4    | 5      3      7  | 2      9      8    |
 |--------------------+------------------+--------------------|
 | 3478   2349   2789 | 46     1      5  | 789    2678   269  |
 | 1478   1245   278  | 46     78     9  | 178    25678  3    |
 | 178    159    6    | 3      78     2  | 4      578    159  |
 *------------------------------------------------------------*

Row 1 has two cells and only two, with candidate 9, c2 and c9; row 9 has two cells, and only two, with candidate 9, c2 and c9. Two rows, two cells, two columns. If r1c2 is true, r1c9 & r9c2 must be false and r9c9 must be true. If r1c9 is true, r1c2 & r9c9 must be false and r9c2 must be true. Basically the shape is a rectangle. Imagine lines connecting opposite corners of the rectangle, like an X. The cells on the end of one of the lines is true and the other is false. If r1c2 is 9, that placement means that row 1 has a 9 and column 2 has a 9 and no other cells in either row 1 or column 2 can be 9. If r1c2 is 9, then we also know that r9c9 is 9 (opposite corners of the diagonal are the same). That placement means that row 9 has a 9 and column 9 has a 9 and no other cell in row 9 or column 9 can be a 9.

So what happens if we assign 9 to any other cell in column 2, lets say r2c2. The value 9 candidates disappear from the rest of the cells in column 2. Now the only cell for row 1 that can possibly be a 9 is r1c9 and the only cell in row 9 that can be a 9 is r9c9. If we assign r1c9 as 9 then row 9 has no cell that can possibly be 9, which we know can't be correct. Basically, once the conditions of the x-wing are met (two rows, two cells, two columns) the assignment of that value to any cell besides the four that make up the x-wing, means that one row or column will not have that value.

Once you find the x-wing, all other cells in the two column that contain the x-wing value, except for the four cells that make up the x-wing, can have that value excluded. You can also have an x-wing is columns and the exclusions then occur in the rows.

Tracy
TKiel
 
Posts: 209
Joined: 05 January 2006

sunday times puzzle

Postby mjo1943 » Wed Feb 15, 2006 6:38 pm

I have found the X wing -thank you Tracy- but am still stuck at:
5,[1478][2478],[247]9,6,[2478][124],3,
[47],3,[247],5,1,8,[2467],9,[246],
[89],6,[124789],[247],3,[24],[12478],5,[248],
1,[458],[4568],3,2,9,[458],[46],7,
[89],[58],[356789],1,4,7,[23589],[236],[258],
2,[47],[3479],8,6,5,[349],[34],1,
3,2,[45],9,8,1,[456],7,[456],
[47],9,[147],6,5,3,[124],8,[24],
6,[158],[58],[24],7,[24],,[35],[13],9,
and how do you get that layout that you used?
thanks again for the help (so far?) :?:
mjo1943
 
Posts: 5
Joined: 13 March 2005

Postby tarek » Wed Feb 15, 2006 6:53 pm

hi mjo1943,

from your pncilmarks, the next logical steps should be

Code: Select all
*--------------------------------------------------------------------------*
| 5       1478    2478   | 247     9       6      | 2478    124     3      |
| 47      3       247    | 5       1       8      | 2467    9       246    |
| 89      6       124789 | 247     3       24     | 12478   5       248    |
|------------------------+------------------------+------------------------|
| 1       458     4568   | 3       2       9      | 458     46      7      |
| 89      58      356789 | 1       4       7      | 23589   236     258    |
| 2       47      3479   | 8       6       5      | 349     34      1      |
|------------------------+------------------------+------------------------|
| 3       2       45     | 9       8       1      | 456     7       456    |
| 47      9       147    | 6       5       3      | 124     8       24     |
| 6       158     58     | 24      7       24     | 35      13      9      |
*--------------------------------------------------------------------------*
Eliminating 7 From r5c3 (Naked Single in Row 5)
*--------------------------------------------------------------------------*
| 5       1478    2478   | 247     9       6      | 2478    124     3      |
| 47      3       247    | 5       1       8      | 2467    9       246    |
|*89      6      -124789 | 247     3       24     |-12478   5      *248    |
|------------------------+------------------------+------------------------|
| 1       458     4568   | 3       2       9      | 458     46      7      |
|*89     -58     -35689  | 1       4       7      |-23589   236    *258    |
| 2       47      3479   | 8       6       5      | 349     34      1      |
|------------------------+------------------------+------------------------|
| 3       2       45     | 9       8       1      | 456     7       456    |
| 47      9       147    | 6       5       3      | 124     8       24     |
| 6       158     58     | 24      7       24     | 35      13      9      |
*--------------------------------------------------------------------------*
Eliminating 8 From r3c3 ( XWing in Columns 19)
Eliminating 8 From r3c7 ( XWing in Columns 19)
Eliminating 8 From r5c2 ( XWing in Columns 19)
Eliminating 8 From r5c3 ( XWing in Columns 19)
Eliminating 8 From r5c7 ( XWing in Columns 19)


Tarek
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