## Stumped by a Very Hard puzzle

Post the puzzle or solving technique that's causing you trouble and someone will help

### Stumped by a Very Hard puzzle

Hi,
Okay, I can solve this by branching but know there must be
*logic* to solve this I'm missing. I have always been able to solve
hard and v.hard puzzles until this one. I've stared at it a while and it's
driving me nuts. Please show me the next step (what box/pencilmark
you'd eliminate and why) - I'm sure I can take it from there.
Thanks!

Original puzzle:
Code: Select all
`- 4 -   - - -    - 6 -1 - -   8 - 7    - - 2- - 7   - 6 -    8 - -- 6 -   1 - 9    - 4 -- - 2   - - -    9 - - - 1 -   5 - 3    - 2 -- - 1   - 5 -    2 - -2 - -   7 - 6    - - 5- 5 -   - - -    - 9 -`

I am able to get it to this point:
Code: Select all
`3589      4      3589         239     139     125         137       6       1379  1       39       6           8      349      7          345     35         2359       2        7          349       6      15         8       13        13493578      6        358         1        2      9         357       4         37834578    378       2           6      478     48          9      13578      13784789      1        489         5      478      3          67        2        678346789   3789      1          349     5      48           2        378       34678   2      389    3489         7     13489     6          134       138         534678      5      348         234    1348     12        13467      9         134678`
luvsudoku

Posts: 10
Joined: 29 January 2006

### Re: Stumped by a Very Hard puzzle

luvsudoku wrote:Hi,
Okay, I can solve this by branching but know there must be
*logic* to solve this I'm missing. I have always been able to solve
hard and v.hard puzzles until this one. I've stared at it a while and it's
driving me nuts. Please show me the next step (what box/pencilmark
you'd eliminate and why) - I'm sure I can take it from there.
Thanks!

Original puzzle:
Code: Select all
`- 4 -   - - -    - 6 -1 - -   8 - 7    - - 2- - 7   - 6 -    8 - -- 6 -   1 - 9    - 4 -- - 2   - - -    9 - - - 1 -   5 - 3    - 2 -- - 1   - 5 -    2 - -2 - -   7 - 6    - - 5- 5 -   - - -    - 9 -`

I am able to get it to this point:
Code: Select all
`----------------------+--------------------+----------------------| 3589   4      3589   | 239   139    125   | 137    6      1379   | 1      39     6      | 8     349    7     | 345    35     2      | 359    2      7      | 349   6      15    | 8      13     1349   |----------------------+--------------------+----------------------| 3578   6      358    | 1     2      9     | 357    4      378    | 34578  378    2      | 6     478    48    | 9      13578  1378   | 4789   1     489     | 5     478    3     | 67     2      678    |----------------------+--------------------+----------------------| 346789 3789  1       | 349   5      48    | 2      378    34678  | 2      389   3489    | 7     13489  6     | 134    138    5      | 34678  5     348     | 234   1348   12    | 13467  9      134678 |----------------------+--------------------+----------------------|`

You have a X-Wing in 7 in r57c28 that allows for some elimination of candidates in row 5 & 7. this enables you to place 7 in Block 5.
Then you need to look for Locked Candidates in 8 in Block 4 and Block 7 to determine where 8 goes in Row 9. After this the puzzle solves with singles.

If you don't understand the techniques check HERE and HERE.
Crazy Girl

Posts: 189
Joined: 08 November 2005

### Thanks!

Thanks for the help and the links. I've been using these techniques (missed the 7 xwing though) and never knew they had names
luvsudoku

Posts: 10
Joined: 29 January 2006

There is also a swordfish in 7's that makes the same exclusions as the x-wing plus a few more. (r1c79, r4c179 and r9c179). Could there be a jellyfish too?

Tracy
TKiel

Posts: 209
Joined: 05 January 2006

I was only kidding when I mentioned a jellyfish in the post above, but it turns out there is one in 8's.

Tracy
TKiel

Posts: 209
Joined: 05 January 2006