dailysudoku.com Forum Index dailysudoku.com
Discussion of Daily Sudoku puzzles
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

A Uniqueness Elimination

 
Post new topic   Reply to topic    dailysudoku.com Forum Index -> Solving techniques, and terminology
View previous topic :: View next topic  
Author Message
keith



Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA

PostPosted: Sun Jul 15, 2007 12:12 pm    Post subject: A Uniqueness Elimination Reply with quote

Here is one I thought interesting. It is a Brain Basher's Super Hard:
Code:

Puzzle: BB070307sh
+-------+-------+-------+
| . . . | 4 . 5 | . . . |
| . 8 . | 9 . 2 | . 4 . |
| . 4 2 | . 8 . | 5 9 . |
+-------+-------+-------+
| 2 9 . | . . . | . 7 3 |
| . . 4 | . . . | 9 . . |
| 5 3 . | . . . | . 6 2 |
+-------+-------+-------+
| . 2 9 | . 4 . | 7 3 . |
| . 5 . | 7 . 3 | . 8 . |
| . . . | 1 . 9 | . . . |
+-------+-------+-------+

Basic methods get you to here:
Code:
+-------------------+-------------------+-------------------+
| 9     16    1367  | 4     167   5     | 12368 12    1678  |
| 1367  8     5     | 9     167   2     | 136   4     167   |
| 167   4     2     | 3     8     16    | 5     9     167   |
+-------------------+-------------------+-------------------+
| 2     9     168   | 56    156   146   | 148   7     3     |
| 1678  16    4     | 2     3     167   | 9     15    158   |
| 5     3     17    | 8     9     147   | 14    6     2     |
+-------------------+-------------------+-------------------+
| 16    2     9     | 56    4     8     | 7     3     156   |
| 4     5     16    | 7     26    3     | 126   8     9     |
| 38    7     38    | 1     256   9     | 26    25    4     |
+-------------------+-------------------+-------------------+

You can continue with an X-wing, etc., but the solution still has a number of steps.

Or, notice the <26> UR in R89C57. To avoid the deadly pattern, either R8C7 is <1>, and/or R9C5 is <5>.

Looking in R9 and B9, if R9C5 is <5>, R8C7 is <1>. Thus, R8C7 must be <1>, and the puzzle is solved.

Keith
Back to top
View user's profile Send private message
Johan



Joined: 25 Jun 2007
Posts: 206
Location: Bornem Belgium

PostPosted: Thu Sep 27, 2007 2:58 pm    Post subject: Reply with quote

This UR elimination comes from the recent VH from 26 Sept

For avoiding the deadly [15] pattern in R29C12

a) R2C1 must contain a <6>, <7>, or a <9>

OR

b) R2C2 must contain a <6> or a <7>

In both ways it results in a naked [679] triple in the first four cells in R2, which erases the <6> in R2C9, though it didn't crack the puzzle, i found it a rather nice step.

Code:

+-----------------+----------------+-------------+
| 1235679 8    23 | 3679 13679 137 | 4  1569 156 |
|*15679  *1567 69 | 679  8     4   | 3  2   15-6 |
| 1369    136  4  | 5    1369  2   | 7  169  8   |
+-----------------+----------------+-------------+
| 39      2    5  | 8    39    6   | 1  47   47  |
| 8       4    69 | 279  1279  157 | 26 56   3   |
| 367     367  1  | 4    23    35  | 9  8    256 |
+-----------------+----------------+-------------+
| 4       36   8  | 1    236   9   | 5  67   267 |
| 236     9    23 | 367  5     37  | 8  14   14  |
|*15     *15   7  | 26   4     8   | 26 3    9   |
+-----------------+----------------+-------------+
Back to top
View user's profile Send private message Send e-mail
Display posts from previous:   
Post new topic   Reply to topic    dailysudoku.com Forum Index -> Solving techniques, and terminology All times are GMT
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group