Solver App for Android and iPhone
Strategies for Number Puzzles of all kinds
Page Index
Solvers
Puzzles
Basic Strategies
Tough Strategies
Diabolical Strategies
Extreme Strategies
Depreciated Strategies
Str8ts
Other

Sue-De-Coq

This exotic strategy is strongly related to trivial patterns like Naked Pairs and Naked Triples since we are identifying Locked Sets. The building blocks are Almost Locked Sets but the most interesting aspect is the alignment of these parts.

To re-cap the terns:
  • A Locked Set is a group of N cells that can see each other which have N candidates - an example being a Naked Pair
  • An Almost Locked Set is a group of N cells which are mutually visible and share N+1 candidates in some combination.
There is a sequence we can follow:
  • An Almost Almost Locked Set is a group of N cells which are mutually visible and share N+2 candidates in some combination.
  • An Almost Almost Almost Locked Set is a group of N cells which are mutually visible and share N+3 candidates in some combination.
and so on. Horrible names and often abbreviated AALS, AAALS etc.

Sue-De-Coq Example 1
Sue-De-Coq Example 1 : Load Example or : From the Start
Sue-De-Coq, named after the forum handle of the clever chap who identified it, starts with an AALS which must be aligned in a row or column AND be wholly contained within a box. This restricts the size of the AALS group to two or three cells.

In the first example the two yellow cells (N=2) contain {2,3,5,8} which is N+2, or four candidates. The group is contained within box 4. We don't know which of the values {2,3,5,8} will be the solution to D2 and E2 but clearly two of those four will be. Now, if we look along the unit of alignment (column 2) and within the box we can find single cells that contain two of those candidates. B2 contains {2,8} (the green cell) and F3 contains {3,5}. The AALS can see these cells - which is important!

We now know that the solution to the AALS {D2,E2} cannot be 2/8 or 3/5 since it would leave nothing in the cells B2 and F3.
The logic is as follows. If neither {2/8} can fill the AALS nor {3,5} then some other combination must fill it that leaves a digit free for the single bi-value cells. So effectively {2,3,5,8} must fill all coloured cells. Indeed the group in total contains four cells and there are four candidates, so we have identified the total group as a Locked Set. This means we can remove all candidates X that see all X in the total group. This excludes the 8 in C2 and J2 (aligned in the column) and 2 G2 (also aligned in the columns) and the 3 in E3 (shares the box).

Sue-De-Coq Example 2
Sue-De-Coq Example 2 : Load Example or : From the Start
The example above was a relatively easy pattern - we found a four cell Locked Set. Sue-De-Coq can be used in more complicated patterns like the second example. In the first example we used bi-value single cells as the 'hooks' to make the 4-cell locked sets. Bi-value cells are by definition Almost Locked Sets since they contain two candidates in one cell. Sue-De-Coq can use larger ALSs to make the pattern.

In the second example we combine an AAALS (N+3) in {E7,E8} containing {1,3,6,7,8} with two normal ALSs {D9,F9} and {E2} containing {1,3,7} and {6/8} respectively. The trick is that the total number of cells, 5, equals the total number of candidates in all the cells {1,3,6,7,8}. We get a 5-cell Locked Set.
To eliminate we look at what candidates OUTSIDE the pattern can see ALL the candidates INSIDE the pattern. These are the 6s and 8s in row E, and the 1s, 3s and 7s in box 6.

Generally then...

The general terms the rule for the pattern is as follows:
  1. Find a 2-cell or 3-cell group inside a box that is also aligned on a row or column - call it group C
  2. C contains a set of candidates, V, which must be two or more than the number of cells in C (N+2, N+3 ALS etc).
  3. We need to find at least one bi-value cell (or larger ALS) in the row or column which only contains candidates from set V, called D
  4. We need to find at least one bi-value cell (or larger ALS) in the box which only contains candidates from set V, called E
  5. The candidates in D and E must be different.
  6. Remove any candidates common to C+D not in the cells covered by C or D in the row or column
  7. Remove any candidates common to C+E not in the cells covered by C or E in the box

Go back to Empty RectanglesContinue to Death Blossom


Comments

Your Name/Handle

Email Address - required for confirmation (it will not be displayed here)

Your comment or question

Please enter the
letters you see:
arrow
Enter these letters Remember me


Please keep your comments relevant to this article.
Email addresses are never displayed, but they are required to confirm your comments. When you enter your name and email address, you'll be sent a link to confirm your comment. Line breaks and paragraphs are automatically converted - no need to use <p> or <br> tags.
Talk Subject Comments
Comments here pertain to corrections to the text, not the subject itself
Article created on 12-April-2008. Views: 56419
This page was last modified on 5-April-2010.
All text is copyright and for personal use only but may be reproduced with the permission of the author.
Copyright Andrew Stuart @ Syndicated Puzzles Inc, 2011