dailysudoku.com

nataraj · Last edited by nataraj on Tue Aug 05, 2008 8:22 pm; edited 1 time in total

I did some reading, both here and in the sudoku player's forum but could not find a mention of this UR elimination. It does appear however in a post by ravel on Thu Jun 19, 2008 in the "ending proves challenging" thread.

wapati · Posted: Wed Jul 30, 2008 8:31 pm Post subject:

Scanraid call it a hidden UR type 2.

http://www.scanraid.com/Hidden_Unique_Rectangles

Jean-Christophe, author of jsudoku, calls it a hidden UR.

Smile

tlanglet · Posted: Fri Aug 01, 2008 11:09 pm Post subject:

Nataraj,

I recently had a similar question on a Type 2 UR here

At my current stage of understanding, I just accept these very specific circumstances as variations on the basic type.

Ted

nataraj · Posted: Sun Aug 03, 2008 5:21 pm Post subject:

Thank you wapati and Ted!

Seems I must wait and see what other nomenclature will evolve over time.

Right now I am not happy with either "hidden type 2" or "type 2 ..." whatever. The situation is no type 2 at all here: x and y can be different and/or represent any number of additional candidates, while "type 2" in my book covers the very special case when both top cells have exactly 3 candidates and the extra candidate the same in both top cells. Maybe Andrew Stuart means "hidden UR type 2" in the sense that there are two types of hidden URs. Myself I do not like the notion of "hidden" UR - what kind of other UR is there?

Be that as it may, I'll just have to call these babies "UR ab r12c15 plus strong link on a in row 1" ... That is just as well, since usually the shorthand descriptions require more specific attributes anyway, think of "W-wing 18 with strong link on 8 in row 3", "kite (2) in row 4 and col 9".

Thanks again!

tlanglet · Posted: Sun Aug 03, 2008 6:15 pm Post subject:

nataraj · Posted: Tue Aug 05, 2008 8:22 pm Post subject:

Since no better suggestions turned up, I'll go and call these still unnamed patterns

UR "With Strong Link" or UR wsl (pronounced weasel).

There are two types of UR weasels:

a) the "straight weasel": a pair of bi-value cells (a,b) on the SAME line (the "floor" cells). The strong link (let's say, in "a") is in a line perpendicular to the floor (NB if the strong link is parallel to the floor it is a type 4).

In this weasel, "b" (not a!) can be removed from the multi-value cell that is not part of the strong link.

nataraj · Posted: Tue Aug 05, 2008 8:25 pm Post subject:

And the well known type 6 (x-wing on a, which just means TWO parallel strong links, therefore remove a from BOTH multi-value cells) would be a double cross weasel then... Laughing