Help with hint (re: X-Wing)

[mkizer]

I am currently playing a puzzle (Fiendish 9500) and got to a point where I was stuck, so I tried hints. It said that there was an X-Wing in columns for 5. I'm not super clear on how to "see" X-Wings yet, so if someone could explain it a bit more for me, that'd be great! :)

Original puzzle, to the point where I got stuck:
http://ivorygate.com/temp/palm1.png

X-Wings in columns for 5:
http://ivorygate.com/temp/palm2.png

Highlighted all 5s in the puzzle:
http://ivorygate.com/temp/palm3.png

[Howard]

Hiya, did you see the pages at http://www.palmsudoku.com/ about X-Wings? Plenty more diagrams there to help :)

In your example, the highlighted 5s in those two columns tell you that the 5s in the top two rows MUST be in those two columns, so all of the other possibilities for 5's (the others in rows 1 and 2) can be removed.

That should help you to make progress :)

Howard.

[mkizer]

Hiya, did you see the pages at http://www.palmsudoku.com/ about X-Wings? Plenty more diagrams there to help :)
Yip, I've read through those techniques a few times. I just started playing Sudoku when the Palm version was released, so I'm still learning some of the more advanced techniques and that site has definitely helped.

I understand what the X-Wings technique does logically, and it makes sense. I think I am just having a hard time "seeing" the X-Wing in the first place.

In this example, if you looked in each column for a number that occurs exactly twice in the pencil markings, and find another column where that same number appears exactly twice and in the same rows as the other column, you have an X-Wing scenario. Or like the examples show, the numbers form the corners of a rectangle.

So for this example, those four corners of the rectangle are the only possible places where the 5 can be placed (for the top 3 boxes in the puzzle). All other candidates for 5 can be removed from rows 1 & 2 (and row 3 from box 3).

I think I'm getting the hang of it. ;)

[mmurph211]

Hi,

there's some good links in a post here for X-Wing and Swordfish strategies:
Advanced Sudoku Strategies (http://www.razzlechallenge.com/razzle/razzle/post/18)

jboy

[jetberrocal]

I am new with Sudoku. I also do not understand the X-Win or Swordfish.

I got stop with the following puzzle:
(Blue is for found numbers, black is for original numbers)

[8,9345,62][7,2356,356][1,46,54]
[3459,359,67][569,356,1][2,8,547]
[15,15,627][256,4,8][3,67,9]
[15,2,9][45,1735,7345][6,134,8]
[14,6,3][28,28,9][7,5,14]
[7,145,8][456,1356,3456][9,2,134]
[6,837,5][1,9,47][84,37,2]
[2,879,4][3,6857,657,85,179,17]
[39,8379,1][458,857,2][854,937,6]

I can found a lot of cycles but which one(s) is/are the true X-Win(s) :confused: