dailysudoku.com

keith · Posted: Sat May 27, 2006 9:13 am Post subject: DB Saturday Puzzle - May 27, 2006

Here it is:

Marty R. · Posted: Sat May 27, 2006 4:58 pm Post subject:

My take: the puzzle started off generously, allowing five cells to be solved during the initial scan of bands and stacks. After filling in cells with their candidates and doing the usual scan of rows, columns and blocks, a nice Type 1 rectangle of 78 was exposed. This eliminated some candidates, solved some cells and exposed a 17 Type 1 rectangle.

Whoops! That 78 rectangle was in FOUR boxes! A very easy trap to fall into if one's brain is not focused on ALL details at ALL times. I tried to re-create the grid as it was before that false rectangle, thinking that the puzzle would end up with duplicates as a result of my error. But, I found out, I was fortunate enough to have re-created the grid correctly.

Further scanning exposed two more Type 1 rectangles of 37 and 36 and that was enough to finish it off.

Type 1 rectangles are right up my alley, as they are very compatible with my reasoning powers. Laughing

keith · Posted: Sat May 27, 2006 10:37 pm Post subject: A lesson?

Marty,

Your message just reinforces my opinion that Unique Rectangles are easy for humans. Use them when you find them.

If you use the "official" hierarchy of solution methods with this puzzle, you get to here:

David Bryant · Joined: 29 Jul 2005 Posts: 559 Location: Denver, Colorado

ravel · Joined: 21 Apr 2006 Posts: 536

keith · Posted: Mon May 29, 2006 12:19 pm Post subject:

Ravel,

If R7C7 is <4>, it forces both R6C7 and R7C8 to be <7>. Then, the strong link in R6 forces R6C8 to be <4>, and you have the deadly solution.

Keith

ravel · Joined: 21 Apr 2006 Posts: 536

Thanks Keith,

i had looked at the wrong cell, i mixed R7C7 and R7C8 Smile