The New Sudoku Players' Forum

by **lerfalds** » Sat Mar 11, 2006 2:40 am

I have worked on this puzzle for hours. I just tried to learn coloring, but it didn't seem to work. I tried coloring the 3's starting with r3c5 green, then r3c6 and r5c5 blue, etc. Maybe I didn't fully understand it. Please help - this puzzle is driving me crazy. Thanks!!

6 3 1 7 9 5 4 8 2
9 8 5 1 4 2 6 3 7
4 2 7 86 36 38 5 9 1
138 16 2 4 7 38 9 5 36
5 9 36 2 36 1 8 7 4
38 7 4 68 5 9 2 1 36
2 16 68 9 18 7 3 4 5
13 4 38 5 18 6 7 2 9
7 5 9 3 2 4 1 6 8
[/code]

by **Chessmaster** » Sat Mar 11, 2006 3:51 am

is this from sudoku for dummies 1 or 2

by **emm** » Sat Mar 11, 2006 4:07 am

Here are the 3s – there are two separate chains Aa and Bb – they are not connected and no 3s can be eliminated.

Code: Select all: . . . | . . . | . . . . . . | . . . | . . . . . . | . 3A 3a| . . . ----------+---------+-------- 3 . . | . . 3A| . . 3B . . 3A | . 3a . | . . . 3B . . | . . . | . . 3b ----------+---------+-------- . . . | . . . | . . . 3A . 3a | . . . | . . . . . . | . . . | . . .

This puzzle has a classic BUG pattern – every number appears exactly twice in every row, column and box – except for one cell = r4c1. If each number was exactly twice in the grid then you would have two possible solutions. Assuming that this is a Sudoku with a unique solution, you have to place the only number that prevents the BUG pattern => r4c1 = 3

Code: Select all: *--------------------------------------------------* | 6 3 1 | 7 9 5 | 4 8 2 | | 9 8 5 | 1 4 2 | 6 3 7 | | 4 2 7 | 68 36 38 | 5 9 1 | |----------------+----------------+----------------| | 138* 16 2 | 4 7 38 | 9 5 36 | | 5 9 36 | 2 36 1 | 8 7 4 | | 38 7 4 | 68 5 9 | 2 1 36 | |----------------+----------------+----------------| | 2 16 68 | 9 18 7 | 3 4 5 | | 13 4 38 | 5 18 6 | 7 2 9 | | 7 5 9 | 3 2 4 | 1 6 8 | *--------------------------------------------------*

Alternatively, there is an XY wing at r4c6, r4c9 and r6c4 that eliminates the 6 from r6c9.
If you have two cells in a group that share a candidate - r4c6 (XY) and r4c9 (XZ) – and a third cell with the unshared candidates – r6c4 (ZY) – also shares a group with one of those cells, then no cell that ‘sees’ both Zs can be Z and no cell that 'sees' both Ys can be Y. In this case r6c9 <> 6.

This can be explained as a forcing chain
r4c6=3 => r4c9=6 => r6c9<>6
r4c6=8 => r6c4=6 => r6c9<>6

by **QBasicMac** » Sat Mar 11, 2006 4:31 am

If r5c3=3 then r6c1=8. That leaves 6 in r5c5 and r6c4 - impossible.
Therefore r5c3=6

by **tarek** » Sat Mar 11, 2006 9:53 am

This solves it.

Code: Select all: *-----------------------------------------------* | 6 3 1 | 7 9 5 | 4 8 2 | | 9 8 5 | 1 4 2 | 6 3 7 | | 4 2 7 | 68 36 38 | 5 9 1 | |---------------+---------------+---------------| | 138 16 2 | 4 7 38 | 9 5 36 | | 5 9 36 | 2 36 1 | 8 7 4 | | 38 7 4 | 68 5 9 | 2 1 36 | |---------------+---------------+---------------| | 2 16 68 | 9 18 7 | 3 4 5 | | 13 4 38 | 5 18 6 | 7 2 9 | | 7 5 9 | 3 2 4 | 1 6 8 | *-----------------------------------------------* Eliminating 6 From r6c9 (3 & 8 in r4c6 form an XY wing with 6 in r4c9 & r6c4)

Tarek

by **lerfalds** » Sat Mar 11, 2006 8:14 pm

Thanks everyone for the help!!

Chessmaster - This puzzle is from Dummies 1.

EM - I think I finally understand xy wing. Thanks!!

Lerfalds

by **tommy** » Mon Mar 13, 2006 10:10 pm

hello anyone and everyone.

I am a newbie at this sudoku game and i love it.

I can do the easy puzzles, the tricky ones , and most tough ones.

I even have completed a few of the diabolical ones.

I have been using the sudoku for dummies and i clearly see i need to advance my skills. I would very much appreciate any help. I found this sight and by reading this forum I can see i have a lot to learn.

I want to be able to solve the more difficult puzzles using logic and not resorting to a guess.

tommy

The New Sudoku Players' Forum

please help with puzzle 187 - tough from sudoku for dummies

please help with puzzle 187 - tough from sudoku for dummies

THANKS!!