## Hard Puzzle Solution

Advanced methods and approaches for solving Sudoku puzzles

### Hard Puzzle Solution

*3* **5 *62

**2 *6* *8*

*9* 2** **7

**9 176 5*8

*5* 9*8 *1*

**1 54* 6*9

9** 6** *4*

*6* *** 2**

7** 3** *96

Thanks
Also can anyone tell me some general methods to solving Hard Sudokus?
Thanks
Guest

I am just new here having read about this in the CM - Brisbane, Aust. I have downloaded the Sudoku trial and tried to dub your problem and it say's that this is not a valid puzzle which might explain why you are having problems.
Guest

Posts: 312
Joined: 25 November 2005

First, look where the number 2 can go in box 7.

Now take a look at that column... you can exlucde the number from the other boxes, and this allows you to fill in another number..
Animator

Posts: 469
Joined: 08 April 2005

Thanks for that clue Animator. I'm still stuck though, any more pointers?
Guest

No logical pointers...

In order to solve it you need to guess...

Did you copy it correctly? (and where did you get it?)
Animator

Posts: 469
Joined: 08 April 2005

Look at my post titled "The technique I use to solve the puzzles". Use it and there will be no guessing. Works every time for me (so far, anyway )
ccx3

Posts: 5
Joined: 22 May 2005

### Re: Hard Puzzle Solution

*3* **5 *62

**2 *6* *8*

*9* 2** **7

**9 176 5*8

*5* 9*8 *1*

**1 54* 6*9

9** 6** *4*

*6* *** 2**

7** 3** *96

Thanks
Also can anyone tell me some general methods to solving Hard Sudokus?
Thanks[/quote]
Guest

Posts: 312
Joined: 25 November 2005

ccx3 wrote:Look at my post titled "The technique I use to solve the puzzles". Use it and there will be no guessing. Works every time for me (so far, anyway :D )

I seriously doubt that... the fact that the Sudoku program says it is an invalid puzzle is already a clue... and the fact that the solvers I tried cannot solve it without guessing... so either you are using a more complex ruleset then most of us, which is very unlikely.
Animator

Posts: 469
Joined: 08 April 2005

>> Animator said: I seriously doubt that...

I don't. My response was to the question at the end:

>>Also can anyone tell me some general methods to solving Hard Sudokus?

and I stand by my reply.
ccx3

Posts: 5
Joined: 22 May 2005

Ah, sorry for the confusion then
Animator

Posts: 469
Joined: 08 April 2005

No problem, I should have made clear which bit I was replying to. "My bad" as we cool cats like to say.
Guest

Posts: 312
Joined: 25 November 2005

I keep forgetting to sign in before posting. The previous post was from ccx3.
ccx3

Posts: 5
Joined: 22 May 2005

### Solution

Here's the solution:

437 895 162
512 764 983
698 213 457
349 176 528
256 938 714
871 542 639
985 627 341
163 489 275
724 351 896

I'll explain later.
Guest

I've been waiting so long for Lma03 to explain how (s)he reached his/her solution that I thought I would try and figure it out for myself.

I started by removing eight clues (r1c8, r2c5, r3c4, r4c4, r4c9, r6c9, r7c4, and r9c9) until I found a symmetrical grid. At this point I tried solving the grid and was able to refill four of cells I had removed (plus a fifth cell which corresponded to Animator's hint) before getting stuck. I quickly discovered that the 6 at r2c5 was necessary to find the remaining three clues I had removed. Using Lma03's solution, I put an 8 at r8c5 and suddenly I had a symmetrical grid with a unique solution.

I'm guessing that Del must have accidentally lost the clue at r8c5. I think this is how the original grid should have appeared.

Code: Select all
` . 3 . | . . 5 | . . 2 . . 2 | . 6 . | . 8 . . 9 . | . . . | . . 7-------+-------+------- . . 9 | . 7 6 | 5 . . . 5 . | 9 . 8 | . 1 . . . 1 | 5 4 . | 6 . .-------+-------+------- 9 . . | . . . | . 4 . . 6 . | . 8 . | 2 . . 7 . . | 3 . . | . 9 .`
scrose

Posts: 322
Joined: 31 May 2005

### step 1 to solve

Key blocks are (column 5, row 5) and (column 6 row 6). both of these blocks can use the number 2 or 3. If you put 2 in col 5, row 5 and 3 in col 6,row 6 you don't open any new oppertunities. however if you put a 3, in col 5, row 5 and a 2 in col 6, row 6 you should be able to solve the puzzle. Next step column 9, row 5 can only be a 4. You should be able to solve from here on.
dick

Posts: 3
Joined: 21 July 2005

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