ask for help

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ask for help

Postby maria129129 » Fri Apr 14, 2017 10:58 am

I cannot work out this Sudoku. Can any body help me with it (with analysing process)? Thanks!


• • 2 | • 5 • | 7 • •
• • • | 8 3 9 | • • •
6 • • | 2 • 1 | • • 3
----------------------------------
• • 1 | • • • | 6 • •
8 6 • | • • • | • 5 7
• • 5 | • • • | 3 • •
----------------------------------
5 • • | 1 • 6 | • • 4
• • • | 7 4 8 | • • •
• • 6 | • 2 • | 9 • •
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Re: ask for help

Postby JasonLion » Fri Apr 14, 2017 12:21 pm

Right off there are three cells that can only contain a single possible digit.

When I solved this puzzle I used singles, locked candidates, a Unique Rectangle, a Hidden Pair, and a Naked Pair. There are other paths to solving the puzzle, but all of them require at least one mid-level technique (not necessarily the Unique Rectangle I used, but something more complex than Pairs).
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Re: ask for help

Postby pjb » Fri Apr 14, 2017 12:55 pm

One can even get by without any advanced method. After each naked single, be sure to remove all the numbers that can "see" the new solved number.
Naked single: r1c6 must be 4
Naked single: r3c5 must be 7
Naked single: r7c5 must be 9
Naked single: r1c4 must be 6
Naked single: r4c5 must be 8
Naked single: r5c5 must be 1
Naked single: r6c5 must be 6

3s at r9c46 only ones in box => -3 r9c128.

5s at r8c79 only ones in row => -5 r9c9.

Naked triplets of 249 at r4c89, r5c7 => -2 r6c89, -4 r6c8, -9 r6c89

9s at r4c89 only ones in box => -9 r4c124.

Naked pairs of 18 at r69c9 => -1 r128c9, -8 r1c9

Naked single: r4c9 must be 2
Naked single: r5c7 must be 4
Naked single: r4c8 must be 9
Hidden single: r5c6 must be 2
Naked single: r6c6 must be 7

4s at r23c3 only ones in column => -4 r2c12, r3c2.

Naked pairs of 18 at r16c8 => -1 r289c8, -8 r379c8

Then singles to the end

Phil
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Re: ask for help

Postby rjamil » Fri Apr 14, 2017 2:11 pm

Code: Select all
..2.5.7.....839...6..2.1..3..1...6..86.....57..5...3..5..1.6..4...748.....6.2.9..

Seven Naked Singles:
- 4 @ r1c6
- 6 @ r1c4
- 7 @ r3c5
- 9 @ r7c5
- 8 @ r4c5
- 1 @ r5c5
- 6 @ r6c5

One Hidden pair:
- 18 @ r6c89

One Naked pair:
- 35 @ r9c46

One Hidden pair
- 56 @ r28c9

One Hidden single:
- 2 @ r4c9

Two Naked singles:
- 4 @ r5c7
- 9 @ r4c8

Two Hidden singles:
- 9 @ r1c9
- 2 @ r5c6

One Naked single:
- 7 @ r6c6

One Hidden pair:
- 29 @ r68c1

One Naked pair:
- 39 @ r28c3

Rest Naked and Hidden singles to the end.

R. Jamil
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