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I propose this newly created, small, but challenging Hidoku puzzle (for a manual solution !)
.---------------------.
7 | . . . . 5 . 24|
6 | . 31 . . . . . |
5 | . . . . . . . |
4 | . 34 . 49 . . . |
3 | . 35 37 1 . 45 . |
2 | . . . . . . . |
1 | . . . 39 18 . . |
'---------------------'JCO#11
a b c d e f g
I propose the following Classic Sudoku puzzle solvable in two steps.
(found with Sudoku Architect)
After basics
,----------------------------------------------------------,
9 | 1269 129 129 | 268 5 2389 | 4 1378 3789 |
8 | 7 259 8 | 4 1 239 | 69 35 3569 |
7 | 1569 3 4 | 68 7 89 | 2 158 589 |
|-------------------+---------------+----------------------|
6 | 2589 7 259 | 1 3 256 | 69 4 2689 |
5 | 1238 128 12 | 9 4 267 | 5 2378 23678 |
4 | 23459 2459 6 | 257 8 257 | 1 237 2379 |
|-------------------+---------------+----------------------|
3 | 18 6 17 | 78 9 4 | 3 25 25 |
2 | 24 24 3 | 578 6 578 | 78 9 1 |
1 | 589 589 579 | 3 2 1 | 78 6 4 |
'----------------------------------------------------------'
a b c d e f g h i
Update 1 (Jun 23, 2026)
The weakness of this puzzle is the bivalued cells at the third row:
(18)a3, (17)c3, (78)d3 and their relations to cells in other boxes,
as indicated below (partially).
,----------------------------------------------------------,
9 | 1269 129 129 |{268} 5 2389 | 4 1378 3789 |
8 | 7 259 8 | 4 1 239 | 69 35 3569 |
7 | 1569 3 4 |{68} 7 89 | 2 158 589 |
|-------------------+---------------+----------------------|
6 | 2589 7 259 | 1 3 256 | 69 4 2689 |
5 | 1238 128 [12] | 9 4 267 | 5 2378 23678 |
4 | 23459 2459 6 | 257 8 257 | 1 237 2379 |
|-------------------+---------------+----------------------|
3 |(18) 6 (17) |(78) 9 4 | 3 25 25 |
2 | 24 24 3 | 578 6 578 | 78 9 1 |
1 | 589 589 579 | 3 2 1 | 78 6 4 |
'----------------------------------------------------------'
a b c d e f g h i
Can you find a key target and the move that eliminates that
target [producing 15 placements and nearly solving the puzzle] ?
Update 2 (Jun 25, 2026)
,----------------------------------------------------------,
9 | 1269 129 129 | 26-8 5 2389 | 4 1378 3789 |
8 | 7 259 8 | 4 1 239 | 69 35 3569 |
7 | 1569 3 4 | 6-8 7 89 | 2 158 589 |
|-------------------+---------------+----------------------|
6 | 2589 7 259 | 1 3 256 | 69 4 [2]689 |
5 | 1238 128 [12] | 9 4 267 | 5 2378 23678 |
4 | 23459 2459 6 | 257 8 257 | 1 237 2379 |
|-------------------+---------------+----------------------|
3 |(18) 6 (17) |(78) 9 4 | 3 25 25 |
2 | 24 24 3 | 578 6 57-8 | 78 9 1 |
1 | 589 589 579 | 3 2 1 | 78 6 4 |
'----------------------------------------------------------'
a b c d e f g h i
Notice the almost chain
(8=71)c3.d3 - (1=2)c5 - (2)a6.c6 *= (2)f6 - (2=578)d2.d3.d4 => -8 d79, -8 f2
The move is valid if one can show that (2)i6 being true also removes
the same canditates [it does !]. How to show this ?
Update 3 (Jun 26, 2026)
After the previous almost-chain which is releated to
Kraken Row (2)ac6,f6,i6 => -2 d4 [15 placements and basics] we get
,-----------------------------------------------------,
9 | 6 19 19 | 2 5 38 | 4 378 378 |
8 | 7 2 8 | 4 1 39 | 69 35 3569 |
7 | 5 3 4 | 6 7 89 | 2 1 89 |
|-------------------+-------------+-------------------|
6 | 89 7 259 | 1 3 256 | 69 4 2689 |
5 | 3 18 12 | 9 4 267 | 5 278 2678 |
4 | 4 59 6 | 57 8 257 | 1 237 2379 |
|-------------------+-------------+-------------------|
3 | 1 6 7 | 8 9 4 | 3 25 25 |
2 | 2 4 3 | 57 6 57 | 8 9 1 |
1 | 89 589 59 | 3 2 1 | 7 6 4 |
'-----------------------------------------------------'
a b c d e f g h i
Now finding, for instance, a Y-wing solves the puzzle.
Consider the following chess position:
White: Kg2, f2, g3, g4, d4; Black: Kg8, g7, f7, g5, d5.
Now it is White's turn and White plays 1. Kf1.
What should be black's response ? How the game should continue with correct play ?
Created: February 12, 2024
Contact: sudo.jco.br@gmail.com