The New Sudoku Players' Forum

[Leren]

As you have Hodoku you can check their solution. They use a couple of single digit patterns, which are described here and AIC's, which are described here. Instead of AIC's you can try Almost Locked Set chains, which are described here.

Leren

[AnotherLife]

I asked you a question about this sudoku because I didn't like the solutions based on AICs that are given by both HoDoKu and Andrew Stuart's Solver. After a few relatively simple steps we come to a situation where we can use one Almost Locked Set A=r456c2{1489} to eliminate two candidates. The first method is called Death Blossom in HoDoKu and Aligned Pair Exclusion in Andrew's Solver, the second is the Almost Locked Set XZ-Rule. So r9c2<>1, r5c1<>4, and we can also eliminate the two 1's from r56c1 using Box/Line Reduction. After that, we have a long sequence of singles. I think this solution is more human and more logical than that suggested by the programmes. Do you agree? https://yadi.sk/i/LZob-EQOiZs73A https://yadi.sk/i/W1uBRTeWAtoi4Q

[AnotherLife]

I think that my solution given above becomes more understandable if we make use of two Almost Locked Sets A=r456c2 {1489} (painted brown) and C=r7c2 {58} (painted green) in one method called ALS XY-Wing.
1. If we consider B=r9c3 {15} (painted yellow) as the third ALS, we can eliminate the 1 from r9c2.
2. If we consider B=r89c1,r9c23 {13457} (painted yellow) as the third ALS, we can eliminate the 4 from r5c1.
See the links to the corresponding images: https://yadi.sk/i/1YMfrGtXKdypiA https://yadi.sk/i/xhbIZXw9fXp3Pg