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by **urhegyi** » Fri May 07, 2021 5:52 pm

My first attempt of coding a generator for expert sudoku's. No more hidden or naked singles available from start.
I think it is to hard for an extreme puzzle, but like to hear other maybe different opinions.

Code: Select all: 6....4.5..2.1.....3...7.8.9..7..3....1..5..6.4..2..7....8.....3.9..6..4.5......9. ED=7.2/7.2/2.6

Website · by **denis_berthier** » Sat May 08, 2021 3:33 am

.
Not sure there's a well-defined notion of what "expert" level means.
This puzzle can be solved using only small Subsets and bivalue-chains of length ≤ 4 ; I wouldn't classify it as very hard ; but newspapers have lower standards.

Code: Select all: Resolution state after (indeed no) Singles: +-------------------+-------------------+-------------------+ ! 6 78 19 ! 389 2389 4 ! 123 5 127 ! ! 789 2 459 ! 1 389 5689 ! 346 37 467 ! ! 3 45 145 ! 56 7 256 ! 8 12 9 ! +-------------------+-------------------+-------------------+ ! 289 568 7 ! 4689 1489 3 ! 12459 128 12458 ! ! 289 1 239 ! 4789 5 789 ! 2349 6 248 ! ! 4 3568 3569 ! 2 189 1689 ! 7 138 158 ! +-------------------+-------------------+-------------------+ ! 127 467 8 ! 4579 1249 12579 ! 1256 127 3 ! ! 127 9 123 ! 3578 6 12578 ! 125 4 12578 ! ! 5 3467 12346 ! 3478 12348 1278 ! 126 9 12678 ! +-------------------+-------------------+-------------------+

whip[1]: c1n1{r8 .} ==> r9c3 ≠ 1, r8c3 ≠ 1
whip[1]: c8n8{r6 .} ==> r6c9 ≠ 8, r4c9 ≠ 8, r5c9 ≠ 8
whip[1]: r3n6{c6 .} ==> r2c6 ≠ 6
whip[1]: r3n4{c3 .} ==> r2c3 ≠ 4

Code: Select all: Resolution state after Singles and whips[1]: +-------------------+-------------------+-------------------+ ! 6 78 19 ! 389 2389 4 ! 123 5 127 ! ! 789 2 59 ! 1 389 589 ! 346 37 467 ! ! 3 45 145 ! 56 7 256 ! 8 12 9 ! +-------------------+-------------------+-------------------+ ! 289 568 7 ! 4689 1489 3 ! 12459 128 1245 ! ! 289 1 239 ! 4789 5 789 ! 2349 6 24 ! ! 4 3568 3569 ! 2 189 1689 ! 7 138 15 ! +-------------------+-------------------+-------------------+ ! 127 467 8 ! 4579 1249 12579 ! 1256 127 3 ! ! 127 9 23 ! 3578 6 12578 ! 125 4 12578 ! ! 5 3467 2346 ! 3478 12348 1278 ! 126 9 12678 ! +-------------------+-------------------+-------------------+

hidden-pairs-in-a-row: r2{n4 n6}{c7 c9} ==> r2c9 ≠ 7, r2c7 ≠ 3
hidden-pairs-in-a-block: b1{n7 n8}{r1c2 r2c1} ==> r2c1 ≠ 9
whip[1]: c1n9{r5 .} ==> r5c3 ≠ 9, r6c3 ≠ 9
whip[1]: r6n9{c6 .} ==> r4c4 ≠ 9, r4c5 ≠ 9, r5c4 ≠ 9, r5c6 ≠ 9
naked-pairs-in-a-column: c3{r5 r8}{n2 n3} ==> r9c3 ≠ 3, r9c3 ≠ 2, r6c3 ≠ 3
biv-chain[2]: r1n7{c2 c9} - c8n7{r2 r7} ==> r7c2 ≠ 7
naked-pairs-in-a-block: b7{r7c2 r9c3}{n4 n6} ==> r9c2 ≠ 6, r9c2 ≠ 4
biv-chain[3]: r3c4{n5 n6} - b5n6{r4c4 r6c6} - r6c3{n6 n5} ==> r3c3 ≠ 5
biv-chain[3]: b1n5{r3c2 r2c3} - r6c3{n5 n6} - c6n6{r6 r3} ==> r3c6 ≠ 5
biv-chain[3]: b2n2{r1c5 r3c6} - c6n6{r3 r6} - r6n9{c6 c5} ==> r1c5 ≠ 9
biv-chain[4]: r1c2{n8 n7} - b3n7{r1c9 r2c8} - c8n3{r2 r6} - b6n8{r6c8 r4c8} ==> r4c2 ≠ 8
naked-pairs-in-a-block: b4{r4c2 r6c3}{n5 n6} ==> r6c2 ≠ 6, r6c2 ≠ 5
biv-chain[3]: r6c2{n8 n3} - r5n3{c3 c7} - r5n9{c7 c1} ==> r5c1 ≠ 8
whip[1]: r5n8{c6 .} ==> r4c4 ≠ 8, r4c5 ≠ 8, r6c5 ≠ 8, r6c6 ≠ 8
hidden-pairs-in-a-block: b5{n7 n8}{r5c4 r5c6} ==> r5c4 ≠ 4
whip[1]: r5n4{c9 .} ==> r4c7 ≠ 4, r4c9 ≠ 4
hidden-pairs-in-a-row: r6{n3 n8}{c2 c8} ==> r6c8 ≠ 1
biv-chain[3]: r4c4{n4 n6} - r6n6{c6 c3} - r9c3{n6 n4} ==> r9c4 ≠ 4
biv-chain[3]: c4n4{r7 r4} - r4n6{c4 c2} - r7c2{n6 n4} ==> r7c5 ≠ 4
biv-chain[4]: b2n2{r1c5 r3c6} - b2n6{r3c6 r3c4} - r4c4{n6 n4} - b8n4{r7c4 r9c5} ==> r9c5 ≠ 2
biv-chain[2]: c5n2{r7 r1} - r3n2{c6 c8} ==> r7c8 ≠ 2
biv-chain[3]: r3c8{n2 n1} - r7c8{n1 n7} - b3n7{r2c8 r1c9} ==> r1c9 ≠ 2
biv-chain[3]: c1n1{r8 r7} - r7c8{n1 n7} - r2n7{c8 c1} ==> r8c1 ≠ 7
x-wing-in-columns: n7{c1 c8}{r2 r7} ==> r7c6 ≠ 7, r7c4 ≠ 7
biv-chain[4]: c2n8{r1 r6} - r4n8{c1 c8} - c8n2{r4 r3} - b2n2{r3c6 r1c5} ==> r1c5 ≠ 8
biv-chain[3]: c5n8{r2 r9} - b8n4{r9c5 r7c4} - c4n9{r7 r1} ==> r1c4 ≠ 8, r2c5 ≠ 9
stte

by **Cenoman** » Sat May 08, 2021 2:38 pm

Four rather simple steps:

Code: Select all: +---------------------+-------------------------+------------------------+ | 6 78* 19 | 389 2389 4 | b123 5 127* | | a78 2 59 | 1 389 589 | 46 a37* 46 | | 3 45 145 | 56 7 256 | 8 12 9 | +---------------------+-------------------------+------------------------+ | 289 568 7 | 468 148 3 | 12459 128 1245 | | d29-8 1 23 | 478 5 78 | c2349 6 24 | | 4 3568 56 | 2 189 1689 | 7 138 15 | +---------------------+-------------------------+------------------------+ | 127 46-7 8 | 4579 1249 12579 | 1256 127* 3 | | 127 9 23 | 3578 6 12578 | 125 4 12578 | | 5 3467 46 | 3478 12348 1278 | 126 9 12678 | +---------------------+-------------------------+------------------------+

1. Kite (7)r1c2 = r1c9 - r2c8 = r7c8 => -7 r7c2
2. ALS M-Wing (8=73)r2c18 - r1c7 = (3-9)r5c7 = (9)r5c1 => -8 r5c1

Code: Select all: +-------------------+-------------------------+-----------------------+ | 6 78 B19 | C389 2389 4 | 123 5 127 | | 78 2 59 | 1 389 589 | 46 37 46 | | 3 B45 B145 | A56 7 256 | 8 12 9 | +-------------------+-------------------------+-----------------------+ | 289 a56 7 |Aa46 14 3 | 1259 128 125 | | 29 1 23 | 78 5 78 | 2349 6 24 | | 4 38 b56 | 2 19 169 | 7 38 15 | +-------------------+-------------------------+-----------------------+ | 127 46 8 | D579-4 1249 12579 | 1256 127 3 | | 127 9 23 | 3578 6 12578 | 125 4 12578 | | 5 37 b46 | 378-4 12348 1278 | 126 9 12678 | +-------------------+-------------------------+-----------------------+

3. ALS-XZ(4=65)r4c24 - (5=64)r69c3 => -4 r9c4
4. ALS H-Wing (4=65)r34c4 - (5=149)b1p389 - r1c4 = (9)r7c4 => -4r7c4; ste

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