The New Sudoku Players' Forum

by **P.O.** » Wed Jul 19, 2023 5:57 pm

Code: Select all: . . 5 . 4 1 8 . . . 7 . . . 2 . 3 . . . . . . . . . 1 6 . . . 1 . . . 9 . 5 . . . 4 . 7 . . . 4 . . . 2 . . . 2 . . . 3 . 6 . . . 8 . 5 . . . 3 . 1 . . . . . . . ..5.418...7...2.3.........16...1...9.5...4.7...4...2...2...3.6...8.5...3.1....... 239 369 5 3679 4 1 8 29 267 1489 7 169 5689 689 2 4569 3 456 23489 34689 2369 356789 36789 56789 45679 2459 1 6 38 237 23578 1 578 345 458 9 12389 5 1239 23689 23689 4 136 7 68 13789 389 4 356789 36789 56789 2 158 568 4579 2 79 14789 789 3 14579 6 4578 479 469 8 124679 5 679 1479 1249 3 34579 1 3679 246789 26789 6789 4579 24589 24578

by **shye** » Wed Jul 19, 2023 7:25 pm

Code: Select all: ,--------------------,----------------------,---------------------, |#239 #369 5 | 367-9 4 1 | 8 #29 67-2 | | 1489 7 169 | 5689 689 2 | 4569 3 456 | | 23489 34689 2369 | 356789 36789 56789 | 45679 2459 1 | :--------------------+----------------------+---------------------: | 6 38 237 | 23578 1 578 | 345 458 9 | | 12389 5 1239 | 23689 23689 4 | 136 7 68 | | 13789 389 4 | 356789 36789 56789 | 2 158 568 | :--------------------+----------------------+---------------------: | 4579 2 79 | 14789 789 3 | 14579 6 4578 | | 479 *469 8 | 124679 5 679 | 1479 1249 3 | |*34579 1 *3679 | 246789 26789 6789 | 4579 24589 24578 | '--------------------'----------------------'---------------------'

(29=3)r1c18 - 36b7p79 = 6b7p5 - (6=239)r1c128
=> -29r1c49

Code: Select all: ,---------------,--------------,----------------, | 239 #39 5 | 6 4 1 | 8 2-9 7 | | 189 7 169 | 589 89 2 | 4569 3 456 | | 289 4 69 | 3 7 589 | 569 259 1 | :---------------+--------------+----------------: | 6 *38 2 | 7 1 58 |*345 *458 9 | | 1389 5 139 | 89 2 4 | 36 7 68 | | 7 89 4 | 589 3 6 | 2 1 58 | :---------------+--------------+----------------: | 459 2 79 | 1 89 3 | 4579 6 458 | | 49 6 8 | 2 5 7 | 1 #49 3 | | 359 1 379 | 4 6 89 | 579 589 2 | '---------------'--------------'----------------'

(9=3)r1c2 - 34r4c27 = 4r4c8 - (4=9)r8c8
=> -9r1c8 stte

by **P.O.** » Fri Jul 21, 2023 5:57 pm

thank you for your answer, my solution uses a nested chain to get to the antibackdoor:
n3r13c2 OR n3r46c2 => r1c8 <> 9
ste.

Code: Select all: ((3 0 2 0) ((1 2 1) (3 6 9)) ((3 2 1) (3 4 6 8 9))) n3r13c2 29 36 5 3679 4 1 8 29 267 1489 7 169 5689 689 2 4569 3 456 2489 346 269 356789 36789 56789 45679 2459 1 6 8 237 2357 1 57 345 45 9 123 5 123 23689 23689 4 136 7 68 137 9 4 35678 3678 5678 2 158 568 4579 2 79 14789 789 3 14579 6 4578 479 46 8 124679 5 679 1479 1249 3 34579 1 3679 246789 26789 6789 4579 24589 24578 9r1c8 => r4c78 <> 4 let A be r1c8=9 - r1c1{n9 n2} - c9n2{r1 r9} - c5n2{r9 r5} - 13r5c13 A - c7n3{r5 r4} A - r6n1{c1 c8} - r8c8{n129 n4} => r1c8 <> 9

Code: Select all: ((3 0 2 0) ((4 2 4) (3 8)) ((6 2 4) (3 8 9))) n3r46c2 239 69 5 3679 4 1 8 29 267 1489 7 169 5689 689 2 4569 3 456 23489 4689 2369 356789 36789 56789 45679 2459 1 6 38 27 23578 1 578 345 458 9 1289 5 129 23689 23689 4 136 7 68 1789 389 4 356789 36789 56789 2 158 568 4579 2 79 14789 789 3 14579 6 4578 479 469 8 124679 5 679 1479 1249 3 34579 1 3679 246789 26789 6789 4579 24589 24578 9r1c8 => r8c8 <> 1,2,4,9 let A be r1c8=9 - - r1c2{n9 n6} - b7n6{r8c2 r9c3} - c3n3{r9 r3} - r1c1{n39 n2} - c9n2{r1 r9} - r8n2{c8 c4} - r4n2{c4 c3} - b4n7{r4c3 r6c1} | r8c8<>2 A - r6n1{c1 c8} A - 49r8c12 => r1c8 <> 9

Puzzle 142