Analysis of zz-www.sudokuoftheday.co.uk-20190304-absurd-base.sdk

Contents

Sudoku from http://www.sudokuoftheday.co.uk/cgi-bin/sudoku1280.cgi?ACTION=archive2&USER=&MONTH=Mar&YEAR=2019

level: medium

Sudoku from http://www.sudokuoftheday.co.uk/cgi-bin/sudoku1280.cgi?ACTION=archive2&USER=&MONTH=Mar&YEAR=2019

position: .6....4....2.........78..59...3.6....8142.....9....2...4...9...3.......7.2..78..1 initial

Autosolve

position: .6....4....2......1347826592..396..468142....4938..2...4.139...31.2....7.2..78341 autosolve
Autosolve

Pair Reduction Variants

Pair Reduction Analysis

Pair Reduction Analysis

The following important HDP chains were detected:

* PRF # C1: 5,7 => SOL
* DIS # A2: 5,7 => CTR => A2: 8,9
* PRF # D2: 5,9 => SOL
* DIS # D2: 6 => CTR => D2: 5,9
* PRF # A1: 5,9 => SOL
* DIS # C1: 5,9 => CTR => C1: 7,8
* PRF # C1: 7,8 => SOL
* DIS # F1: 1,5 => CTR => F1: 3
* DIS # F2: 1,5 => CTR => F2: 3,4
* PRF # C1: 5,7 => SOL
* DIS # F6: 5,7 => CTR => F6: 1
* DIS # F6: 7 => CTR => F6: 1,5
* DIS # G2: 1,8 => CTR => G2: 7
* PRF # C9: 5,9 => SOL
* DIS # C9: 6 => CTR => C9: 5,9
* PRF # A1: 5,9 => SOL
* PRF # F2: 4,5 => SOL
* DIS # F2: 1,3 => CTR => F2: 4,5
* DIS # C9: 5,6 => CTR => C9: 9
* PRF # C9: 9 => SOL
* DIS # D2: 5,6 => CTR => D2: 9
* PRF # D2: 9 => SOL
* DIS # I7: 5,8 => CTR => I7: 2,6
* CNT  23 HDP CHAINS /  49 HYP OPENED

See Appendix: Full HDP Chains for full list of HDP chains.

Pair Reduction

Pair Reduction

The following important HDP chains were detected:

* PRF # C1: 5,7 => SOL
* STA C1: 5,7
* CNT   1 HDP CHAINS /   2 HYP OPENED

See Appendix: Full HDP Chains for full list of HDP chains.

Details

Positions

.6....4....2.........78..59...3.6....8142.....9....2...4...9...3.......7.2..78..1 initial
.6....4....2......1347826592..396..468142....4938..2...4.139...31.2....7.2..78341 autosolve
967513428852964713134782659275396184681427935493851276748139562316245897529678341 solved

Classification

level: medium

Pairing Analysis

--------------------------------------------------
* PAIRS (19)
B2: 5,7
D1: 5,9
E1: 1,5
E2: 4,6
I2: 3,8
B4: 5,7
C4: 5,7
F5: 5,7
E6: 1,5
G4: 1,8
H4: 1,8
I5: 3,5
H6: 6,7
I6: 5,6
A9: 5,9
E8: 4,6
F8: 4,5
D9: 5,6
G7: 5,8

--------------------------------------------------
* CONSTRAINT PAIRS (AUTO SOLVE)
E6,F6: 1.. / E6 = 1  =>  0 pairs (X) / F6 = 1  => 21 pairs (_)
G4,H4: 1.. / G4 = 1  => 20 pairs (_) / H4 = 1  =>  0 pairs (X)
E1,E6: 1.. / E1 = 1  => 21 pairs (_) / E6 = 1  =>  0 pairs (X)
G2,G4: 1.. / G2 = 1  =>  0 pairs (X) / G4 = 1  => 20 pairs (_)
H1,I1: 2.. / H1 = 2  => 19 pairs (_) / I1 = 2  => 19 pairs (_)
H7,I7: 2.. / H7 = 2  => 19 pairs (_) / I7 = 2  => 19 pairs (_)
H1,H7: 2.. / H1 = 2  => 19 pairs (_) / H7 = 2  => 19 pairs (_)
I1,I7: 2.. / I1 = 2  => 19 pairs (_) / I7 = 2  => 19 pairs (_)
F1,F2: 3.. / F1 = 3  => 20 pairs (_) / F2 = 3  =>  0 pairs (X)
H5,I5: 3.. / H5 = 3  => 19 pairs (_) / I5 = 3  => 20 pairs (_)
E2,F2: 4.. / E2 = 4  =>  0 pairs (X) / F2 = 4  =>  0 pairs (_)
E8,F8: 4.. / E8 = 4  =>  0 pairs (*) / F8 = 4  =>  0 pairs (X)
E2,E8: 4.. / E2 = 4  =>  0 pairs (X) / E8 = 4  =>  0 pairs (_)
F2,F8: 4.. / F2 = 4  =>  0 pairs (*) / F8 = 4  =>  0 pairs (X)
B4,C4: 5.. / B4 = 5  =>  0 pairs (X) / C4 = 5  => 19 pairs (_)
F8,D9: 5.. / F8 = 5  =>  0 pairs (*) / D9 = 5  =>  0 pairs (X)
B2,B4: 5.. / B2 = 5  => 19 pairs (_) / B4 = 5  =>  0 pairs (X)
E1,E6: 5.. / E1 = 5  =>  0 pairs (X) / E6 = 5  => 21 pairs (_)
D2,E2: 6.. / D2 = 6  =>  0 pairs (X) / E2 = 6  =>  0 pairs (_)
H6,I6: 6.. / H6 = 6  =>  0 pairs (X) / I6 = 6  => 22 pairs (_)
E8,D9: 6.. / E8 = 6  =>  0 pairs (X) / D9 = 6  =>  0 pairs (_)
C9,D9: 6.. / C9 = 6  =>  0 pairs (X) / D9 = 6  =>  0 pairs (_)
D2,D9: 6.. / D2 = 6  =>  0 pairs (X) / D9 = 6  =>  0 pairs (_)
E2,E8: 6.. / E2 = 6  =>  0 pairs (*) / E8 = 6  =>  0 pairs (X)
I6,I7: 6.. / I6 = 6  => 22 pairs (_) / I7 = 6  =>  0 pairs (X)
B4,C4: 7.. / B4 = 7  => 19 pairs (_) / C4 = 7  =>  0 pairs (X)
F5,F6: 7.. / F5 = 7  => 22 pairs (_) / F6 = 7  =>  0 pairs (X)
A7,C7: 7.. / A7 = 7  => 19 pairs (_) / C7 = 7  => 26 pairs (_)
F6,H6: 7.. / F6 = 7  =>  0 pairs (X) / H6 = 7  => 22 pairs (_)
B2,B4: 7.. / B2 = 7  =>  0 pairs (X) / B4 = 7  => 19 pairs (_)
G2,G5: 7.. / G2 = 7  => 22 pairs (_) / G5 = 7  =>  0 pairs (X)
G4,H4: 8.. / G4 = 8  =>  0 pairs (X) / H4 = 8  => 20 pairs (_)
D1,D2: 9.. / D1 = 9  =>  0 pairs (X) / D2 = 9  =>  0 pairs (_)
G5,H5: 9.. / G5 = 9  => 24 pairs (_) / H5 = 9  => 22 pairs (_)
A9,C9: 9.. / A9 = 9  =>  0 pairs (X) / C9 = 9  =>  0 pairs (_)
G8,H8: 9.. / G8 = 9  => 22 pairs (_) / H8 = 9  => 24 pairs (_)
A2,D2: 9.. / A2 = 9  =>  0 pairs (X) / D2 = 9  =>  0 pairs (_)
C1,C9: 9.. / C1 = 9  =>  0 pairs (X) / C9 = 9  =>  0 pairs (_)
G5,G8: 9.. / G5 = 9  => 24 pairs (_) / G8 = 9  => 22 pairs (_)
H5,H8: 9.. / H5 = 9  => 22 pairs (_) / H8 = 9  => 24 pairs (_)
* DURATION: 0:01:00.765513  START: 04:13:03.045028  END: 04:14:03.810541 2019-05-01
* CP COUNT: (40)
* SOLUTION FOUND

--------------------------------------------------
* PREPARE PR GRAPH
* PAIR REDUCTION ..
* LEVEL 0 PASS 1 ROUND 1 (AUTO SOLVE) (A9,B2,B4,C4,D1,D9,E1,E2,E6,E8,F5,F8,G4,G7,H4,H6,I2,I5,I6)
* .6....4....2......1347826592..396..468142....4938..2...4.139...31.2....7.2..78341
* PAIR B2: 5,7 BLK 1
A1: 5,7,8,9                              # reduction candidate for 5,7
A1: 5,7                                  # 22 pairs
C1: 5,7,8,9                              # reduction candidate for 5,7
C1: 5,7 => SOLVED
* 967513428852964713134782659275396184681427935493851276748139562316245897529678341
C1: 8,9                                  # 20 pairs
A2: 5,7,8,9                              # reduction candidate for 5,7
A2: 5,7 => CTR
* .6.5134....296471.1347826592..396..4681427...493851276.4.139...31.245..7.2.678341
A2: 8,9                                  # 20 pairs
* PAIR D1: 5,9 BLK 2
D2: 5,9,6                                # reduction candidate for 5,9
D2: 5,9 => SOLVED
* 967513428852964713134782659275396184681427935493851276748139562316245897529678341
D2: 6 => CTR
* .6.9..4..9.264....1347826592..396..468142....4938..2...4.139...31.264..752..78341
* PAIR D1: 5,9 ROW 1
A1: 5,9,7,8                              # reduction candidate for 5,9
A1: 5,9 => SOLVED
* 967513428852964713134782659275396184681427935493851276748139562316245897529678341
A1: 7,8                                  # 20 pairs
C1: 5,9,7,8                              # reduction candidate for 5,9
C1: 5,9 => CTR
* 76..134..852964713134782659275396184681427.3549385127654713986231.2....7.2..78341
C1: 7,8 => SOLVED
* 967513428852964713134782659275396184681427935493851276748139562316245897529678341
* PAIR E1: 1,5 BLK 2
F1: 1,5,3                                # reduction candidate for 1,5
F1: 1,5 => CTR
* .6.9..4..9.2..3..81347826592..396..468142....4938..2...4.139...31.2.4..7.2.578341
F1: 3                                    # 20 pairs
F2: 1,5,3,4                              # reduction candidate for 1,5
F2: 1,5 => CTR
* .69..34....2.4....1347826592..396..468142....4938..2...4.139...31.264..7.26578341
F2: 3,4                                  # 20 pairs
* PAIR I2: 3,8 BLK 3
H1: 3,8,1,2,7                            # reduction candidate for 3,8
H1: 3,8                                  # 24 pairs
I1: 3,8,2                                # reduction candidate for 3,8
I1: 3,8                                  # 19 pairs
H2: 3,8,1,7                              # reduction candidate for 3,8
H2: 3,8                                  # 22 pairs
* PAIR C4: 5,7 COL C
C1: 5,7,8,9                              # reduction candidate for 5,7
C1: 5,7 => SOLVED
* 967513428852964713134782659275396184681427935493851276748139562316245897529678341
C1: 8,9                                  # 20 pairs
C7: 5,7,6,8                              # reduction candidate for 5,7
C7: 5,7                                  # 28 pairs
* PAIR F5: 5,7 BLK 5
F6: 5,7,1                                # reduction candidate for 5,7
F6: 5,7 => CTR
* .6.95.4..9.2......1347826592..396..468142....49381.2...4.139...31.2....7.2.578341
F6: 1                                    # 21 pairs
* PAIR F5: 5,7 ROW 5
G5: 5,7,9                                # reduction candidate for 5,7
G5: 9                                    # 24 pairs
G5: 5,7                                  # 22 pairs
* PAIR E6: 1,5 BLK 5
F6: 1,5,7                                # reduction candidate for 1,5
F6: 7 => CTR
* .6.95.4.29.2.....81347826592..396..4681425..3493817265.4.139.2631.2.4..7.2.578341
F6: 1,5                                  # 22 pairs
* PAIR G4: 1,8 COL G
G2: 1,8,7                                # reduction candidate for 1,8
G2: 1,8 => CTR
* .6..5.4.2..2.....81347826592..396814681425793493817265.4.139526315264987926578341
G2: 7                                    # 22 pairs
* PAIR H4: 1,8 COL H
H1: 1,8,2,3,7                            # reduction candidate for 1,8
H1: 1,8                                  # 24 pairs
H2: 1,8,3,7                              # reduction candidate for 1,8
H2: 1,8                                  # 22 pairs
* PAIR I6: 5,6 COL I
I7: 5,6,2,8                              # reduction candidate for 5,6
I7: 5,6                                  # 20 pairs
I7: 2,8                                  # 19 pairs
* PAIR A9: 5,9 BLK 7
C9: 5,9,6                                # reduction candidate for 5,9
C9: 5,9 => SOLVED
* 967513428852964713134782659275396184681427935493851276748139562316245897529678341
C9: 6 => CTR
* .695134....2964...1347826592..396..468142....493851276.4.139...31.245..7.2..78341
* PAIR A9: 5,9 COL A
A1: 5,9,7,8                              # reduction candidate for 5,9
A1: 5,9 => SOLVED
* 967513428852964713134782659275396184681427935493851276748139562316245897529678341
A1: 7,8                                  # 20 pairs
A2: 5,9,7,8                              # reduction candidate for 5,9
A2: 5,9                                  # 23 pairs
* PAIR F8: 4,5 COL F
F2: 4,5,1,3                              # reduction candidate for 4,5
F2: 4,5 => SOLVED
* 967513428852964713134782659275396184681427935493851276748139562316245897529678341
F2: 1,3 => CTR
* .69...4....2.4....1347826592..396..468142....4938..2...4.139...31.264..7.26578341
* PAIR D9: 5,6 ROW 9
C9: 5,6,9                                # reduction candidate for 5,6
C9: 5,6 => CTR
* 7695134....2964...1347826592..396..468142....493851276.4.139...31.245..7925678341
C9: 9 => SOLVED
* 967513428852964713134782659275396184681427935493851276748139562316245897529678341
* PAIR D9: 5,6 COL D
D2: 5,6,9                                # reduction candidate for 5,6
D2: 5,6 => CTR
* .6.9..4..9.2564...134782659257396..468142....49385127674.139...31.245..7529678341
D2: 9 => SOLVED
* 967513428852964713134782659275396184681427935493851276748139562316245897529678341
* PAIR G7: 5,8 BLK 9
I7: 5,8,2,6                              # reduction candidate for 5,8
I7: 5,8 => CTR
* .6...34.2..2.647..1347826592..396..468142..934938..276.46139.2531.245967.2.678341
I7: 2,6                                  # 22 pairs
G8: 5,8,9                                # reduction candidate for 5,8
G8: 5,8                                  # 24 pairs
* PAIR G7: 5,8 ROW 7
A7: 5,8,7                                # reduction candidate for 5,8
A7: 5,8                                  # 26 pairs
C7: 5,8,6,7                              # reduction candidate for 5,8
C7: 5,8                                  # 25 pairs
* INCONCLUSIVE
* SAVE PR GRAPH zz-www.sudokuoftheday.co.uk-20190304-absurd-base-pr-000.dot
* REASONING
* PRF # C1: 5,7 => SOL
* DIS # A2: 5,7 => CTR => A2: 8,9
* PRF # D2: 5,9 => SOL
* DIS # D2: 6 => CTR => D2: 5,9
* PRF # A1: 5,9 => SOL
* DIS # C1: 5,9 => CTR => C1: 7,8
* PRF # C1: 7,8 => SOL
* DIS # F1: 1,5 => CTR => F1: 3
* DIS # F2: 1,5 => CTR => F2: 3,4
* PRF # C1: 5,7 => SOL
* DIS # F6: 5,7 => CTR => F6: 1
* DIS # F6: 7 => CTR => F6: 1,5
* DIS # G2: 1,8 => CTR => G2: 7
* PRF # C9: 5,9 => SOL
* DIS # C9: 6 => CTR => C9: 5,9
* PRF # A1: 5,9 => SOL
* PRF # F2: 4,5 => SOL
* DIS # F2: 1,3 => CTR => F2: 4,5
* DIS # C9: 5,6 => CTR => C9: 9
* PRF # C9: 9 => SOL
* DIS # D2: 5,6 => CTR => D2: 9
* PRF # D2: 9 => SOL
* DIS # I7: 5,8 => CTR => I7: 2,6
* CNT  23 HDP CHAINS /  49 HYP OPENED

--------------------------------------------------
* PREPARE PR GRAPH
* PAIR REDUCTION ..
* LEVEL 0 PASS 1 ROUND 1 (AUTO SOLVE) (A9,B2,B4,C4,D1,D9,E1,E2,E6,E8,F5,F8,G4,G7,H4,H6,I2,I5,I6)
* .6....4....2......1347826592..396..468142....4938..2...4.139...31.2....7.2..78341
* PAIR B2: 5,7 BLK 1
A1: 5,7,8,9                              # reduction candidate for 5,7
A1: 5,7                                  # 22 pairs
C1: 5,7,8,9                              # reduction candidate for 5,7
C1: 5,7 => SOLVED
* 967513428852964713134782659275396184681427935493851276748139562316245897529678341
* DURATION: 0:00:02.961894  START: 04:14:45.976362  END: 04:14:48.938256 2019-05-01
* SOLUTION FOUND
* SAVE PR GRAPH zz-www.sudokuoftheday.co.uk-20190304-absurd-base-pr-001.dot
* REASONING
* PRF # C1: 5,7 => SOL
* STA C1: 5,7
* CNT   1 HDP CHAINS /   2 HYP OPENED

Header Info

http://www.sudokuoftheday.co.uk/cgi-bin/sudoku1280.cgi?ACTION=archive2&USER=&MONTH=Mar&YEAR=2019, 20190304, absurd

Solution

position: 967513428852964713134782659275396184681427935493851276748139562316245897529678341 solved
Solution

See section Pair Reduction for the HDP chains leading to this result.

Appendix: Full HDP Chains

A1. Pair Reduction Analysis

Full list of HDP chains traversed:

* INC # A1: 5,7 => UNS
* PRF # C1: 5,7 => SOL
* INC # C1: 8,9 => UNS
* DIS # A2: 5,7 => CTR => A2: 8,9
* INC # A2: 8,9 => UNS
* PRF # D2: 5,9 => SOL
* DIS # D2: 6 => CTR => D2: 5,9
* PRF # A1: 5,9 => SOL
* INC # A1: 7,8 => UNS
* DIS # C1: 5,9 => CTR => C1: 7,8
* PRF # C1: 7,8 => SOL
* DIS # F1: 1,5 => CTR => F1: 3
* INC # F1: 3 => UNS
* DIS # F2: 1,5 => CTR => F2: 3,4
* INC # F2: 3,4 => UNS
* INC # H1: 3,8 => UNS
* INC # I1: 3,8 => UNS
* INC # H2: 3,8 => UNS
* PRF # C1: 5,7 => SOL
* INC # C1: 8,9 => UNS
* INC # C7: 5,7 => UNS
* DIS # F6: 5,7 => CTR => F6: 1
* INC # F6: 1 => UNS
* INC # G5: 5,7 => UNS
* INC # G5: 9 => UNS
* INC # F6: 1,5 => UNS
* DIS # F6: 7 => CTR => F6: 1,5
* DIS # G2: 1,8 => CTR => G2: 7
* INC # G2: 7 => UNS
* INC # H1: 1,8 => UNS
* INC # H2: 1,8 => UNS
* INC # I7: 5,6 => UNS
* INC # I7: 2,8 => UNS
* PRF # C9: 5,9 => SOL
* DIS # C9: 6 => CTR => C9: 5,9
* PRF # A1: 5,9 => SOL
* INC # A1: 7,8 => UNS
* INC # A2: 5,9 => UNS
* PRF # F2: 4,5 => SOL
* DIS # F2: 1,3 => CTR => F2: 4,5
* DIS # C9: 5,6 => CTR => C9: 9
* PRF # C9: 9 => SOL
* DIS # D2: 5,6 => CTR => D2: 9
* PRF # D2: 9 => SOL
* DIS # I7: 5,8 => CTR => I7: 2,6
* INC # I7: 2,6 => UNS
* INC # G8: 5,8 => UNS
* INC # A7: 5,8 => UNS
* INC # C7: 5,8 => UNS
* CNT  49 HDP CHAINS /  49 HYP OPENED

A2. Pair Reduction

Full list of HDP chains traversed:

* INC # A1: 5,7 => UNS
* PRF # C1: 5,7 => SOL
* STA C1: 5,7
* CNT   2 HDP CHAINS /   2 HYP OPENED