Analysis of zz-www.sudokuoftheday.co.uk-20190415-absurd-base.sdk

Contents

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

level: medium

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

position: 736..1...914...7.5..5....1......85.....4.78.1...39........8.3....17..4...9.2...8. initial

Autosolve

position: 736541928914862735..5973614...6185.3...4278.11.83952.....18.3....17..4...9.2..18. autosolve
Autosolve

Pair Reduction Variants

Pair Reduction Analysis

Pair Reduction Analysis

The following important HDP chains were detected:

* DIS # B8: 5,6 => CTR => B8: 2,8
* PRF # A5: 5,6 => SOL
* DIS # A5: 3 => CTR => A5: 5,6
* PRF # B7: 5,6 => SOL
* DIS # B8: 5,6 => CTR => B8: 2,8
* PRF # H6: 6,7 => SOL
* PRF # B6: 4 => SOL
* DIS # B7: 2,7 => CTR => B7: 4,5,6
* DIS # C4: 2,7 => CTR => C4: 9
* PRF # C4: 9 => SOL
* DIS # A8: 3,5 => CTR => A8: 2,6,8
* DIS # F7: 4 => CTR => F7: 6,9
* PRF # A9: 3,5 => SOL
* DIS # A9: 4,6 => CTR => A9: 3,5
* DIS # F7: 9 => CTR => F7: 4,6
* DIS # A9: 4,6 => CTR => A9: 3,5
* PRF # A9: 3,5 => SOL
* DIS # H7: 5,6 => CTR => H7: 7
* PRF # H7: 7 => SOL
* DIS # B8: 5,6 => CTR => B8: 2,8
* DIS # H7: 5 => CTR => H7: 6,7
* CNT  21 HDP CHAINS /  39 HYP OPENED

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

Pair Reduction

Pair Reduction

The following important HDP chains were detected:

* DIS # B8: 5,6 => CTR => B8: 2,8
* PRF B8: 2,8 # A5: 5,6 => SOL
* STA B8: 2,8 + A5: 5,6
* CNT   2 HDP CHAINS /   7 HYP OPENED

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

Details

Positions

736..1...914...7.5..5....1......85.....4.78.1...39........8.3....17..4...9.2...8. initial
736541928914862735..5973614...6185.3...4278.11.83952.....18.3....17..4...9.2..18. autosolve
736541928914862735825973614279618543563427891148395267452186379681739452397254186 solved

Classification

level: medium

Pairing Analysis

--------------------------------------------------
* PAIRS (17)
A3: 2,8
B3: 2,8
A4: 2,4
B5: 5,6
C5: 3,9
H5: 6,9
I6: 6,7
C7: 2,7
C9: 3,7
E8: 3,5
F8: 6,9
E9: 3,5
F9: 4,6
I7: 2,9
H8: 5,6
I8: 2,9
I9: 6,7

--------------------------------------------------
* CONSTRAINT PAIRS (AUTO SOLVE)
A3,B3: 2.. / A3 = 2  => 18 pairs (_) / B3 = 2  => 16 pairs (_)
I7,I8: 2.. / I7 = 2  =>  0 pairs (X) / I8 = 2  => 15 pairs (_)
C4,C7: 2.. / C4 = 2  =>  0 pairs (X) / C7 = 2  => 15 pairs (_)
A5,C5: 3.. / A5 = 3  =>  0 pairs (X) / C5 = 3  =>  0 pairs (_)
E8,E9: 3.. / E8 = 3  => 15 pairs (_) / E9 = 3  =>  0 pairs (X)
A8,E8: 3.. / A8 = 3  =>  0 pairs (X) / E8 = 3  => 15 pairs (_)
C5,C9: 3.. / C5 = 3  =>  0 pairs (*) / C9 = 3  =>  0 pairs (X)
H4,H6: 4.. / H4 = 4  =>  0 pairs (*) / H6 = 4  =>  0 pairs (X)
F7,F9: 4.. / F7 = 4  =>  0 pairs (X) / F9 = 4  => 17 pairs (_)
B6,H6: 4.. / B6 = 4  =>  0 pairs (*) / H6 = 4  =>  0 pairs (X)
A9,F9: 4.. / A9 = 4  =>  0 pairs (X) / F9 = 4  => 17 pairs (_)
A5,B5: 5.. / A5 = 5  =>  0 pairs (*) / B5 = 5  =>  0 pairs (X)
E8,E9: 5.. / E8 = 5  =>  0 pairs (X) / E9 = 5  => 15 pairs (_)
H7,H8: 5.. / H7 = 5  =>  0 pairs (X) / H8 = 5  => 15 pairs (_)
A9,E9: 5.. / A9 = 5  =>  0 pairs (X) / E9 = 5  => 15 pairs (_)
I6,I9: 6.. / I6 = 6  =>  0 pairs (X) / I9 = 6  =>  0 pairs (_)
H7,I9: 7.. / H7 = 7  =>  0 pairs (*) / I9 = 7  =>  0 pairs (X)
C9,I9: 7.. / C9 = 7  =>  0 pairs (*) / I9 = 7  =>  0 pairs (X)
I6,I9: 7.. / I6 = 7  =>  0 pairs (*) / I9 = 7  =>  0 pairs (X)
A3,B3: 8.. / A3 = 8  => 16 pairs (_) / B3 = 8  => 18 pairs (_)
A8,B8: 8.. / A8 = 8  => 18 pairs (_) / B8 = 8  => 16 pairs (_)
A3,A8: 8.. / A3 = 8  => 16 pairs (_) / A8 = 8  => 18 pairs (_)
B3,B8: 8.. / B3 = 8  => 18 pairs (_) / B8 = 8  => 16 pairs (_)
C4,C5: 9.. / C4 = 9  =>  0 pairs (*) / C5 = 9  =>  0 pairs (X)
H4,H5: 9.. / H4 = 9  =>  0 pairs (X) / H5 = 9  =>  0 pairs (_)
F7,F8: 9.. / F7 = 9  =>  0 pairs (X) / F8 = 9  => 15 pairs (_)
I7,I8: 9.. / I7 = 9  => 15 pairs (_) / I8 = 9  =>  0 pairs (X)
C4,H4: 9.. / C4 = 9  =>  0 pairs (*) / H4 = 9  =>  0 pairs (X)
C5,H5: 9.. / C5 = 9  =>  0 pairs (X) / H5 = 9  =>  0 pairs (_)
F7,I7: 9.. / F7 = 9  =>  0 pairs (X) / I7 = 9  => 15 pairs (_)
F8,I8: 9.. / F8 = 9  => 15 pairs (_) / I8 = 9  =>  0 pairs (X)
* DURATION: 0:00:39.443373  START: 05:18:55.271902  END: 05:19:34.715275 2019-05-01
* CP COUNT: (31)
* SOLUTION FOUND

--------------------------------------------------
* PREPARE PR GRAPH
* PAIR REDUCTION ..
* LEVEL 0 PASS 1 ROUND 1 (AUTO SOLVE) (A3,A4,B3,B5,C5,C7,C9,E8,E9,F8,F9,H5,H8,I6,I7,I8,I9)
* 736541928914862735..5973614...6185.3...4278.11.83952.....18.3....17..4...9.2..18.
* PAIR A3: 2,8 COL A
A8: 2,8,3,5,6                            # reduction candidate for 2,8
A8: 2,8                                  # 21 pairs
A8: 3,5,6                                # 14 pairs
* PAIR B3: 2,8 COL B
B8: 2,8,5,6                              # reduction candidate for 2,8
B8: 5,6 => CTR
* 7365419289148627352859736144..6185.3...4278.11.839524..4218.3798.1739452.97254186
B8: 2,8                                  # 19 pairs
* PAIR A4: 2,4 BLK 4
B4: 2,4,7                                # reduction candidate for 2,4
B4: 7                                    # 20 pairs
B4: 2,4                                  # 18 pairs
* PAIR A4: 2,4 COL A
A7: 2,4,5,6                              # reduction candidate for 2,4
A7: 5,6                                  # 18 pairs
A7: 2,4                                  # 15 pairs
* PAIR B5: 5,6 BLK 4
A5: 5,6,3                                # reduction candidate for 5,6
A5: 5,6 => SOLVED
* 736541928914862735825973614279618543563427891148395267452186379681739452397254186
A5: 3 => CTR
* 736541928914862735..5973614...6185.3359427861168395247...18.37...173.45..9.2..18.
* PAIR B5: 5,6 COL B
B7: 5,6,2,4,7                            # reduction candidate for 5,6
B7: 5,6 => SOLVED
* 736541928914862735825973614279618543563427891148395267452186379681739452397254186
B7: 2,4,7                                # 17 pairs
B8: 5,6,2,8                              # reduction candidate for 5,6
B8: 5,6 => CTR
* 7365419289148627352859736144..6185.3...4278.11.839524..4218.3798.1739452.97254186
B8: 2,8                                  # 19 pairs
* PAIR I6: 6,7 BLK 6
H6: 6,7,4                                # reduction candidate for 6,7
H6: 6,7 => SOLVED
* 736541928914862735825973614279618543563427891148395267452186379681739452397254186
H6: 4                                    # 19 pairs
* PAIR I6: 6,7 ROW 6
B6: 6,7,4                                # reduction candidate for 6,7
B6: 4 => SOLVED
* 736541928914862735825973614279618543563427891148395267452186379681739452397254186
B6: 6,7                                  # 19 pairs
* PAIR C7: 2,7 BLK 7
B7: 2,7,4,5,6                            # reduction candidate for 2,7
B7: 2,7 => CTR
* 736541928914862735825973614247618593...4278.11.83952...7218.3.9.817.94.2.9325.187
B7: 4,5,6                                # 18 pairs
* PAIR C7: 2,7 COL C
C4: 2,7,9                                # reduction candidate for 2,7
C4: 2,7 => CTR
* 736541928914862735..5973614...618593..9427861168395247...18.37...17..45..9.2..18.
C4: 9 => SOLVED
* 736541928914862735825973614279618543563427891148395267452186379681739452397254186
* PAIR E8: 3,5 ROW 8
A8: 3,5,2,6,8                            # reduction candidate for 3,5
A8: 3,5 => CTR
* 736541928914862735825973614...6185.3...4278911.83952.6...18.359.817.9462.932..187
A8: 2,6,8                                # 15 pairs
* PAIR F8: 6,9 BLK 8
F7: 6,9,4                                # reduction candidate for 6,9
F7: 4 => CTR
* 736541928914862735..59736142..6185.3...4278.11.83952.6..21843.9..17394.2493256187
F7: 6,9                                  # 17 pairs
* PAIR E9: 3,5 ROW 9
A9: 3,5,4,6                              # reduction candidate for 3,5
A9: 3,5 => SOLVED
* 736541928914862735825973614279618543563427891148395267452186379681739452397254186
A9: 4,6 => CTR
* 736541928914862735..5973614...6185.33594278611.83952.....18.3....173.4...9325.187
* PAIR F9: 4,6 BLK 8
F7: 4,6,9                                # reduction candidate for 4,6
F7: 9 => CTR
* 736541928914862735..5973614..2618593..94278611683952476..1893.2..17.6459.9.25418.
F7: 4,6                                  # 15 pairs
* PAIR F9: 4,6 ROW 9
A9: 4,6,3,5                              # reduction candidate for 4,6
A9: 4,6 => CTR
* 736541928914862735..5973614...6185.33594278611.83952.....18.3....173.4...9325.187
A9: 3,5 => SOLVED
* 736541928914862735825973614279618543563427891148395267452186379681739452397254186
* PAIR H8: 5,6 BLK 9
H7: 5,6,7                                # reduction candidate for 5,6
H7: 5,6 => CTR
* 736541928914862735..5973614...6185.3...4278.11.83952.6...18.3....17..4...9325.187
H7: 7 => SOLVED
* 736541928914862735825973614279618543563427891148395267452186379681739452397254186
* PAIR H8: 5,6 ROW 8
A8: 5,6,2,3,8                            # reduction candidate for 5,6
A8: 5,6                                  # 13 pairs
B8: 5,6,2,8                              # reduction candidate for 5,6
B8: 5,6 => CTR
* 7365419289148627352859736144..6185.3...4278.11.839524..4218.3798.1739452.97254186
B8: 2,8                                  # 19 pairs
* PAIR I9: 6,7 BLK 9
H7: 6,7,5                                # reduction candidate for 6,7
H7: 5 => CTR
* 736541928914862735..5973614...6185.3...4278911.83952.6...18.35...17.9462.932..187
H7: 6,7                                  # 15 pairs
* INCONCLUSIVE
* SAVE PR GRAPH zz-www.sudokuoftheday.co.uk-20190415-absurd-base-pr-000.dot
* REASONING
* DIS # B8: 5,6 => CTR => B8: 2,8
* PRF # A5: 5,6 => SOL
* DIS # A5: 3 => CTR => A5: 5,6
* PRF # B7: 5,6 => SOL
* DIS # B8: 5,6 => CTR => B8: 2,8
* PRF # H6: 6,7 => SOL
* PRF # B6: 4 => SOL
* DIS # B7: 2,7 => CTR => B7: 4,5,6
* DIS # C4: 2,7 => CTR => C4: 9
* PRF # C4: 9 => SOL
* DIS # A8: 3,5 => CTR => A8: 2,6,8
* DIS # F7: 4 => CTR => F7: 6,9
* PRF # A9: 3,5 => SOL
* DIS # A9: 4,6 => CTR => A9: 3,5
* DIS # F7: 9 => CTR => F7: 4,6
* DIS # A9: 4,6 => CTR => A9: 3,5
* PRF # A9: 3,5 => SOL
* DIS # H7: 5,6 => CTR => H7: 7
* PRF # H7: 7 => SOL
* DIS # B8: 5,6 => CTR => B8: 2,8
* DIS # H7: 5 => CTR => H7: 6,7
* CNT  21 HDP CHAINS /  39 HYP OPENED

--------------------------------------------------
* PREPARE PR GRAPH
* PAIR REDUCTION ..
* LEVEL 0 PASS 1 ROUND 1 (AUTO SOLVE) (A3,A4,B3,B5,C5,C7,C9,E8,E9,F8,F9,H5,H8,I6,I7,I8,I9)
* 736541928914862735..5973614...6185.3...4278.11.83952.....18.3....17..4...9.2..18.
* PAIR A3: 2,8 COL A
A8: 2,8,3,5,6                            # reduction candidate for 2,8
A8: 2,8                                  # 21 pairs
A8: 3,5,6                                # 14 pairs
* PAIR B3: 2,8 COL B
B8: 2,8,5,6                              # reduction candidate for 2,8
B8: 5,6 => CTR
* 7365419289148627352859736144..6185.3...4278.11.839524..4218.3798.1739452.97254186
* PAIR RESTART
* PAIR A4: 2,4 COL A
A7: 2,4,5,6                              # reduction candidate for 2,4
A7: 5,6                                  # 20 pairs
A7: 2,4                                  # 15 pairs
* PAIR B5: 5,6 BLK 4
A5: 5,6,3                                # reduction candidate for 5,6
A5: 5,6 => SOLVED
* 736541928914862735825973614279618543563427891148395267452186379681739452397254186
* DURATION: 0:00:06.255122  START: 05:20:05.573472  END: 05:20:11.828594 2019-05-01
* SOLUTION FOUND
* SAVE PR GRAPH zz-www.sudokuoftheday.co.uk-20190415-absurd-base-pr-001.dot
* REASONING
* DIS # B8: 5,6 => CTR => B8: 2,8
* PRF B8: 2,8 # A5: 5,6 => SOL
* STA B8: 2,8 + A5: 5,6
* CNT   2 HDP CHAINS /   7 HYP OPENED

Header Info

http://www.sudokuoftheday.co.uk/cgi-bin/sudoku1280.cgi?ACTION=archive2&USER=&MONTH=Apr&YEAR=2019, 20190415, absurd

Solution

position: 736541928914862735825973614279618543563427891148395267452186379681739452397254186 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 # A8: 2,8 => UNS
* INC # A8: 3,5,6 => UNS
* INC # B8: 2,8 => UNS
* DIS # B8: 5,6 => CTR => B8: 2,8
* INC # B4: 2,4 => UNS
* INC # B4: 7 => UNS
* INC # A7: 2,4 => UNS
* INC # A7: 5,6 => UNS
* PRF # A5: 5,6 => SOL
* DIS # A5: 3 => CTR => A5: 5,6
* PRF # B7: 5,6 => SOL
* INC # B7: 2,4,7 => UNS
* DIS # B8: 5,6 => CTR => B8: 2,8
* INC # B8: 2,8 => UNS
* PRF # H6: 6,7 => SOL
* INC # H6: 4 => UNS
* INC # B6: 6,7 => UNS
* PRF # B6: 4 => SOL
* DIS # B7: 2,7 => CTR => B7: 4,5,6
* INC # B7: 4,5,6 => UNS
* DIS # C4: 2,7 => CTR => C4: 9
* PRF # C4: 9 => SOL
* DIS # A8: 3,5 => CTR => A8: 2,6,8
* INC # A8: 2,6,8 => UNS
* INC # F7: 6,9 => UNS
* DIS # F7: 4 => CTR => F7: 6,9
* PRF # A9: 3,5 => SOL
* DIS # A9: 4,6 => CTR => A9: 3,5
* INC # F7: 4,6 => UNS
* DIS # F7: 9 => CTR => F7: 4,6
* DIS # A9: 4,6 => CTR => A9: 3,5
* PRF # A9: 3,5 => SOL
* DIS # H7: 5,6 => CTR => H7: 7
* PRF # H7: 7 => SOL
* INC # A8: 5,6 => UNS
* DIS # B8: 5,6 => CTR => B8: 2,8
* INC # B8: 2,8 => UNS
* INC # H7: 6,7 => UNS
* DIS # H7: 5 => CTR => H7: 6,7
* CNT  39 HDP CHAINS /  39 HYP OPENED

A2. Pair Reduction

Full list of HDP chains traversed:

* INC # A8: 2,8 => UNS
* INC # A8: 3,5,6 => UNS
* INC # B8: 2,8 => UNS
* DIS # B8: 5,6 => CTR => B8: 2,8
* INC B8: 2,8 # A7: 2,4 => UNS
* INC B8: 2,8 # A7: 5,6 => UNS
* PRF B8: 2,8 # A5: 5,6 => SOL
* STA B8: 2,8 + A5: 5,6
* CNT   7 HDP CHAINS /   7 HYP OPENED