Analysis of zz-www.sudokuoftheday.co.uk-20060808-absurd-base.sdk

Contents

Sudoku from http://www.sudokuoftheday.co.uk/cgi-bin/sudoku1280.cgi?ACTION=archive2&USER=&MONTH=Aug&YEAR=2006

level: medium

Sudoku from http://www.sudokuoftheday.co.uk/cgi-bin/sudoku1280.cgi?ACTION=archive2&USER=&MONTH=Aug&YEAR=2006

position: ..6542.3.........49..3.........34.87.8..5...931..8.4.673........5..9.2.1......74. initial

Autosolve

position: 176542938.23.....494.3....2....34.87.8..5.3.931..8.4.673.4..895.5.793261...8.5743 autosolve
Autosolve

Pair Reduction Variants

Pair Reduction Analysis

Pair Reduction Analysis

The following important HDP chains were detected:

* DIS # D4: 2,9 => CTR => D4: 1,6
* DIS # C6: 2,9 => CTR => C6: 5,7
* DIS # C6: 2,5 => CTR => C6: 7,9
* DIS # C6: 2,5 => CTR => C6: 7,9
* DIS # A4: 2,6 => CTR => A4: 5
* PRF # A4: 5 => SOL
* PRF # A5: 2,6 => SOL
* DIS # A5: 4 => CTR => A5: 2,6
* PRF # F2: 1,6 => SOL
* DIS # F3: 1,6 => CTR => F3: 8
* PRF # F3: 8 => SOL
* DIS # F5: 1,6 => CTR => F5: 7
* PRF # F5: 7 => SOL
* CNT  13 HDP CHAINS /  34 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 # D4: 2,9 => CTR => D4: 1,6
* DIS D4: 1,6 # D5: 6 => CTR => D5: 1,2
* DIS D4: 1,6 + D5: 1,2 # C9: 1,2 => CTR => C9: 9
* PRF D4: 1,6 + D5: 1,2 + C9: 9 => SOL
* STA D4: 1,6 + D5: 1,2 + C9: 9
* CNT   4 HDP CHAINS /   8 HYP OPENED

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

Details

Positions

..6542.3.........49..3.........34.87.8..5...931..8.4.673........5..9.2.1......74. initial
176542938.23.....494.3....2....34.87.8..5.3.931..8.4.673.4..895.5.793261...8.5743 autosolve
176542938823961574945378612592634187684157329317289456731426895458793261269815743 solved

Classification

level: medium

Pairing Analysis

--------------------------------------------------
* PAIRS (15)
A2: 5,8
C3: 5,8
B4: 6,9
D6: 2,9
F6: 7,9
G4: 1,5
H5: 1,2
H6: 2,5
C7: 1,2
A8: 4,8
C8: 4,8
A9: 2,6
B9: 6,9
F7: 1,6
E9: 1,2

--------------------------------------------------
* CONSTRAINT PAIRS (AUTO SOLVE)
G4,H5: 1.. / G4 = 1  => 19 pairs (_) / H5 = 1  =>  0 pairs (X)
C7,C9: 1.. / C7 = 1  => 18 pairs (_) / C9 = 1  => 15 pairs (_)
D4,G4: 1.. / D4 = 1  =>  0 pairs (X) / G4 = 1  => 19 pairs (_)
C9,E9: 1.. / C9 = 1  => 15 pairs (_) / E9 = 1  => 18 pairs (_)
H5,H6: 2.. / H5 = 2  => 19 pairs (_) / H6 = 2  =>  0 pairs (X)
E7,E9: 2.. / E7 = 2  => 18 pairs (_) / E9 = 2  => 15 pairs (_)
C7,E7: 2.. / C7 = 2  => 15 pairs (_) / E7 = 2  => 18 pairs (_)
A5,C5: 4.. / A5 = 4  =>  0 pairs (X) / C5 = 4  =>  0 pairs (_)
A8,C8: 4.. / A8 = 4  =>  0 pairs (*) / C8 = 4  =>  0 pairs (X)
A5,A8: 4.. / A5 = 4  =>  0 pairs (X) / A8 = 4  =>  0 pairs (_)
C5,C8: 4.. / C5 = 4  =>  0 pairs (*) / C8 = 4  =>  0 pairs (X)
A2,C3: 5.. / A2 = 5  =>  0 pairs (X) / C3 = 5  =>  0 pairs (_)
G4,H6: 5.. / G4 = 5  =>  0 pairs (X) / H6 = 5  => 19 pairs (_)
C6,H6: 5.. / C6 = 5  =>  0 pairs (X) / H6 = 5  => 19 pairs (_)
A2,A4: 5.. / A2 = 5  =>  0 pairs (X) / A4 = 5  =>  0 pairs (_)
G2,G3: 6.. / G2 = 6  => 19 pairs (_) / G3 = 6  => 18 pairs (_)
A9,B9: 6.. / A9 = 6  => 17 pairs (_) / B9 = 6  => 17 pairs (_)
E7,F7: 6.. / E7 = 6  => 18 pairs (_) / F7 = 6  => 20 pairs (_)
B4,B9: 6.. / B4 = 6  => 17 pairs (_) / B9 = 6  => 17 pairs (_)
E2,E3: 7.. / E2 = 7  => 17 pairs (_) / E3 = 7  => 17 pairs (_)
H2,H3: 7.. / H2 = 7  => 17 pairs (_) / H3 = 7  => 17 pairs (_)
C5,C6: 7.. / C5 = 7  =>  0 pairs (X) / C6 = 7  =>  0 pairs (_)
F5,F6: 7.. / F5 = 7  =>  0 pairs (*) / F6 = 7  =>  0 pairs (X)
E2,H2: 7.. / E2 = 7  => 17 pairs (_) / H2 = 7  => 17 pairs (_)
E3,H3: 7.. / E3 = 7  => 17 pairs (_) / H3 = 7  => 17 pairs (_)
C5,F5: 7.. / C5 = 7  =>  0 pairs (X) / F5 = 7  =>  0 pairs (_)
C6,F6: 7.. / C6 = 7  =>  0 pairs (*) / F6 = 7  =>  0 pairs (X)
A2,C3: 8.. / A2 = 8  =>  0 pairs (*) / C3 = 8  =>  0 pairs (X)
F2,F3: 8.. / F2 = 8  =>  0 pairs (X) / F3 = 8  =>  0 pairs (_)
A8,C8: 8.. / A8 = 8  =>  0 pairs (X) / C8 = 8  =>  0 pairs (_)
A2,F2: 8.. / A2 = 8  =>  0 pairs (*) / F2 = 8  =>  0 pairs (X)
C3,F3: 8.. / C3 = 8  =>  0 pairs (X) / F3 = 8  =>  0 pairs (_)
A2,A8: 8.. / A2 = 8  =>  0 pairs (*) / A8 = 8  =>  0 pairs (X)
C3,C8: 8.. / C3 = 8  =>  0 pairs (X) / C8 = 8  =>  0 pairs (_)
D2,F2: 9.. / D2 = 9  =>  0 pairs (*) / F2 = 9  =>  0 pairs (X)
B9,C9: 9.. / B9 = 9  => 17 pairs (_) / C9 = 9  => 17 pairs (_)
B4,B9: 9.. / B4 = 9  => 17 pairs (_) / B9 = 9  => 17 pairs (_)
F2,F6: 9.. / F2 = 9  =>  0 pairs (X) / F6 = 9  =>  0 pairs (_)
* DURATION: 0:00:44.820532  START: 01:38:40.413554  END: 01:39:25.234086 2019-05-01
* CP COUNT: (38)
* SOLUTION FOUND

--------------------------------------------------
* PREPARE PR GRAPH
* PAIR REDUCTION ..
* LEVEL 0 PASS 1 ROUND 1 (AUTO SOLVE) (A2,A8,A9,B4,B9,C3,C7,C8,D6,E9,F6,F7,G4,H5,H6)
* 176542938.23.....494.3....2....34.87.8..5.3.931..8.4.673.4..895.5.793261...8.5743
* PAIR B4: 6,9 ROW 4
D4: 6,9,1,2                              # reduction candidate for 6,9
D4: 6,9                                  # 22 pairs
D4: 1,2                                  # 17 pairs
* PAIR D6: 2,9 BLK 5
D4: 2,9,1,6                              # reduction candidate for 2,9
D4: 2,9 => CTR
* 176542938.23.....494.3....2....34187487.5.32931..8745673.4..895854793261...8.5743
D4: 1,6                                  # 19 pairs
* PAIR D6: 2,9 ROW 6
C6: 2,9,5,7                              # reduction candidate for 2,9
C6: 2,9 => CTR
* 176542938.23..9..49483..5.2..5.34187487.5.32931..8745673.4..895854793261...8.5743
C6: 5,7                                  # 16 pairs
* PAIR F6: 7,9 ROW 6
C6: 7,9,2,5                              # reduction candidate for 7,9
C6: 2,5 => CTR
* 176542938.23..9..49483....2....34.87487.5.3.931.9874.673.4..895854793261...8.5743
C6: 7,9                                  # 22 pairs
* PAIR G4: 1,5 COL G
G2: 1,5,6                                # reduction candidate for 1,5
G2: 1,5                                  # 18 pairs
G3: 1,5,6                                # reduction candidate for 1,5
G3: 1,5                                  # 19 pairs
* PAIR H5: 1,2 ROW 5
D5: 1,2,6                                # reduction candidate for 1,2
D5: 1,2                                  # 20 pairs
D5: 6                                    # 18 pairs
* PAIR H6: 2,5 ROW 6
C6: 2,5,7,9                              # reduction candidate for 2,5
C6: 2,5 => CTR
* 176542938.23..9..49483....2....34.87487.5.3.931.9874.673.4..895854793261...8.5743
C6: 7,9                                  # 22 pairs
* PAIR C7: 1,2 BLK 7
C9: 1,2,9                                # reduction candidate for 1,2
C9: 9                                    # 17 pairs
C9: 1,2                                  # 17 pairs
* PAIR C7: 1,2 ROW 7
E7: 1,2,6                                # reduction candidate for 1,2
E7: 1,2                                  # 20 pairs
E7: 6                                    # 18 pairs
* PAIR A9: 2,6 COL A
A4: 2,6,5                                # reduction candidate for 2,6
A4: 2,6 => CTR
* 1765429385239.8..49483..5.2..5.34187482.573.931728945673.4..895854793261...8.5743
A4: 5 => SOLVED
* 176542938823961574945378612592634187684157329317289456731426895458793261269815743
A5: 2,6,4                                # reduction candidate for 2,6
A5: 2,6 => SOLVED
* 176542938823961574945378612592634187684157329317289456731426895458793261269815743
A5: 4 => CTR
* 1765429385239.8..49483..5.2..5.34187482.573.931728945673.4..895854793261...8.5743
* PAIR F7: 1,6 BLK 8
E7: 1,6,2                                # reduction candidate for 1,6
E7: 2                                    # 18 pairs
E7: 1,6                                  # 15 pairs
* PAIR F7: 1,6 COL F
F2: 1,6,8,9                              # reduction candidate for 1,6
F2: 1,6 => SOLVED
* 176542938823961574945378612592634187684157329317289456731426895458793261269815743
F2: 8,9                                  # 16 pairs
F3: 1,6,8                                # reduction candidate for 1,6
F3: 1,6 => CTR
* 1765429385239.8..49483..5.2..5.34187482.573.931728945673.4..895854793261...8.5743
F3: 8 => SOLVED
* 176542938823961574945378612592634187684157329317289456731426895458793261269815743
F5: 1,6,7                                # reduction candidate for 1,6
F5: 1,6 => CTR
* 176542938.23..9..49483....2....34.87487.5.3.931..874.673.4..895854793261...8.5743
F5: 7 => SOLVED
* 176542938823961574945378612592634187684157329317289456731426895458793261269815743
* PAIR E9: 1,2 BLK 8
E7: 1,2,6                                # reduction candidate for 1,2
E7: 1,2                                  # 20 pairs
E7: 6                                    # 18 pairs
* PAIR E9: 1,2 ROW 9
C9: 1,2,9                                # reduction candidate for 1,2
C9: 9                                    # 17 pairs
C9: 1,2                                  # 17 pairs
* INCONCLUSIVE
* SAVE PR GRAPH zz-www.sudokuoftheday.co.uk-20060808-absurd-base-pr-000.dot
* REASONING
* DIS # D4: 2,9 => CTR => D4: 1,6
* DIS # C6: 2,9 => CTR => C6: 5,7
* DIS # C6: 2,5 => CTR => C6: 7,9
* DIS # C6: 2,5 => CTR => C6: 7,9
* DIS # A4: 2,6 => CTR => A4: 5
* PRF # A4: 5 => SOL
* PRF # A5: 2,6 => SOL
* DIS # A5: 4 => CTR => A5: 2,6
* PRF # F2: 1,6 => SOL
* DIS # F3: 1,6 => CTR => F3: 8
* PRF # F3: 8 => SOL
* DIS # F5: 1,6 => CTR => F5: 7
* PRF # F5: 7 => SOL
* CNT  13 HDP CHAINS /  34 HYP OPENED

--------------------------------------------------
* PREPARE PR GRAPH
* PAIR REDUCTION ..
* LEVEL 0 PASS 1 ROUND 1 (AUTO SOLVE) (A2,A8,A9,B4,B9,C3,C7,C8,D6,E9,F6,F7,G4,H5,H6)
* 176542938.23.....494.3....2....34.87.8..5.3.931..8.4.673.4..895.5.793261...8.5743
* PAIR B4: 6,9 ROW 4
D4: 6,9,1,2                              # reduction candidate for 6,9
D4: 6,9                                  # 22 pairs
D4: 1,2                                  # 17 pairs
* PAIR D6: 2,9 BLK 5
D4: 2,9,1,6                              # reduction candidate for 2,9
D4: 2,9 => CTR
* 176542938.23.....494.3....2....34187487.5.32931..8745673.4..895854793261...8.5743
* PAIR G4: 1,5 COL G
G2: 1,5,6                                # reduction candidate for 1,5
G2: 1,5                                  # 22 pairs
G3: 1,5,6                                # reduction candidate for 1,5
G3: 1,5                                  # 23 pairs
* PAIR H5: 1,2 ROW 5
D5: 1,2,6                                # reduction candidate for 1,2
D5: 6 => CTR
* 176542938.23.....494.3....2....34.87.8.65.32931.28945673.4..895.5.793261...8.5743
* PAIR RESTART
* PAIR C7: 1,2 BLK 7
C9: 1,2,9                                # reduction candidate for 1,2
C9: 1,2 => CTR
* 176542938.23.....494.3....226913458748725631931598742673.461895854793261691825743
C9: 9 => SOLVED
* 176542938823961574945378612592634187684157329317289456731426895458793261269815743
* DURATION: 0:00:07.545234  START: 01:39:48.799272  END: 01:39:56.344506 2019-05-01
* SOLUTION FOUND
* SAVE PR GRAPH zz-www.sudokuoftheday.co.uk-20060808-absurd-base-pr-001.dot
* REASONING
* DIS # D4: 2,9 => CTR => D4: 1,6
* DIS D4: 1,6 # D5: 6 => CTR => D5: 1,2
* DIS D4: 1,6 + D5: 1,2 # C9: 1,2 => CTR => C9: 9
* PRF D4: 1,6 + D5: 1,2 + C9: 9 => SOL
* STA D4: 1,6 + D5: 1,2 + C9: 9
* CNT   4 HDP CHAINS /   8 HYP OPENED

Header Info

http://www.sudokuoftheday.co.uk/cgi-bin/sudoku1280.cgi?ACTION=archive2&USER=&MONTH=Aug&YEAR=2006, 20060808, absurd

Solution

position: 176542938823961574945378612592634187684157329317289456731426895458793261269815743 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 # D4: 6,9 => UNS
* INC # D4: 1,2 => UNS
* DIS # D4: 2,9 => CTR => D4: 1,6
* INC # D4: 1,6 => UNS
* DIS # C6: 2,9 => CTR => C6: 5,7
* INC # C6: 5,7 => UNS
* INC # C6: 7,9 => UNS
* DIS # C6: 2,5 => CTR => C6: 7,9
* INC # G2: 1,5 => UNS
* INC # G3: 1,5 => UNS
* INC # D5: 1,2 => UNS
* INC # D5: 6 => UNS
* DIS # C6: 2,5 => CTR => C6: 7,9
* INC # C6: 7,9 => UNS
* INC # C9: 1,2 => UNS
* INC # C9: 9 => UNS
* INC # E7: 1,2 => UNS
* INC # E7: 6 => UNS
* DIS # A4: 2,6 => CTR => A4: 5
* PRF # A4: 5 => SOL
* PRF # A5: 2,6 => SOL
* DIS # A5: 4 => CTR => A5: 2,6
* INC # E7: 1,6 => UNS
* INC # E7: 2 => UNS
* PRF # F2: 1,6 => SOL
* INC # F2: 8,9 => UNS
* DIS # F3: 1,6 => CTR => F3: 8
* PRF # F3: 8 => SOL
* DIS # F5: 1,6 => CTR => F5: 7
* PRF # F5: 7 => SOL
* INC # E7: 1,2 => UNS
* INC # E7: 6 => UNS
* INC # C9: 1,2 => UNS
* INC # C9: 9 => UNS
* CNT  34 HDP CHAINS /  34 HYP OPENED

A2. Pair Reduction

Full list of HDP chains traversed:

* INC # D4: 6,9 => UNS
* INC # D4: 1,2 => UNS
* DIS # D4: 2,9 => CTR => D4: 1,6
* INC D4: 1,6 # G2: 1,5 => UNS
* INC D4: 1,6 # G3: 1,5 => UNS
* INC D4: 1,6 # D5: 1,2 => UNS
* DIS D4: 1,6 # D5: 6 => CTR => D5: 1,2
* DIS D4: 1,6 + D5: 1,2 # C9: 1,2 => CTR => C9: 9
* PRF D4: 1,6 + D5: 1,2 + C9: 9 => SOL
* STA D4: 1,6 + D5: 1,2 + C9: 9
* CNT   9 HDP CHAINS /   8 HYP OPENED