Analysis of zz-www.sudokuoftheday.co.uk-20060326-absurd-base.sdk

Contents

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

level: medium

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

position: ......6......67.23...1.2..4.57.......2..3...569....2..5.6...1..2...8695...95.13.. initial

Autosolve

position: ..2...6..9...67.23.6.192..4.57.......2..3...569.7..2..5.6...1..2...86957..95.13.. autosolve
Autosolve

Pair Reduction Variants

Pair Reduction Analysis

Pair Reduction Analysis

The following important HDP chains were detected:

* DIS # C3: 5 => CTR => C3: 3,8
* DIS # A4: 1,4 => CTR => A4: 3,8
* DIS # F1: 4,5 => CTR => F1: 3
* DIS # E6: 1 => CTR => E6: 4,5
* DIS # D1: 3 => CTR => D1: 4,8
* DIS # B2: 4,8 => CTR => B2: 1
* DIS # C2: 4,8 => CTR => C2: 1,5
* DIS # I4: 1,9 => CTR => I4: 6,8
* DIS # G3: 7 => CTR => G3: 5,8
* DIS # C2: 1,4 => CTR => C2: 5,8
* DIS # G3: 7,8 => CTR => G3: 5
* DIS # H5: 7,8 => CTR => H5: 1,6,9
* DIS # A4: 4,8 => CTR => A4: 1,3
* DIS # A5: 4,8 => CTR => A5: 1
* DIS # G5: 4,8 => CTR => G5: 7
* DIS # C2: 4,8 => CTR => C2: 1,5
* DIS # D4: 6,9 => CTR => D4: 2
* DIS # H5: 1,7,8 => CTR => H5: 6,9
* DIS # G5: 4,8 => CTR => G5: 7
* DIS # A4: 4,8 => CTR => A4: 1,3
* PRF # I4: 1,8 => SOL
* DIS # H5: 1,8 => CTR => H5: 6,7,9
* DIS # H6: 1,8 => CTR => H6: 3
* DIS # B8: 3 => CTR => B8: 1,4
* DIS # C2: 1,4 => CTR => C2: 5,8
* DIS # D4: 6 => CTR => D4: 2,9
* DIS # F7: 9 => CTR => F7: 3,4
* DIS # B8: 1 => CTR => B8: 3,4
* DIS # D1: 3,4 => CTR => D1: 8
* PRF # H9: 4,8 => SOL
* DIS # H9: 6 => CTR => H9: 4,8
* DIS # B7: 4,8 => CTR => B7: 3,7
* DIS # I9: 2,8 => CTR => I9: 6
* PRF # I9: 6 => SOL
* CNT  34 HDP CHAINS /  70 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 # C3: 5 => CTR => C3: 3,8
* DIS C3: 3,8 # A4: 1 => CTR => A4: 3,8
* DIS C3: 3,8 + A4: 3,8 # I4: 1,9 => CTR => I4: 6,8
* PRF C3: 3,8 + A4: 3,8 + I4: 6,8 => SOL
* STA C3: 3,8 + A4: 3,8 + I4: 6,8
* CNT   4 HDP CHAINS /   7 HYP OPENED

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

Details

Positions

......6......67.23...1.2..4.57.......2..3...569....2..5.6...1..2...8695...95.13.. initial
..2...6..9...67.23.6.192..4.57.......2..3...569.7..2..5.6...1..2...86957..95.13.. autosolve
472853619915467823863192574357219468124638795698745231536974182241386957789521346 solved

Classification

level: medium

Pairing Analysis

--------------------------------------------------
* PAIRS (16)
A3: 3,8
E1: 4,5
D2: 4,8
H1: 1,9
I1: 1,9
G2: 5,8
H3: 7,8
C5: 4,8
D5: 6,9
G4: 4,8
I6: 1,8
C8: 1,4
D7: 2,9
D8: 3,4
H7: 4,8
I7: 2,8

--------------------------------------------------
* CONSTRAINT PAIRS (AUTO SOLVE)
B2,C2: 1.. / B2 = 1  => 16 pairs (_) / C2 = 1  =>  0 pairs (X)
H1,I1: 1.. / H1 = 1  => 15 pairs (_) / I1 = 1  =>  0 pairs (X)
A4,A5: 1.. / A4 = 1  =>  0 pairs (X) / A5 = 1  => 16 pairs (_)
E4,E6: 1.. / E4 = 1  => 18 pairs (_) / E6 = 1  =>  0 pairs (X)
B8,C8: 1.. / B8 = 1  =>  0 pairs (X) / C8 = 1  => 16 pairs (_)
A5,H5: 1.. / A5 = 1  => 16 pairs (_) / H5 = 1  =>  0 pairs (X)
B2,B8: 1.. / B2 = 1  => 16 pairs (_) / B8 = 1  =>  0 pairs (X)
C2,C8: 1.. / C2 = 1  =>  0 pairs (X) / C8 = 1  => 16 pairs (_)
D4,E4: 2.. / D4 = 2  => 18 pairs (_) / E4 = 2  =>  0 pairs (X)
I7,I9: 2.. / I7 = 2  => 16 pairs (_) / I9 = 2  =>  0 pairs (X)
E9,I9: 2.. / E9 = 2  => 16 pairs (_) / I9 = 2  =>  0 pairs (X)
D4,D7: 2.. / D4 = 2  => 18 pairs (_) / D7 = 2  =>  0 pairs (X)
A3,C3: 3.. / A3 = 3  =>  0 pairs (X) / C3 = 3  => 16 pairs (_)
D1,F1: 3.. / D1 = 3  =>  0 pairs (X) / F1 = 3  => 23 pairs (_)
A4,C6: 3.. / A4 = 3  => 16 pairs (_) / C6 = 3  =>  0 pairs (X)
H4,H6: 3.. / H4 = 3  =>  0 pairs (X) / H6 = 3  => 16 pairs (_)
B7,B8: 3.. / B7 = 3  => 23 pairs (_) / B8 = 3  =>  0 pairs (X)
F7,D8: 3.. / F7 = 3  =>  0 pairs (X) / D8 = 3  => 23 pairs (_)
A4,H4: 3.. / A4 = 3  => 16 pairs (_) / H4 = 3  =>  0 pairs (X)
C6,H6: 3.. / C6 = 3  =>  0 pairs (X) / H6 = 3  => 16 pairs (_)
B7,F7: 3.. / B7 = 3  => 23 pairs (_) / F7 = 3  =>  0 pairs (X)
B8,D8: 3.. / B8 = 3  =>  0 pairs (X) / D8 = 3  => 23 pairs (_)
A3,A4: 3.. / A3 = 3  =>  0 pairs (X) / A4 = 3  => 16 pairs (_)
C3,C6: 3.. / C3 = 3  => 16 pairs (_) / C6 = 3  =>  0 pairs (X)
D1,D8: 3.. / D1 = 3  =>  0 pairs (X) / D8 = 3  => 23 pairs (_)
F1,F7: 3.. / F1 = 3  => 23 pairs (_) / F7 = 3  =>  0 pairs (X)
G4,G5: 4.. / G4 = 4  => 18 pairs (_) / G5 = 4  =>  0 pairs (X)
H7,H9: 4.. / H7 = 4  => 18 pairs (_) / H9 = 4  =>  0 pairs (*)
C2,C3: 5.. / C2 = 5  => 18 pairs (_) / C3 = 5  =>  0 pairs (X)
E1,F1: 5.. / E1 = 5  => 17 pairs (_) / F1 = 5  =>  0 pairs (X)
G2,G3: 5.. / G2 = 5  =>  0 pairs (X) / G3 = 5  => 18 pairs (_)
E6,F6: 5.. / E6 = 5  =>  0 pairs (X) / F6 = 5  => 17 pairs (_)
C2,G2: 5.. / C2 = 5  => 18 pairs (_) / G2 = 5  =>  0 pairs (X)
C3,G3: 5.. / C3 = 5  =>  0 pairs (X) / G3 = 5  => 18 pairs (_)
E1,E6: 5.. / E1 = 5  => 17 pairs (_) / E6 = 5  =>  0 pairs (X)
F1,F6: 5.. / F1 = 5  =>  0 pairs (X) / F6 = 5  => 17 pairs (_)
D4,D5: 6.. / D4 = 6  =>  0 pairs (X) / D5 = 6  => 16 pairs (_)
H9,I9: 6.. / H9 = 6  =>  0 pairs (X) / I9 = 6  =>  0 pairs (_)
D5,H5: 6.. / D5 = 6  => 16 pairs (_) / H5 = 6  =>  0 pairs (X)
I4,I9: 6.. / I4 = 6  =>  0 pairs (X) / I9 = 6  =>  0 pairs (_)
A1,B1: 7.. / A1 = 7  => 18 pairs (_) / B1 = 7  => 20 pairs (_)
G3,H3: 7.. / G3 = 7  =>  0 pairs (X) / H3 = 7  => 17 pairs (_)
G5,H5: 7.. / G5 = 7  => 17 pairs (_) / H5 = 7  =>  0 pairs (X)
E7,E9: 7.. / E7 = 7  => 17 pairs (_) / E9 = 7  =>  0 pairs (X)
B7,E7: 7.. / B7 = 7  =>  0 pairs (X) / E7 = 7  => 17 pairs (_)
A1,A9: 7.. / A1 = 7  => 18 pairs (_) / A9 = 7  => 20 pairs (_)
G3,G5: 7.. / G3 = 7  =>  0 pairs (X) / G5 = 7  => 17 pairs (_)
H3,H5: 7.. / H3 = 7  => 17 pairs (_) / H5 = 7  =>  0 pairs (X)
D1,D2: 8.. / D1 = 8  => 24 pairs (_) / D2 = 8  =>  0 pairs (X)
H1,I1: 9.. / H1 = 9  =>  0 pairs (X) / I1 = 9  => 15 pairs (_)
D7,F7: 9.. / D7 = 9  => 18 pairs (_) / F7 = 9  =>  0 pairs (X)
I1,I4: 9.. / I1 = 9  => 15 pairs (_) / I4 = 9  =>  0 pairs (X)
* DURATION: 0:01:11.365666  START: 21:54:15.744375  END: 21:55:27.110041 2019-04-30
* CP COUNT: (52)
* SOLUTION FOUND

--------------------------------------------------
* PREPARE PR GRAPH
* PAIR REDUCTION ..
* LEVEL 0 PASS 1 ROUND 1 (AUTO SOLVE) (A3,C5,C8,D2,D5,D7,D8,E1,G2,G4,H1,H3,H7,I1,I6,I7)
* ..2...6..9...67.23.6.192..4.57.......2..3...569.7..2..5.6...1..2...86957..95.13..
* PAIR A3: 3,8 BLK 1
C3: 3,8,5                                # reduction candidate for 3,8
C3: 5 => CTR
* ..2...6199184675233651928748572194361246387956937452815.69.41..2.1.86957..95.136.
C3: 3,8                                  # 18 pairs
* PAIR A3: 3,8 COL A
A4: 3,8,1,4                              # reduction candidate for 3,8
A4: 1,4 => CTR
* ..2...6919...67.2336.192..4.5721..3..2..39..56937..2..5.69..1..2...86957..95.13..
A4: 3,8                                  # 19 pairs
* PAIR E1: 4,5 BLK 2
F1: 4,5,3                                # reduction candidate for 4,5
F1: 4,5 => CTR
* ..23..619914867523365192.74.572.9836.2863..956937..2..5.69.31..231486957..95.136.
F1: 3                                    # 23 pairs
* PAIR E1: 4,5 COL E
E6: 4,5,1                                # reduction candidate for 4,5
E6: 1 => CTR
* ..2.5.6..9...67.23.6.192..4.57.......2..3...569.7152.85.6...1.22...86957..95213.6
E6: 4,5                                  # 18 pairs
* PAIR D2: 4,8 BLK 2
D1: 4,8,3                                # reduction candidate for 4,8
D1: 3 => CTR
* ..23..619914867523365192.74.572.9836.2863..956937..2..5.69.31..231486957..95.136.
D1: 4,8                                  # 23 pairs
* PAIR D2: 4,8 ROW 2
B2: 4,8,1                                # reduction candidate for 4,8
B2: 4,8 => CTR
* ..2.536..9.1.67523365192..4.57..843.428.397156937.52..536.7.1..214386957..95.13..
B2: 1                                    # 16 pairs
C2: 4,8,1,5                              # reduction candidate for 4,8
C2: 4,8 => CTR
* ..2...6199184675233651928748572194361246387956937452815.69.41..2.1.86957..95.136.
C2: 1,5                                  # 17 pairs
* PAIR H1: 1,9 COL H
H4: 1,9,3,6,8                            # reduction candidate for 1,9
H4: 1,9                                  # 19 pairs
H5: 1,9,6,7,8                            # reduction candidate for 1,9
H5: 1,9                                  # 19 pairs
* PAIR I1: 1,9 COL I
I4: 1,9,6,8                              # reduction candidate for 1,9
I4: 1,9 => CTR
* ..2...6..9...67.23.631925743572.846912.63...569.7..2385.697.1.22...86957..95213.6
I4: 6,8                                  # 17 pairs
* PAIR G2: 5,8 BLK 3
G3: 5,8,7                                # reduction candidate for 5,8
G3: 7 => CTR
* ..2...6..9...67523.65192784.57.......2..3..756937..218586.73142231486957..952136.
G3: 5,8                                  # 17 pairs
* PAIR G2: 5,8 ROW 2
C2: 5,8,1,4                              # reduction candidate for 5,8
C2: 1,4 => CTR
* ..2...6919...67523365192..4.5721..3..28.39..56937..2..5.69..1..2...86957..95.13..
C2: 5,8                                  # 19 pairs
* PAIR H3: 7,8 BLK 3
G3: 7,8,5                                # reduction candidate for 7,8
G3: 7,8 => CTR
* ..2...6199184675233651928748572194361246387956937452815.69.41..2.1.86957..95.136.
G3: 5                                    # 18 pairs
* PAIR H3: 7,8 COL H
H5: 7,8,1,6,9                            # reduction candidate for 7,8
H5: 7,8 => CTR
* ..2...6199...67.2386319257435721..9612.6397856987..2315.69..14.2..486957..95.136.
H5: 1,6,9                                # 17 pairs
* PAIR C5: 4,8 BLK 4
A4: 4,8,1,3                              # reduction candidate for 4,8
A4: 4,8 => CTR
* ..2...61991.467.2336.192.748572194361246387956937452815.69.41..2.1.86957..95.136.
A4: 1,3                                  # 17 pairs
A5: 4,8,1                                # reduction candidate for 4,8
A5: 4,8 => CTR
* ..2...6..9...67.23.6.192..4157....3..2..3..1569371.2..5.6...1..2...86957..95.13..
A5: 1                                    # 16 pairs
C6: 4,8,3                                # reduction candidate for 4,8
C6: 4,8                                  # 16 pairs
* PAIR C5: 4,8 ROW 5
F5: 4,8,9                                # reduction candidate for 4,8
F5: 4,8                                  # 22 pairs
G5: 4,8,7                                # reduction candidate for 4,8
G5: 4,8 => CTR
* ..2...6..9...67523365192784.57....3..2..3..7569.7..2..5.6...14.2...86957..95.136.
G5: 7                                    # 17 pairs
* PAIR C5: 4,8 COL C
C2: 4,8,1,5                              # reduction candidate for 4,8
C2: 4,8 => CTR
* ..2...6199184675233651928748572194361246387956937452815.69.41..2.1.86957..95.136.
C2: 1,5                                  # 17 pairs
* PAIR D5: 6,9 BLK 5
D4: 6,9,2                                # reduction candidate for 6,9
D4: 6,9 => CTR
* ..2...6..9...67.23.6.192..4.57.2.....2..3...569.7152.85.62..1..2...86957..95.13..
D4: 2                                    # 18 pairs
* PAIR D5: 6,9 ROW 5
H5: 6,9,1,7,8                            # reduction candidate for 6,9
H5: 1,7,8 => CTR
* ..2...6199...67.2386319257435721..9612.6397856987..2315.69..14.2..486957..95.136.
H5: 6,9                                  # 22 pairs
* PAIR G4: 4,8 BLK 6
G5: 4,8,7                                # reduction candidate for 4,8
G5: 4,8 => CTR
* ..2...6..9...67523365192784.57....3..2..3..7569.7..2..5.6...14.2...86957..95.136.
G5: 7                                    # 17 pairs
* PAIR G4: 4,8 ROW 4
A4: 4,8,1,3                              # reduction candidate for 4,8
A4: 4,8 => CTR
* ..2...61991.467.2336.192.748572194361246387956937452815.69.41..2.1.86957..95.136.
A4: 1,3                                  # 17 pairs
F4: 4,8,9                                # reduction candidate for 4,8
F4: 4,8                                  # 19 pairs
* PAIR I6: 1,8 BLK 6
H4: 1,8,3,6,9                            # reduction candidate for 1,8
H4: 1,8                                  # 20 pairs
I4: 1,8,6,9                              # reduction candidate for 1,8
I4: 1,8 => SOLVED
* 472853619915467823863192574357219468124638795698745231536974182241386957789521346
I4: 6,9                                  # 17 pairs
H5: 1,8,6,7,9                            # reduction candidate for 1,8
H5: 1,8 => CTR
* ..2...6199154678238631925743572184961246397856987.42315.69.314.2.1.86957..95.136.
H5: 6,7,9                                # 16 pairs
H6: 1,8,3                                # reduction candidate for 1,8
H6: 1,8 => CTR
* ..2...61991.467.2336.192.748572194361246387956937452815.69.41..2.1.86957..95.136.
H6: 3                                    # 16 pairs
* PAIR C8: 1,4 BLK 7
B8: 1,4,3                                # reduction candidate for 1,4
B8: 3 => CTR
* ..23..619914867523365192.74.572.9836.2863..956937..2..5.69.31..231486957..95.136.
B8: 1,4                                  # 23 pairs
* PAIR C8: 1,4 COL C
C2: 1,4,5,8                              # reduction candidate for 1,4
C2: 1,4 => CTR
* ..2...6919...67523365192..4.5721..3..28.39..56937..2..5.69..1..2...86957..95.13..
C2: 5,8                                  # 19 pairs
* PAIR D7: 2,9 COL D
D4: 2,9,6                                # reduction candidate for 2,9
D4: 6 => CTR
* ..2...6..9...67.23.6.192..4.5762.....2.93..6569.7152.85.6...1..2...86957..95.13..
D4: 2,9                                  # 16 pairs
* PAIR D8: 3,4 BLK 8
F7: 3,4,9                                # reduction candidate for 3,4
F7: 9 => CTR
* ..2..36..9...67.23.6.192..4.57.......2..3...569.7.52..536.791482..386957..9541362
F7: 3,4                                  # 18 pairs
* PAIR D8: 3,4 ROW 8
B8: 3,4,1                                # reduction candidate for 3,4
B8: 1 => CTR
* ..2.536..9.1.67523365192..4.57..843.428.397156937.52..536.7.1..214386957..95.13..
B8: 3,4                                  # 16 pairs
* PAIR D8: 3,4 COL D
D1: 3,4,8                                # reduction candidate for 3,4
D1: 3,4 => CTR
* ..2...6919..867523365192..4.5721..3..28.39..56937..2..5.69..1..2...86957..95.13..
D1: 8                                    # 24 pairs
* PAIR H7: 4,8 BLK 9
H9: 4,8,6                                # reduction candidate for 4,8
H9: 4,8 => SOLVED
* 472853619915467823863192574357219468124638795698745231536974182241386957789521346
H9: 6 => CTR
* ..23..619914867523.65192..445721.83612.63...569.7..2.15.69.314.231486957..95.136.
* PAIR H7: 4,8 ROW 7
B7: 4,8,3,7                              # reduction candidate for 4,8
B7: 4,8 => CTR
* 8723..619914867523365192.74.572.9836.2863..956937..2..5.69731.2231486957..9521368
B7: 3,7                                  # 19 pairs
* PAIR I7: 2,8 BLK 9
I9: 2,8,6                                # reduction candidate for 2,8
I9: 2,8 => CTR
* ..23..619914867523.65192..445721.83612.63...569.7..2.15.69.314.231486957..95.136.
I9: 6 => SOLVED
* 472853619915467823863192574357219468124638795698745231536974182241386957789521346
* INCONCLUSIVE
* SAVE PR GRAPH zz-www.sudokuoftheday.co.uk-20060326-absurd-base-pr-000.dot
* REASONING
* DIS # C3: 5 => CTR => C3: 3,8
* DIS # A4: 1,4 => CTR => A4: 3,8
* DIS # F1: 4,5 => CTR => F1: 3
* DIS # E6: 1 => CTR => E6: 4,5
* DIS # D1: 3 => CTR => D1: 4,8
* DIS # B2: 4,8 => CTR => B2: 1
* DIS # C2: 4,8 => CTR => C2: 1,5
* DIS # I4: 1,9 => CTR => I4: 6,8
* DIS # G3: 7 => CTR => G3: 5,8
* DIS # C2: 1,4 => CTR => C2: 5,8
* DIS # G3: 7,8 => CTR => G3: 5
* DIS # H5: 7,8 => CTR => H5: 1,6,9
* DIS # A4: 4,8 => CTR => A4: 1,3
* DIS # A5: 4,8 => CTR => A5: 1
* DIS # G5: 4,8 => CTR => G5: 7
* DIS # C2: 4,8 => CTR => C2: 1,5
* DIS # D4: 6,9 => CTR => D4: 2
* DIS # H5: 1,7,8 => CTR => H5: 6,9
* DIS # G5: 4,8 => CTR => G5: 7
* DIS # A4: 4,8 => CTR => A4: 1,3
* PRF # I4: 1,8 => SOL
* DIS # H5: 1,8 => CTR => H5: 6,7,9
* DIS # H6: 1,8 => CTR => H6: 3
* DIS # B8: 3 => CTR => B8: 1,4
* DIS # C2: 1,4 => CTR => C2: 5,8
* DIS # D4: 6 => CTR => D4: 2,9
* DIS # F7: 9 => CTR => F7: 3,4
* DIS # B8: 1 => CTR => B8: 3,4
* DIS # D1: 3,4 => CTR => D1: 8
* PRF # H9: 4,8 => SOL
* DIS # H9: 6 => CTR => H9: 4,8
* DIS # B7: 4,8 => CTR => B7: 3,7
* DIS # I9: 2,8 => CTR => I9: 6
* PRF # I9: 6 => SOL
* CNT  34 HDP CHAINS /  70 HYP OPENED

--------------------------------------------------
* PREPARE PR GRAPH
* PAIR REDUCTION ..
* LEVEL 0 PASS 1 ROUND 1 (AUTO SOLVE) (A3,C5,C8,D2,D5,D7,D8,E1,G2,G4,H1,H3,H7,I1,I6,I7)
* ..2...6..9...67.23.6.192..4.57.......2..3...569.7..2..5.6...1..2...86957..95.13..
* PAIR A3: 3,8 BLK 1
C3: 3,8,5                                # reduction candidate for 3,8
C3: 5 => CTR
* ..2...6199184675233651928748572194361246387956937452815.69.41..2.1.86957..95.136.
* PAIR A3: 3,8 COL A
A4: 3,8,1                                # reduction candidate for 3,8
A4: 1 => CTR
* 4728536..915467823368192574157.2.43.824.397.569.7.52..536.7.1..2413869577895.13..
* PAIR RESTART
* PAIR H1: 1,9 COL H
H4: 1,9,3,6,8                            # reduction candidate for 1,9
H4: 1,9                                  # 19 pairs
H4: 3,6,8                                # 18 pairs
* PAIR I1: 1,9 COL I
I4: 1,9,6,8                              # reduction candidate for 1,9
I4: 1,9 => CTR
* 4728536..915467823.6.192574.5721.46912.63978569.7.52..536.7.1.2241386957789521346
I4: 6,8 => SOLVED
* 472853619915467823863192574357219468124638795698745231536974182241386957789521346
* DURATION: 0:00:08.248875  START: 21:56:19.200585  END: 21:56:27.449460 2019-04-30
* SOLUTION FOUND
* SAVE PR GRAPH zz-www.sudokuoftheday.co.uk-20060326-absurd-base-pr-001.dot
* REASONING
* DIS # C3: 5 => CTR => C3: 3,8
* DIS C3: 3,8 # A4: 1 => CTR => A4: 3,8
* DIS C3: 3,8 + A4: 3,8 # I4: 1,9 => CTR => I4: 6,8
* PRF C3: 3,8 + A4: 3,8 + I4: 6,8 => SOL
* STA C3: 3,8 + A4: 3,8 + I4: 6,8
* CNT   4 HDP CHAINS /   7 HYP OPENED

Header Info

http://www.sudokuoftheday.co.uk/cgi-bin/sudoku1280.cgi?ACTION=archive2&USER=&MONTH=Mar&YEAR=2006, 20060326, absurd

Solution

position: 472853619915467823863192574357219468124638795698745231536974182241386957789521346 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 # C3: 3,8 => UNS
* DIS # C3: 5 => CTR => C3: 3,8
* INC # A4: 3,8 => UNS
* DIS # A4: 1,4 => CTR => A4: 3,8
* DIS # F1: 4,5 => CTR => F1: 3
* INC # F1: 3 => UNS
* INC # E6: 4,5 => UNS
* DIS # E6: 1 => CTR => E6: 4,5
* INC # D1: 4,8 => UNS
* DIS # D1: 3 => CTR => D1: 4,8
* DIS # B2: 4,8 => CTR => B2: 1
* INC # B2: 1 => UNS
* DIS # C2: 4,8 => CTR => C2: 1,5
* INC # C2: 1,5 => UNS
* INC # H4: 1,9 => UNS
* INC # H5: 1,9 => UNS
* DIS # I4: 1,9 => CTR => I4: 6,8
* INC # I4: 6,8 => UNS
* INC # G3: 5,8 => UNS
* DIS # G3: 7 => CTR => G3: 5,8
* INC # C2: 5,8 => UNS
* DIS # C2: 1,4 => CTR => C2: 5,8
* DIS # G3: 7,8 => CTR => G3: 5
* INC # G3: 5 => UNS
* DIS # H5: 7,8 => CTR => H5: 1,6,9
* INC # H5: 1,6,9 => UNS
* DIS # A4: 4,8 => CTR => A4: 1,3
* INC # A4: 1,3 => UNS
* DIS # A5: 4,8 => CTR => A5: 1
* INC # A5: 1 => UNS
* INC # C6: 4,8 => UNS
* INC # F5: 4,8 => UNS
* DIS # G5: 4,8 => CTR => G5: 7
* INC # G5: 7 => UNS
* DIS # C2: 4,8 => CTR => C2: 1,5
* INC # C2: 1,5 => UNS
* DIS # D4: 6,9 => CTR => D4: 2
* INC # D4: 2 => UNS
* INC # H5: 6,9 => UNS
* DIS # H5: 1,7,8 => CTR => H5: 6,9
* DIS # G5: 4,8 => CTR => G5: 7
* INC # G5: 7 => UNS
* DIS # A4: 4,8 => CTR => A4: 1,3
* INC # A4: 1,3 => UNS
* INC # F4: 4,8 => UNS
* INC # H4: 1,8 => UNS
* PRF # I4: 1,8 => SOL
* INC # I4: 6,9 => UNS
* DIS # H5: 1,8 => CTR => H5: 6,7,9
* INC # H5: 6,7,9 => UNS
* DIS # H6: 1,8 => CTR => H6: 3
* INC # H6: 3 => UNS
* INC # B8: 1,4 => UNS
* DIS # B8: 3 => CTR => B8: 1,4
* DIS # C2: 1,4 => CTR => C2: 5,8
* INC # C2: 5,8 => UNS
* INC # D4: 2,9 => UNS
* DIS # D4: 6 => CTR => D4: 2,9
* INC # F7: 3,4 => UNS
* DIS # F7: 9 => CTR => F7: 3,4
* INC # B8: 3,4 => UNS
* DIS # B8: 1 => CTR => B8: 3,4
* DIS # D1: 3,4 => CTR => D1: 8
* INC # D1: 8 => UNS
* PRF # H9: 4,8 => SOL
* DIS # H9: 6 => CTR => H9: 4,8
* DIS # B7: 4,8 => CTR => B7: 3,7
* INC # B7: 3,7 => UNS
* DIS # I9: 2,8 => CTR => I9: 6
* PRF # I9: 6 => SOL
* CNT  70 HDP CHAINS /  70 HYP OPENED

A2. Pair Reduction

Full list of HDP chains traversed:

* INC # C3: 3,8 => UNS
* DIS # C3: 5 => CTR => C3: 3,8
* INC C3: 3,8 # A4: 3,8 => UNS
* DIS C3: 3,8 # A4: 1 => CTR => A4: 3,8
* INC C3: 3,8 + A4: 3,8 # H4: 1,9 => UNS
* INC C3: 3,8 + A4: 3,8 # H4: 3,6,8 => UNS
* DIS C3: 3,8 + A4: 3,8 # I4: 1,9 => CTR => I4: 6,8
* PRF C3: 3,8 + A4: 3,8 + I4: 6,8 => SOL
* STA C3: 3,8 + A4: 3,8 + I4: 6,8
* CNT   8 HDP CHAINS /   7 HYP OPENED