Analysis of zz-www.sudokuoftheday.co.uk-20060819-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: 6...3589.5..9.......2..1...1....85.....2....1.3..57.84..........1..72.4.7..36.1.9 initial

Autosolve

position: 6.1.358925..926.1...2.81...1..6.85..8..2.3..1.3.157.84....19....1..72.4.7..3641.9 autosolve
Autosolve

Pair Reduction Variants

Pair Reduction Analysis

Pair Reduction Analysis

The following important HDP chains were detected:

* DIS # B2: 4,7 => CTR => B2: 8
* DIS # C2: 4,7 => CTR => C2: 3,8
* DIS # B3: 4,7 => CTR => B3: 9
* PRF # B4: 4,7 => SOL
* DIS # B4: 2,9 => CTR => B4: 4,7
* DIS # B5: 4,7 => CTR => B5: 5,6,9
* DIS # B3: 4,7 => CTR => B3: 9
* DIS # G3: 4,7 => CTR => G3: 3,6
* DIS # G2: 3,7 => CTR => G2: 4
* PRF # H3: 3,7 => SOL
* DIS # C2: 4,8 => CTR => C2: 3,7
* PRF # H3: 3,7 => SOL
* DIS # B4: 2,9 => CTR => B4: 4,7
* PRF # B4: 4,7 => SOL
* DIS # G6: 6 => CTR => G6: 2,9
* DIS # B5: 6,9 => CTR => B5: 4,5,7
* PRF # C5: 6,9 => SOL
* PRF # G6: 6,9 => SOL
* DIS # G6: 2 => CTR => G6: 6,9
* PRF # C8: 3,5 => SOL
* PRF # B4: 4,9 => SOL
* DIS # B5: 4,9 => CTR => B5: 5,6,7
* PRF # C5: 4,9 => SOL
* DIS # H4: 3,7 => CTR => H4: 2
* PRF # H4: 2 => SOL
* PRF # G5: 6,7 => SOL
* DIS # H3: 6,7 => CTR => H3: 3,5
* DIS # C8: 3,9 => CTR => C8: 5,6
* PRF # C8: 5,6 => SOL
* DIS # A3: 3,9 => CTR => A3: 4
* DIS # B9: 5,8 => CTR => B9: 2
* PRF # B9: 2 => SOL
* DIS # I7: 6 => CTR => I7: 5,8
* PRF # I8: 6 => SOL
* DIS # G7: 3,6 => CTR => G7: 2,7
* DIS # H7: 3,6 => CTR => H7: 2,5,7
* DIS # C8: 3,6 => CTR => C8: 5,9
* DIS # G3: 4,7 => CTR => G3: 3,6
* DIS # H7: 2,5 => CTR => H7: 3,6,7
* DIS # B9: 8 => CTR => B9: 2,5
* CNT  40 HDP CHAINS /  75 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 # B2: 4,7 => CTR => B2: 8
* DIS B2: 8 # C2: 4,7 => CTR => C2: 3
* DIS B2: 8 + C2: 3 # I8: 8 => CTR => I8: 5,6
* PRF B2: 8 + C2: 3 + I8: 5,6 # C5: 7,9 => SOL
* STA B2: 8 + C2: 3 + I8: 5,6 + C5: 7,9
* CNT   4 HDP CHAINS /   5 HYP OPENED

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

Details

Positions

6...3589.5..9.......2..1...1....85.....2....1.3..57.84..........1..72.4.7..36.1.9 initial
6.1.358925..926.1...2.81...1..6.85..8..2.3..1.3.157.84....19....1..72.4.7..3641.9 autosolve
671435892583926417492781635147698523859243761236157984364519278915872346728364159 solved

Classification

level: medium

Pairing Analysis

--------------------------------------------------
* PAIRS (17)
B1: 4,7
D1: 4,7
D3: 4,7
I2: 3,7
I3: 5,6
A6: 2,9
C6: 6,9
E4: 4,9
E5: 4,9
I4: 3,7
H5: 6,7
A8: 3,9
C9: 5,8
D7: 5,8
D8: 5,8
G8: 3,6
H9: 2,5

--------------------------------------------------
* CONSTRAINT PAIRS (AUTO SOLVE)
B4,A6: 2.. / B4 = 2  =>  0 pairs (X) / A6 = 2  =>  0 pairs (_)
H4,G6: 2.. / H4 = 2  =>  0 pairs (*) / G6 = 2  =>  0 pairs (X)
B4,H4: 2.. / B4 = 2  =>  0 pairs (X) / H4 = 2  =>  0 pairs (_)
A6,G6: 2.. / A6 = 2  =>  0 pairs (*) / G6 = 2  =>  0 pairs (X)
B9,H9: 2.. / B9 = 2  =>  0 pairs (*) / H9 = 2  =>  0 pairs (X)
A6,A7: 2.. / A6 = 2  =>  0 pairs (*) / A7 = 2  =>  0 pairs (X)
G6,G7: 2.. / G6 = 2  =>  0 pairs (X) / G7 = 2  =>  0 pairs (_)
C2,A3: 3.. / C2 = 3  => 22 pairs (_) / A3 = 3  =>  0 pairs (X)
H4,I4: 3.. / H4 = 3  =>  0 pairs (X) / I4 = 3  => 22 pairs (_)
I2,I4: 3.. / I2 = 3  =>  0 pairs (X) / I4 = 3  => 22 pairs (_)
D1,D3: 4.. / D1 = 4  => 16 pairs (_) / D3 = 4  =>  0 pairs (X)
G2,G3: 4.. / G2 = 4  => 18 pairs (_) / G3 = 4  =>  0 pairs (X)
E4,E5: 4.. / E4 = 4  =>  0 pairs (X) / E5 = 4  => 16 pairs (_)
B1,D1: 4.. / B1 = 4  =>  0 pairs (X) / D1 = 4  => 16 pairs (_)
A3,A7: 4.. / A3 = 4  => 22 pairs (_) / A7 = 4  =>  0 pairs (X)
H3,I3: 5.. / H3 = 5  =>  0 pairs (X) / I3 = 5  =>  0 pairs (_)
B5,C5: 5.. / B5 = 5  => 20 pairs (_) / C5 = 5  => 18 pairs (_)
D7,D8: 5.. / D7 = 5  => 16 pairs (_) / D8 = 5  => 16 pairs (_)
C6,G6: 6.. / C6 = 6  => 19 pairs (_) / G6 = 6  =>  0 pairs (X)
B5,B7: 6.. / B5 = 6  =>  0 pairs (X) / B7 = 6  => 19 pairs (_)
D1,D3: 7.. / D1 = 7  =>  0 pairs (X) / D3 = 7  => 16 pairs (_)
G7,H7: 7.. / G7 = 7  =>  0 pairs (X) / H7 = 7  => 23 pairs (_)
B1,D1: 7.. / B1 = 7  => 16 pairs (_) / D1 = 7  =>  0 pairs (X)
I2,I4: 7.. / I2 = 7  => 22 pairs (_) / I4 = 7  =>  0 pairs (X)
B2,C2: 8.. / B2 = 8  => 17 pairs (_) / C2 = 8  =>  0 pairs (X)
B9,C9: 8.. / B9 = 8  =>  0 pairs (X) / C9 = 8  => 17 pairs (_)
D7,D8: 8.. / D7 = 8  => 16 pairs (_) / D8 = 8  => 16 pairs (_)
I7,I8: 8.. / I7 = 8  => 16 pairs (_) / I8 = 8  => 16 pairs (_)
D7,I7: 8.. / D7 = 8  => 16 pairs (_) / I7 = 8  => 16 pairs (_)
D8,I8: 8.. / D8 = 8  => 16 pairs (_) / I8 = 8  => 16 pairs (_)
B2,B9: 8.. / B2 = 8  => 17 pairs (_) / B9 = 8  =>  0 pairs (X)
C2,C9: 8.. / C2 = 8  =>  0 pairs (X) / C9 = 8  => 17 pairs (_)
A3,B3: 9.. / A3 = 9  =>  0 pairs (X) / B3 = 9  => 18 pairs (_)
E4,E5: 9.. / E4 = 9  => 16 pairs (_) / E5 = 9  =>  0 pairs (X)
G5,G6: 9.. / G5 = 9  => 18 pairs (_) / G6 = 9  =>  0 pairs (*)
A8,C8: 9.. / A8 = 9  =>  0 pairs (*) / C8 = 9  =>  0 pairs (X)
* DURATION: 0:00:44.100606  START: 01:54:24.734193  END: 01:55:08.834799 2019-05-01
* CP COUNT: (36)
* SOLUTION FOUND

--------------------------------------------------
* PREPARE PR GRAPH
* PAIR REDUCTION ..
* LEVEL 0 PASS 1 ROUND 1 (AUTO SOLVE) (A6,A8,B1,C6,C9,D1,D3,D7,D8,E4,E5,G8,H5,H9,I2,I3,I4)
* 6.1.358925..926.1...2.81...1..6.85..8..2.3..1.3.157.84....19....1..72.4.7..3641.9
* PAIR B1: 4,7 BLK 1
B2: 4,7,8                                # reduction candidate for 4,7
B2: 4,7 => CTR
* 6.1.358925.8926.1.392.81...12.6.85..8..2.3..1.3.157.844...19...91..72.4.785364129
B2: 8                                    # 17 pairs
C2: 4,7,3,8                              # reduction candidate for 4,7
C2: 4,7 => CTR
* 6.1.3589258.926.1.392.81...1..6.85..8..2.3..123.157.844...1927.91..7234.728364159
C2: 3,8                                  # 18 pairs
B3: 4,7,9                                # reduction candidate for 4,7
B3: 4,7 => CTR
* 6.1.358925..926.1.9.2.81...1..6.85..8..2.3..123.157.844...1927.319.7264.728364159
B3: 9                                    # 18 pairs
* PAIR B1: 4,7 COL B
B4: 4,7,2,9                              # reduction candidate for 4,7
B4: 4,7 => SOLVED
* 671435892583926417492781635147698523859243761236157984364519278915872346728364159
B4: 2,9 => CTR
* 6.1.35892583926417..2.8135612.6985738..2.3.61.36157.84.6..19.3.319.7264.758364129
B5: 4,7,5,6,9                            # reduction candidate for 4,7
B5: 4,7 => CTR
* 6.1.3589258.926.1...2.81...12.6.85..8.52.3..1936157284264.19...319.7264.758364129
B5: 5,6,9                                # 17 pairs
* PAIR D3: 4,7 ROW 3
B3: 4,7,9                                # reduction candidate for 4,7
B3: 4,7 => CTR
* 6.1.358925..926.1.9.2.81...1..6.85..8..2.3..123.157.844...1927.319.7264.728364159
B3: 9                                    # 18 pairs
G3: 4,7,3,6                              # reduction candidate for 4,7
G3: 4,7 => CTR
* 6.1.358925..926.1.392.81...1..6.85..8..2.3..123.157.844...1927.91..7234.728364159
G3: 3,6                                  # 22 pairs
* PAIR I2: 3,7 BLK 3
G2: 3,7,4                                # reduction candidate for 3,7
G2: 3,7 => CTR
* 67143589258492671339278146.1..6.85..8..2.3..123.157.844...1927..1..7234.728364159
G2: 4                                    # 18 pairs
G3: 3,7,4,6                              # reduction candidate for 3,7
G3: 3,7                                  # 20 pairs
H3: 3,7,5,6                              # reduction candidate for 3,7
H3: 3,7 => SOLVED
* 671435892583926417492781635147698523859243761236157984364519278915872346728364159
H3: 5,6                                  # 18 pairs
* PAIR I2: 3,7 ROW 2
C2: 3,7,4,8                              # reduction candidate for 3,7
C2: 4,8 => CTR
* 6.1.358925..926.1.392.81...1..6.85..8..2.3..123.157.844...1927.91..7234.728364159
C2: 3,7                                  # 18 pairs
* PAIR I3: 5,6 BLK 3
H3: 5,6,3,7                              # reduction candidate for 5,6
H3: 3,7 => SOLVED
* 671435892583926417492781635147698523859243761236157984364519278915872346728364159
H3: 5,6                                  # 18 pairs
* PAIR I3: 5,6 COL I
I7: 5,6,8                                # reduction candidate for 5,6
I7: 5,6                                  # 16 pairs
I8: 5,6,8                                # reduction candidate for 5,6
I8: 5,6                                  # 16 pairs
* PAIR A6: 2,9 BLK 4
B4: 2,9,4,7                              # reduction candidate for 2,9
B4: 2,9 => CTR
* 6.1.35892583926417..2.8135612.6985738..2.3.61.36157.84.6..19.3.319.7264.758364129
B4: 4,7 => SOLVED
* 671435892583926417492781635147698523859243761236157984364519278915872346728364159
* PAIR A6: 2,9 ROW 6
G6: 2,9,6                                # reduction candidate for 2,9
G6: 6 => CTR
* 6.1.358925..926.1...2.81...1..6.85238..2.3971239157684....19....1..72.4.7..3641.9
G6: 2,9                                  # 19 pairs
* PAIR C6: 6,9 BLK 4
B5: 6,9,4,5,7                            # reduction candidate for 6,9
B5: 6,9 => CTR
* 6714358925839264174927816..1476985238.5243..123.157.84....1927..1..7234.728364159
B5: 4,5,7                                # 19 pairs
C5: 6,9,4,5,7                            # reduction candidate for 6,9
C5: 6,9 => SOLVED
* 671435892583926417492781635147698523859243761236157984364519278915872346728364159
C5: 4,5,7                                # 17 pairs
* PAIR C6: 6,9 ROW 6
G6: 6,9,2                                # reduction candidate for 6,9
G6: 6,9 => SOLVED
* 671435892583926417492781635147698523859243761236157984364519278915872346728364159
G6: 2 => CTR
* 6.1.358925..926.1.492781...12.6.85..8..2.3961.36157284264.19....1..72.4.7..364129
* PAIR C6: 6,9 COL C
C8: 6,9,3,5                              # reduction candidate for 6,9
C8: 3,5 => SOLVED
* 671435892583926417492781635147698523859243761236157984364519278915872346728364159
C8: 6,9                                  # 20 pairs
* PAIR E4: 4,9 ROW 4
B4: 4,9,2,7                              # reduction candidate for 4,9
B4: 4,9 => SOLVED
* 671435892583926417492781635147698523859243761236157984364519278915872346728364159
B4: 2,7                                  # 19 pairs
C4: 4,9,7                                # reduction candidate for 4,9
C4: 4,9                                  # 19 pairs
* PAIR E5: 4,9 ROW 5
B5: 4,9,5,6,7                            # reduction candidate for 4,9
B5: 4,9 => CTR
* 6.1.3589258.926.1...2.81...1276.85..8.52.3..1.36157.84.6..19....1..72.4.758364129
B5: 5,6,7                                # 17 pairs
C5: 4,9,5,6,7                            # reduction candidate for 4,9
C5: 4,9 => SOLVED
* 671435892583926417492781635147698523859243761236157984364519278915872346728364159
C5: 5,6,7                                # 17 pairs
* PAIR I4: 3,7 BLK 6
H4: 3,7,2                                # reduction candidate for 3,7
H4: 3,7 => CTR
* 6.1.358925..926.1...2.81...12.6.85..8..2.3..1936157284264.19...319.7264.7..364129
H4: 2 => SOLVED
* 671435892583926417492781635147698523859243761236157984364519278915872346728364159
* PAIR H5: 6,7 BLK 6
G5: 6,7,9                                # reduction candidate for 6,7
G5: 6,7 => SOLVED
* 671435892583926417492781635147698523859243761236157984364519278915872346728364159
G5: 9                                    # 18 pairs
* PAIR H5: 6,7 ROW 5
B5: 6,7,4,5,9                            # reduction candidate for 6,7
B5: 6,7                                  # 20 pairs
C5: 6,7,4,5,9                            # reduction candidate for 6,7
C5: 6,7                                  # 22 pairs
* PAIR H5: 6,7 COL H
H3: 6,7,3,5                              # reduction candidate for 6,7
H3: 6,7 => CTR
* 6.1.358925..926.13392.81..51..6.85378..2.3.61.36157284....19....1..7234.7..3641.9
H3: 3,5                                  # 18 pairs
H7: 6,7,2,3,5                            # reduction candidate for 6,7
H7: 6,7                                  # 21 pairs
* PAIR A8: 3,9 BLK 7
C8: 3,9,5,6                              # reduction candidate for 3,9
C8: 3,9 => CTR
* 6.1.358925..926.1.49278135612.6485.3845293.61.36157284264.19....1..7264.7..364129
C8: 5,6 => SOLVED
* 671435892583926417492781635147698523859243761236157984364519278915872346728364159
* PAIR A8: 3,9 COL A
A3: 3,9,4                                # reduction candidate for 3,9
A3: 3,9 => CTR
* 6.1.3589258.926.1.392.81.6.1..6.85..8..2.3..123.157.844...1927..1..7234.728364159
A3: 4                                    # 22 pairs
* PAIR C9: 5,8 BLK 7
B9: 5,8,2                                # reduction candidate for 5,8
B9: 5,8 => CTR
* 6.1.358925..926.1...2.81...12.6.85..8..2.3..1936157284264.19...319.7264.7..364129
B9: 2 => SOLVED
* 671435892583926417492781635147698523859243761236157984364519278915872346728364159
* PAIR D7: 5,8 ROW 7
I7: 5,8,6                                # reduction candidate for 5,8
I7: 6 => CTR
* 6.1.358925..926.1...2.81..51..6.85..865243971.39157684...819..6.165723487..3641.9
I7: 5,8                                  # 18 pairs
* PAIR D8: 5,8 ROW 8
I8: 5,8,6                                # reduction candidate for 5,8
I8: 6 => SOLVED
* 671435892583926417492781635147698523859243761236157984364519278915872346728364159
I8: 5,8                                  # 18 pairs
* PAIR G8: 3,6 BLK 9
G7: 3,6,2,7                              # reduction candidate for 3,6
G7: 3,6 => CTR
* 6.1.358925..926.1.492781.5612.6.85378..2.39.1.3.1572842...19.7..1..72.4.7..364129
G7: 2,7                                  # 18 pairs
H7: 3,6,2,5,7                            # reduction candidate for 3,6
H7: 3,6 => CTR
* 6.1.358925..926.1...2.81.5612.6.85..8..2.3..1936157284264.1973.319.7264.7..364129
H7: 2,5,7                                # 18 pairs
* PAIR G8: 3,6 ROW 8
C8: 3,6,5,9                              # reduction candidate for 3,6
C8: 3,6 => CTR
* 6.1.3589258.926.1..92.81..51..6.85238..2.3761236157.84....1927.91..7234.728364159
C8: 5,9                                  # 19 pairs
* PAIR G8: 3,6 COL G
G3: 3,6,4,7                              # reduction candidate for 3,6
G3: 4,7 => CTR
* 6.1.358925..926.1.392.81...1..6.85..8..2.3..123.157.844...1927.91..7234.728364159
G3: 3,6                                  # 22 pairs
* PAIR H9: 2,5 BLK 9
H7: 2,5,3,6,7                            # reduction candidate for 2,5
H7: 2,5 => CTR
* 6.1.358925..92641...2.816.51..6.85..8..2.3961.3615728426..197...1..7234.7..3641.9
H7: 3,6,7                                # 17 pairs
* PAIR H9: 2,5 ROW 9
B9: 2,5,8                                # reduction candidate for 2,5
B9: 8 => CTR
* 6.1.358925.8926.1.392.81...12.6.85..85.2.3..193.157.84....19....1..72.4.785364129
B9: 2,5                                  # 17 pairs
* INCONCLUSIVE
* SAVE PR GRAPH zz-www.sudokuoftheday.co.uk-20060819-absurd-base-pr-000.dot
* REASONING
* DIS # B2: 4,7 => CTR => B2: 8
* DIS # C2: 4,7 => CTR => C2: 3,8
* DIS # B3: 4,7 => CTR => B3: 9
* PRF # B4: 4,7 => SOL
* DIS # B4: 2,9 => CTR => B4: 4,7
* DIS # B5: 4,7 => CTR => B5: 5,6,9
* DIS # B3: 4,7 => CTR => B3: 9
* DIS # G3: 4,7 => CTR => G3: 3,6
* DIS # G2: 3,7 => CTR => G2: 4
* PRF # H3: 3,7 => SOL
* DIS # C2: 4,8 => CTR => C2: 3,7
* PRF # H3: 3,7 => SOL
* DIS # B4: 2,9 => CTR => B4: 4,7
* PRF # B4: 4,7 => SOL
* DIS # G6: 6 => CTR => G6: 2,9
* DIS # B5: 6,9 => CTR => B5: 4,5,7
* PRF # C5: 6,9 => SOL
* PRF # G6: 6,9 => SOL
* DIS # G6: 2 => CTR => G6: 6,9
* PRF # C8: 3,5 => SOL
* PRF # B4: 4,9 => SOL
* DIS # B5: 4,9 => CTR => B5: 5,6,7
* PRF # C5: 4,9 => SOL
* DIS # H4: 3,7 => CTR => H4: 2
* PRF # H4: 2 => SOL
* PRF # G5: 6,7 => SOL
* DIS # H3: 6,7 => CTR => H3: 3,5
* DIS # C8: 3,9 => CTR => C8: 5,6
* PRF # C8: 5,6 => SOL
* DIS # A3: 3,9 => CTR => A3: 4
* DIS # B9: 5,8 => CTR => B9: 2
* PRF # B9: 2 => SOL
* DIS # I7: 6 => CTR => I7: 5,8
* PRF # I8: 6 => SOL
* DIS # G7: 3,6 => CTR => G7: 2,7
* DIS # H7: 3,6 => CTR => H7: 2,5,7
* DIS # C8: 3,6 => CTR => C8: 5,9
* DIS # G3: 4,7 => CTR => G3: 3,6
* DIS # H7: 2,5 => CTR => H7: 3,6,7
* DIS # B9: 8 => CTR => B9: 2,5
* CNT  40 HDP CHAINS /  75 HYP OPENED

--------------------------------------------------
* PREPARE PR GRAPH
* PAIR REDUCTION ..
* LEVEL 0 PASS 1 ROUND 1 (AUTO SOLVE) (A6,A8,B1,C6,C9,D1,D3,D7,D8,E4,E5,G8,H5,H9,I2,I3,I4)
* 6.1.358925..926.1...2.81...1..6.85..8..2.3..1.3.157.84....19....1..72.4.7..3641.9
* PAIR B1: 4,7 BLK 1
B2: 4,7,8                                # reduction candidate for 4,7
B2: 4,7 => CTR
* 6.1.358925.8926.1.392.81...12.6.85..8..2.3..1.3.157.844...19...91..72.4.785364129
C2: 4,7,3                                # reduction candidate for 4,7
C2: 4,7 => CTR
* 6.1.3589258.926.1.392.81...1..6.85..8..2.3..123.157.844...1927.91..7234.728364159
* PAIR I3: 5,6 COL I
I8: 5,6,8                                # reduction candidate for 5,6
I8: 8 => CTR
* 67143589258392641749278135612.64857384.2.3.61.36157.84.64.19..5.1.572648758364129
* PAIR RESTART

* LEVEL 0 PASS 1 ROUND 2 (AUTO SOLVE) (A6,A7,A8,B4,B5,B9,C4,C8,E4,E5,G3,G5,G6,G7,G8,H3,H4,H9,I3,I8)
* 671435892583926417492781...1..6.85.38..2.3.61.36157.84.64519..8.1.872.4.7.83641.9
* PAIR C4: 7,9 BLK 4
C5: 7,9,5                                # reduction candidate for 7,9
C5: 7,9 => SOLVED
* 671435892583926417492781635147698523859243761236157984364519278915872346728364159
* DURATION: 0:00:05.786453  START: 01:56:02.021009  END: 01:56:07.807462 2019-05-01
* SOLUTION FOUND
* SAVE PR GRAPH zz-www.sudokuoftheday.co.uk-20060819-absurd-base-pr-001.dot
* REASONING
* DIS # B2: 4,7 => CTR => B2: 8
* DIS B2: 8 # C2: 4,7 => CTR => C2: 3
* DIS B2: 8 + C2: 3 # I8: 8 => CTR => I8: 5,6
* PRF B2: 8 + C2: 3 + I8: 5,6 # C5: 7,9 => SOL
* STA B2: 8 + C2: 3 + I8: 5,6 + C5: 7,9
* CNT   4 HDP CHAINS /   5 HYP OPENED

Header Info

http://www.sudokuoftheday.co.uk/cgi-bin/sudoku1280.cgi?ACTION=archive2&USER=&MONTH=Aug&YEAR=2006, 20060819, absurd

Solution

position: 671435892583926417492781635147698523859243761236157984364519278915872346728364159 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:

* DIS # B2: 4,7 => CTR => B2: 8
* INC # B2: 8 => UNS
* DIS # C2: 4,7 => CTR => C2: 3,8
* INC # C2: 3,8 => UNS
* DIS # B3: 4,7 => CTR => B3: 9
* INC # B3: 9 => UNS
* PRF # B4: 4,7 => SOL
* DIS # B4: 2,9 => CTR => B4: 4,7
* DIS # B5: 4,7 => CTR => B5: 5,6,9
* INC # B5: 5,6,9 => UNS
* DIS # B3: 4,7 => CTR => B3: 9
* INC # B3: 9 => UNS
* DIS # G3: 4,7 => CTR => G3: 3,6
* INC # G3: 3,6 => UNS
* DIS # G2: 3,7 => CTR => G2: 4
* INC # G2: 4 => UNS
* INC # G3: 3,7 => UNS
* PRF # H3: 3,7 => SOL
* INC # H3: 5,6 => UNS
* INC # C2: 3,7 => UNS
* DIS # C2: 4,8 => CTR => C2: 3,7
* INC # H3: 5,6 => UNS
* PRF # H3: 3,7 => SOL
* INC # I7: 5,6 => UNS
* INC # I8: 5,6 => UNS
* DIS # B4: 2,9 => CTR => B4: 4,7
* PRF # B4: 4,7 => SOL
* INC # G6: 2,9 => UNS
* DIS # G6: 6 => CTR => G6: 2,9
* DIS # B5: 6,9 => CTR => B5: 4,5,7
* INC # B5: 4,5,7 => UNS
* PRF # C5: 6,9 => SOL
* INC # C5: 4,5,7 => UNS
* PRF # G6: 6,9 => SOL
* DIS # G6: 2 => CTR => G6: 6,9
* INC # C8: 6,9 => UNS
* PRF # C8: 3,5 => SOL
* PRF # B4: 4,9 => SOL
* INC # B4: 2,7 => UNS
* INC # C4: 4,9 => UNS
* DIS # B5: 4,9 => CTR => B5: 5,6,7
* INC # B5: 5,6,7 => UNS
* PRF # C5: 4,9 => SOL
* INC # C5: 5,6,7 => UNS
* DIS # H4: 3,7 => CTR => H4: 2
* PRF # H4: 2 => SOL
* PRF # G5: 6,7 => SOL
* INC # G5: 9 => UNS
* INC # B5: 6,7 => UNS
* INC # C5: 6,7 => UNS
* DIS # H3: 6,7 => CTR => H3: 3,5
* INC # H3: 3,5 => UNS
* INC # H7: 6,7 => UNS
* DIS # C8: 3,9 => CTR => C8: 5,6
* PRF # C8: 5,6 => SOL
* DIS # A3: 3,9 => CTR => A3: 4
* INC # A3: 4 => UNS
* DIS # B9: 5,8 => CTR => B9: 2
* PRF # B9: 2 => SOL
* INC # I7: 5,8 => UNS
* DIS # I7: 6 => CTR => I7: 5,8
* INC # I8: 5,8 => UNS
* PRF # I8: 6 => SOL
* DIS # G7: 3,6 => CTR => G7: 2,7
* INC # G7: 2,7 => UNS
* DIS # H7: 3,6 => CTR => H7: 2,5,7
* INC # H7: 2,5,7 => UNS
* DIS # C8: 3,6 => CTR => C8: 5,9
* INC # C8: 5,9 => UNS
* INC # G3: 3,6 => UNS
* DIS # G3: 4,7 => CTR => G3: 3,6
* DIS # H7: 2,5 => CTR => H7: 3,6,7
* INC # H7: 3,6,7 => UNS
* INC # B9: 2,5 => UNS
* DIS # B9: 8 => CTR => B9: 2,5
* CNT  75 HDP CHAINS /  75 HYP OPENED

A2. Pair Reduction

Full list of HDP chains traversed:

* DIS # B2: 4,7 => CTR => B2: 8
* DIS B2: 8 # C2: 4,7 => CTR => C2: 3
* INC B2: 8 + C2: 3 # I8: 5,6 => UNS
* DIS B2: 8 + C2: 3 # I8: 8 => CTR => I8: 5,6
* PRF B2: 8 + C2: 3 + I8: 5,6 # C5: 7,9 => SOL
* STA B2: 8 + C2: 3 + I8: 5,6 + C5: 7,9
* CNT   5 HDP CHAINS /   5 HYP OPENED