Analysis of zz-www.sudokuoftheday.co.uk-20190128-absurd-base.sdk

Contents

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

level: medium

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

position: ....37....536...9.....29.85..5...9.......1...18..6..5..1.....4.7.6......2.9...8.. initial

Autosolve

position: 892537164453618.9.671429385365...9..924.516..18796.45.518..6.4.7.6...5..2.9..58.6 autosolve
Autosolve

Pair Reduction Variants

Pair Reduction Analysis

Pair Reduction Analysis

The following important HDP chains were detected:

* DIS # I4: 2,7 => CTR => I4: 1,8
* DIS # I7: 2,7 => CTR => I7: 3,9
* PRF # F8: 2,4 => SOL
* DIS # F8: 3 => CTR => F8: 2,4
* PRF # F8: 4 => SOL
* DIS # I5: 3,7 => CTR => I5: 8
* DIS # D5: 8 => CTR => D5: 3,7
* PRF # H9: 1 => SOL
* DIS # I8: 2,3 => CTR => I8: 1,9
* DIS # F8: 2 => CTR => F8: 3,4
* DIS # I7: 7,9 => CTR => I7: 2,3
* DIS # I7: 2,7 => CTR => I7: 3,9
* PRF # D7: 2,7 => SOL
* DIS # D7: 3 => CTR => D7: 2,7
* CNT  14 HDP CHAINS /  27 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 # I4: 2,7 => CTR => I4: 1,8
* DIS I4: 1,8 # I7: 2,7 => CTR => I7: 3,9
* PRF I4: 1,8 + I7: 3,9 # F8: 2,4 => SOL
* STA I4: 1,8 + I7: 3,9 + F8: 2,4
* CNT   3 HDP CHAINS /   3 HYP OPENED

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

Details

Positions

....37....536...9.....29.85..5...9.......1...18..6..5..1.....4.7.6......2.9...8.. initial
892537164453618.9.671429385365...9..924.516..18796.45.518..6.4.7.6...5..2.9..58.6 autosolve
892537164453618297671429385365842971924751638187963452518296743736184529249375816 solved

Classification

level: medium

Pairing Analysis

--------------------------------------------------
* PAIRS (11)
G2: 2,7
I2: 2,7
F4: 2,4
F6: 2,3
H5: 3,7
I6: 2,3
B8: 3,4
B9: 3,4
E7: 7,9
E9: 4,7
G7: 2,7

--------------------------------------------------
* CONSTRAINT PAIRS (AUTO SOLVE)
H4,I4: 1.. / H4 = 1  =>  0 pairs (X) / I4 = 1  => 15 pairs (_)
D8,D9: 1.. / D8 = 1  =>  0 pairs (*) / D9 = 1  =>  0 pairs (X)
D9,H9: 1.. / D9 = 1  => 14 pairs (_) / H9 = 1  =>  0 pairs (*)
I4,I8: 1.. / I4 = 1  => 15 pairs (_) / I8 = 1  =>  0 pairs (X)
G2,I2: 2.. / G2 = 2  => 13 pairs (_) / I2 = 2  =>  0 pairs (X)
F6,I6: 2.. / F6 = 2  =>  0 pairs (X) / I6 = 2  =>  0 pairs (_)
G2,G7: 2.. / G2 = 2  => 13 pairs (_) / G7 = 2  =>  0 pairs (X)
H4,H8: 2.. / H4 = 2  =>  0 pairs (X) / H8 = 2  =>  0 pairs (_)
D5,F6: 3.. / D5 = 3  =>  0 pairs (X) / F6 = 3  =>  0 pairs (_)
B8,B9: 3.. / B8 = 3  =>  0 pairs (*) / B9 = 3  =>  0 pairs (X)
F6,I6: 3.. / F6 = 3  =>  0 pairs (*) / I6 = 3  =>  0 pairs (X)
D7,I7: 3.. / D7 = 3  =>  0 pairs (X) / I7 = 3  =>  0 pairs (_)
F6,F8: 3.. / F6 = 3  =>  0 pairs (*) / F8 = 3  =>  0 pairs (X)
E4,F4: 4.. / E4 = 4  =>  0 pairs (*) / F4 = 4  =>  0 pairs (X)
B8,B9: 4.. / B8 = 4  => 12 pairs (_) / B9 = 4  =>  0 pairs (*)
B9,E9: 4.. / B9 = 4  =>  0 pairs (*) / E9 = 4  =>  0 pairs (X)
F4,F8: 4.. / F4 = 4  => 12 pairs (_) / F8 = 4  =>  0 pairs (*)
G2,I2: 7.. / G2 = 7  =>  0 pairs (X) / I2 = 7  => 13 pairs (_)
G2,G7: 7.. / G2 = 7  =>  0 pairs (X) / G7 = 7  => 13 pairs (_)
I4,I5: 8.. / I4 = 8  =>  0 pairs (X) / I5 = 8  => 12 pairs (_)
D8,E8: 8.. / D8 = 8  => 18 pairs (_) / E8 = 8  => 18 pairs (_)
D5,I5: 8.. / D5 = 8  =>  0 pairs (X) / I5 = 8  => 12 pairs (_)
E4,E8: 8.. / E4 = 8  => 18 pairs (_) / E8 = 8  => 18 pairs (_)
E7,E8: 9.. / E7 = 9  => 15 pairs (_) / E8 = 9  =>  0 pairs (X)
I7,I8: 9.. / I7 = 9  =>  0 pairs (X) / I8 = 9  => 15 pairs (_)
E7,I7: 9.. / E7 = 9  => 15 pairs (_) / I7 = 9  =>  0 pairs (X)
E8,I8: 9.. / E8 = 9  =>  0 pairs (X) / I8 = 9  => 15 pairs (_)
* DURATION: 0:00:33.882666  START: 03:16:41.985195  END: 03:17:15.867861 2019-05-01
* CP COUNT: (27)
* SOLUTION FOUND

--------------------------------------------------
* PREPARE PR GRAPH
* PAIR REDUCTION ..
* LEVEL 0 PASS 1 ROUND 1 (AUTO SOLVE) (B8,B9,E7,E9,F4,F6,G2,G7,H5,I2,I6)
* 892537164453618.9.671429385365...9..924.516..18796.45.518..6.4.7.6...5..2.9..58.6
* PAIR I2: 2,7 COL I
I4: 2,7,1,8                              # reduction candidate for 2,7
I4: 2,7 => CTR
* 892537164453618297671429385365...912924.51678187962453518..6.4.7.6...5212.91.58.6
I4: 1,8                                  # 12 pairs
I7: 2,7,3,9                              # reduction candidate for 2,7
I7: 2,7 => CTR
* 892537164453618.9.671429385365...9.1924.516.81879634525183962477.6...5.92.9..58.6
I7: 3,9                                  # 12 pairs
* PAIR F4: 2,4 COL F
F8: 2,4,3                                # reduction candidate for 2,4
F8: 2,4 => SOLVED
* 892537164453618297671429385365842971924751638187963452518296743736184529249375816
F8: 3 => CTR
* 892537164453618.9.671429385365..49..924.516..1879624535183.6.4.7.6...5..2.9..58.6
* PAIR F6: 2,3 COL F
F8: 2,3,4                                # reduction candidate for 2,3
F8: 4 => SOLVED
* 892537164453618297671429385365842971924751638187963452518296743736184529249375816
F8: 2,3                                  # 12 pairs
* PAIR H5: 3,7 BLK 6
I5: 3,7,8                                # reduction candidate for 3,7
I5: 3,7 => CTR
* 892537164453618.9.671429385365...9.89248516..187963452518..6.4.7.6.8.52.2.9..58.6
I5: 8                                    # 12 pairs
* PAIR H5: 3,7 ROW 5
D5: 3,7,8                                # reduction candidate for 3,7
D5: 8 => CTR
* 892537164453618.9.671429385365...9..9248516..187963452518..6.4.7.6.8.5292.9..5816
D5: 3,7                                  # 12 pairs
* PAIR H5: 3,7 COL H
H9: 3,7,1                                # reduction candidate for 3,7
H9: 1 => SOLVED
* 892537164453618297671429385365842971924751638187963452518296743736184529249375816
H9: 3,7                                  # 14 pairs
* PAIR I6: 2,3 COL I
I7: 2,3,7,9                              # reduction candidate for 2,3
I7: 2,3                                  # 13 pairs
I8: 2,3,1,9                              # reduction candidate for 2,3
I8: 2,3 => CTR
* 892537164453618.97671429385365.849.1924.516.818796.45.518376.497.6.9.5..2.9..58.6
I8: 1,9                                  # 12 pairs
* PAIR B8: 3,4 ROW 8
F8: 3,4,2                                # reduction candidate for 3,4
F8: 2 => CTR
* 892537164453618.9.671429385365..49..924.516..187963452518..6.4.7.6..25..2.9..58.6
F8: 3,4                                  # 15 pairs
* PAIR E7: 7,9 ROW 7
I7: 7,9,2,3                              # reduction candidate for 7,9
I7: 7,9 => CTR
* 892537164453618792671429385365...921924.516.818796.45.5183.624.7.6...5..2.9..58.6
I7: 2,3                                  # 13 pairs
* PAIR E9: 4,7 COL E
E4: 4,7,8                                # reduction candidate for 4,7
E4: 8                                    # 18 pairs
E4: 4,7                                  # 18 pairs
* PAIR G7: 2,7 BLK 9
I7: 2,7,3,9                              # reduction candidate for 2,7
I7: 2,7 => CTR
* 892537164453618.9.671429385365...9.1924.516.81879634525183962477.6...5.92.9..58.6
I7: 3,9                                  # 12 pairs
* PAIR G7: 2,7 ROW 7
D7: 2,7,3                                # reduction candidate for 2,7
D7: 2,7 => SOLVED
* 892537164453618297671429385365842971924751638187963452518296743736184529249375816
D7: 3 => CTR
* 892537164453618.9.671429385365...9..924.516..1879634525183.624.7.6...5..2.9..58.6
* INCONCLUSIVE
* SAVE PR GRAPH zz-www.sudokuoftheday.co.uk-20190128-absurd-base-pr-000.dot
* REASONING
* DIS # I4: 2,7 => CTR => I4: 1,8
* DIS # I7: 2,7 => CTR => I7: 3,9
* PRF # F8: 2,4 => SOL
* DIS # F8: 3 => CTR => F8: 2,4
* PRF # F8: 4 => SOL
* DIS # I5: 3,7 => CTR => I5: 8
* DIS # D5: 8 => CTR => D5: 3,7
* PRF # H9: 1 => SOL
* DIS # I8: 2,3 => CTR => I8: 1,9
* DIS # F8: 2 => CTR => F8: 3,4
* DIS # I7: 7,9 => CTR => I7: 2,3
* DIS # I7: 2,7 => CTR => I7: 3,9
* PRF # D7: 2,7 => SOL
* DIS # D7: 3 => CTR => D7: 2,7
* CNT  14 HDP CHAINS /  27 HYP OPENED

--------------------------------------------------
* PREPARE PR GRAPH
* PAIR REDUCTION ..
* LEVEL 0 PASS 1 ROUND 1 (AUTO SOLVE) (B8,B9,E7,E9,F4,F6,G2,G7,H5,I2,I6)
* 892537164453618.9.671429385365...9..924.516..18796.45.518..6.4.7.6...5..2.9..58.6
* PAIR I2: 2,7 COL I
I4: 2,7,1,8                              # reduction candidate for 2,7
I4: 2,7 => CTR
* 892537164453618297671429385365...912924.51678187962453518..6.4.7.6...5212.91.58.6
I7: 2,7,3,9                              # reduction candidate for 2,7
I7: 2,7 => CTR
* 892537164453618.9.671429385365...9.1924.516.81879634525183962477.6...5.92.9..58.6
* RESTART
* PAIR RESTART
* PAIR F4: 2,4 COL F
F8: 2,4,3                                # reduction candidate for 2,4
F8: 2,4 => SOLVED
* 892537164453618297671429385365842971924751638187963452518296743736184529249375816
* DURATION: 0:00:03.040811  START: 03:17:35.007339  END: 03:17:38.048150 2019-05-01
* SOLUTION FOUND
* SAVE PR GRAPH zz-www.sudokuoftheday.co.uk-20190128-absurd-base-pr-001.dot
* REASONING
* DIS # I4: 2,7 => CTR => I4: 1,8
* DIS I4: 1,8 # I7: 2,7 => CTR => I7: 3,9
* PRF I4: 1,8 + I7: 3,9 # F8: 2,4 => SOL
* STA I4: 1,8 + I7: 3,9 + F8: 2,4
* CNT   3 HDP CHAINS /   3 HYP OPENED

Header Info

http://www.sudokuoftheday.co.uk/cgi-bin/sudoku1280.cgi?ACTION=archive2&USER=&MONTH=Jan&YEAR=2019, 20190128, absurd

Solution

position: 892537164453618297671429385365842971924751638187963452518296743736184529249375816 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 # I4: 2,7 => CTR => I4: 1,8
* INC # I4: 1,8 => UNS
* DIS # I7: 2,7 => CTR => I7: 3,9
* INC # I7: 3,9 => UNS
* PRF # F8: 2,4 => SOL
* DIS # F8: 3 => CTR => F8: 2,4
* INC # F8: 2,3 => UNS
* PRF # F8: 4 => SOL
* DIS # I5: 3,7 => CTR => I5: 8
* INC # I5: 8 => UNS
* INC # D5: 3,7 => UNS
* DIS # D5: 8 => CTR => D5: 3,7
* INC # H9: 3,7 => UNS
* PRF # H9: 1 => SOL
* INC # I7: 2,3 => UNS
* DIS # I8: 2,3 => CTR => I8: 1,9
* INC # I8: 1,9 => UNS
* INC # F8: 3,4 => UNS
* DIS # F8: 2 => CTR => F8: 3,4
* DIS # I7: 7,9 => CTR => I7: 2,3
* INC # I7: 2,3 => UNS
* INC # E4: 4,7 => UNS
* INC # E4: 8 => UNS
* DIS # I7: 2,7 => CTR => I7: 3,9
* INC # I7: 3,9 => UNS
* PRF # D7: 2,7 => SOL
* DIS # D7: 3 => CTR => D7: 2,7
* CNT  27 HDP CHAINS /  27 HYP OPENED

A2. Pair Reduction

Full list of HDP chains traversed:

* DIS # I4: 2,7 => CTR => I4: 1,8
* DIS I4: 1,8 # I7: 2,7 => CTR => I7: 3,9
* PRF I4: 1,8 + I7: 3,9 # F8: 2,4 => SOL
* STA I4: 1,8 + I7: 3,9 + F8: 2,4
* CNT   3 HDP CHAINS /   3 HYP OPENED