Analysis of zz-www.sudokuoftheday.co.uk-20190120-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: .....9.2.9..47.....512.........1..8..7..94.3...8..597.6.....4.31...4389..3......2 initial

Autosolve

position: .....9.2.9.247.3...512...49....1..8..7.894.3..18..597.6.....4.312..4389..3......2 autosolve
Autosolve

Pair Reduction Variants

Pair Reduction Analysis

Pair Reduction Analysis

The following important HDP chains were detected:

* DIS # B1: 6,8 => CTR => B1: 4
* PRF # F2: 6,8 => SOL
* DIS # I2: 6,8 => CTR => I2: 1,5
* PRF # F2: 6,8 => SOL
* DIS # E3: 6,8 => CTR => E3: 3
* DIS # I1: 6,7 => CTR => I1: 1,8
* DIS # G5: 1,6 => CTR => G5: 2,5
* DIS # C4: 5,6 => CTR => C4: 3,4,9
* DIS # I5: 5,6 => CTR => I5: 1
* DIS # D4: 3,6 => CTR => D4: 7
* DIS # D1: 3,6 => CTR => D1: 1,5
* DIS # I4: 5 => CTR => I4: 4,6
* DIS # D8: 5,7 => CTR => D8: 6
* DIS # H9: 1,5 => CTR => H9: 6
* DIS # H2: 6 => CTR => H2: 1,5
* CNT  15 HDP CHAINS /  47 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 # B1: 6,8 => CTR => B1: 4
* PRF B1: 4 # F2: 6,8 => SOL
* STA B1: 4 + F2: 6,8
* CNT   2 HDP CHAINS /   2 HYP OPENED

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

Details

Positions

.....9.2.9..47.....512.........1..8..7..94.3...8..597.6.....4.31...4389..3......2 initial
.....9.2.9.247.3...512...49....1..8..7.894.3..18..597.6.....4.312..4389..3......2 autosolve
743159628962478315851236749394712586576894231218365974687921453125643897439587162 solved

Classification

level: medium

Pairing Analysis

--------------------------------------------------
* PAIRS (10)
B2: 6,8
F3: 6,8
G3: 6,7
A5: 2,5
C5: 5,6
D6: 3,6
I6: 4,6
B7: 8,9
C8: 5,7
H7: 1,5

--------------------------------------------------
* CONSTRAINT PAIRS (AUTO SOLVE)
D1,F2: 1.. / D1 = 1  =>  0 pairs (*) / F2 = 1  =>  0 pairs (X)
G5,I5: 1.. / G5 = 1  =>  0 pairs (X) / I5 = 1  => 10 pairs (_)
F4,E6: 2.. / F4 = 2  => 13 pairs (_) / E6 = 2  => 13 pairs (_)
G4,G5: 2.. / G4 = 2  => 12 pairs (_) / G5 = 2  => 10 pairs (_)
E7,F7: 2.. / E7 = 2  => 13 pairs (_) / F7 = 2  => 13 pairs (_)
A5,G5: 2.. / A5 = 2  => 12 pairs (_) / G5 = 2  => 10 pairs (_)
A6,E6: 2.. / A6 = 2  => 13 pairs (_) / E6 = 2  => 13 pairs (_)
E6,E7: 2.. / E6 = 2  => 13 pairs (_) / E7 = 2  => 13 pairs (_)
F4,F7: 2.. / F4 = 2  => 13 pairs (_) / F7 = 2  => 13 pairs (_)
A3,E3: 3.. / A3 = 3  =>  0 pairs (X) / E3 = 3  => 12 pairs (_)
C1,C4: 3.. / C1 = 3  => 13 pairs (_) / C4 = 3  => 16 pairs (_)
I4,I6: 4.. / I4 = 4  =>  0 pairs (X) / I6 = 4  => 13 pairs (_)
A9,C9: 4.. / A9 = 4  => 15 pairs (_) / C9 = 4  => 10 pairs (_)
A6,I6: 4.. / A6 = 4  =>  0 pairs (X) / I6 = 4  => 13 pairs (_)
B1,B4: 4.. / B1 = 4  => 11 pairs (_) / B4 = 4  =>  0 pairs (X)
D1,E1: 5.. / D1 = 5  => 15 pairs (_) / E1 = 5  => 12 pairs (_)
H2,I2: 5.. / H2 = 5  => 16 pairs (_) / I2 = 5  => 20 pairs (_)
D8,I8: 6.. / D8 = 6  => 15 pairs (_) / I8 = 6  =>  0 pairs (X)
H2,H9: 6.. / H2 = 6  =>  0 pairs (X) / H9 = 6  => 16 pairs (_)
D4,F4: 7.. / D4 = 7  => 13 pairs (_) / F4 = 7  =>  0 pairs (X)
I8,G9: 7.. / I8 = 7  => 15 pairs (_) / G9 = 7  =>  0 pairs (X)
A3,G3: 7.. / A3 = 7  => 19 pairs (_) / G3 = 7  => 17 pairs (_)
I1,I8: 7.. / I1 = 7  =>  0 pairs (X) / I8 = 7  => 15 pairs (_)
I1,I2: 8.. / I1 = 8  => 16 pairs (_) / I2 = 8  =>  0 pairs (X)
B7,A9: 8.. / B7 = 8  => 17 pairs (_) / A9 = 8  =>  0 pairs (X)
B4,C4: 9.. / B4 = 9  => 17 pairs (_) / C4 = 9  =>  0 pairs (X)
D7,D9: 9.. / D7 = 9  =>  0 pairs (*) / D9 = 9  =>  0 pairs (X)
C9,D9: 9.. / C9 = 9  =>  0 pairs (*) / D9 = 9  =>  0 pairs (X)
B4,B7: 9.. / B4 = 9  => 17 pairs (_) / B7 = 9  =>  0 pairs (X)
* DURATION: 0:00:27.216595  START: 03:05:21.787706  END: 03:05:49.004301 2019-05-01
* CP COUNT: (29)
* SOLUTION FOUND

--------------------------------------------------
* PREPARE PR GRAPH
* PAIR REDUCTION ..
* LEVEL 0 PASS 1 ROUND 1 (AUTO SOLVE) (A5,B2,B7,C5,C8,D6,F3,G3,H7,I6)
* .....9.2.9.247.3...512...49....1..8..7.894.3..18..597.6.....4.312..4389..3......2
* PAIR B2: 6,8 BLK 1
B1: 6,8,4                                # reduction candidate for 6,8
B1: 6,8 => CTR
* 4.3..9.2.9.247.3..751238649.49.1..86.76894.3..18..597469..824.312.64389.83495...2
B1: 4                                    # 11 pairs
* PAIR B2: 6,8 ROW 2
F2: 6,8,1                                # reduction candidate for 6,8
F2: 6,8 => SOLVED
* 743159628962478315851236749394712586576894231218365974687921453125643897439587162
F2: 1                                    # 13 pairs
I2: 6,8,1,5                              # reduction candidate for 6,8
I2: 6,8 => CTR
* .4.5.9.2.962471358.512...49.9471..8..76894.3.21836597468.927413127643895439158762
I2: 1,5                                  # 19 pairs
* PAIR F3: 6,8 BLK 2
E1: 6,8,3,5                              # reduction candidate for 6,8
E1: 6,8                                  # 17 pairs
F2: 6,8,1                                # reduction candidate for 6,8
F2: 6,8 => SOLVED
* 743159628962478315851236749394712586576894231218365974687921453125643897439587162
F2: 1                                    # 13 pairs
E3: 6,8,3                                # reduction candidate for 6,8
E3: 6,8 => CTR
* 847.39.2.9624713583512..749.93712.8..7689423..183.597.689..74.31256438977349...62
E3: 3                                    # 12 pairs
* PAIR F3: 6,8 COL F
F9: 6,8,1,7                              # reduction candidate for 6,8
F9: 6,8                                  # 16 pairs
F9: 1,7                                  # 11 pairs
* PAIR G3: 6,7 BLK 3
G1: 6,7,1                                # reduction candidate for 6,7
G1: 6,7                                  # 21 pairs
I1: 6,7,1,8                              # reduction candidate for 6,7
I1: 6,7 => CTR
* .4.5.912.962471358.512...49.9471..8..76894.3121836597468.9274131276438954391...62
I1: 1,8                                  # 16 pairs
* PAIR G3: 6,7 COL G
G9: 6,7,1,5                              # reduction candidate for 6,7
G9: 6,7                                  # 24 pairs
G9: 1,5                                  # 17 pairs
* PAIR A5: 2,5 BLK 4
A4: 2,5,3,4                              # reduction candidate for 2,5
A4: 2,5                                  # 15 pairs
A4: 3,4                                  # 11 pairs
* PAIR A5: 2,5 ROW 5
G5: 2,5,1,6                              # reduction candidate for 2,5
G5: 1,6 => CTR
* .....9.2.9.247.35..512...495...1628427689413541832597668..52413125643897734981562
G5: 2,5                                  # 11 pairs
* PAIR C5: 5,6 BLK 4
C4: 5,6,3,4,9                            # reduction candidate for 5,6
C4: 5,6 => CTR
* .43..9.2796247.3.8751238649.9..16.8.276894.31.18325976689.5.4.3127.4389.5349..762
C4: 3,4,9                                # 10 pairs
* PAIR C5: 5,6 ROW 5
G5: 5,6,1,2                              # reduction candidate for 5,6
G5: 5,6                                  # 13 pairs
I5: 5,6,1                                # reduction candidate for 5,6
I5: 5,6 => CTR
* .....9.2.9.247.35..512...495...1628427689413541832597668..52413125643897734981562
I5: 1                                    # 10 pairs
* PAIR D6: 3,6 BLK 5
D4: 3,6,7                                # reduction candidate for 3,6
D4: 3,6 => CTR
* .....9.279.247.36..512...49....17.8..7.894.3..18.2597.6....24.312..43896.3....7.2
D4: 7                                    # 13 pairs
E6: 3,6,2                                # reduction candidate for 3,6
E6: 3,6                                  # 13 pairs
* PAIR D6: 3,6 COL D
D1: 3,6,1,5                              # reduction candidate for 3,6
D1: 3,6 => CTR
* ....59.279.247136..512...49...71..8..7.894.3..18..597.6.....4.312.543896.3....7.2
D1: 1,5                                  # 12 pairs
* PAIR I6: 4,6 BLK 6
I4: 4,6,5                                # reduction candidate for 4,6
I4: 5 => CTR
* .....912.9.247135..512..749....1.685576894231.18..59746.....413125643897.3.187562
I4: 4,6                                  # 18 pairs
* PAIR C8: 5,7 BLK 7
C7: 5,7,9                                # reduction candidate for 5,7
C7: 5,7                                  # 15 pairs
A9: 5,7,4,8                              # reduction candidate for 5,7
A9: 5,7                                  # 16 pairs
C9: 5,7,4,9                              # reduction candidate for 5,7
C9: 5,7                                  # 14 pairs
* PAIR C8: 5,7 ROW 8
D8: 5,7,6                                # reduction candidate for 5,7
D8: 5,7 => CTR
* .....9.279.247.36..512...49....1..8..7.894.3..18..597.6.....4.312..43896.3....7.2
D8: 6                                    # 15 pairs
I8: 5,7,6                                # reduction candidate for 5,7
I8: 5,7                                  # 15 pairs
* PAIR H7: 1,5 BLK 9
G9: 1,5,6,7                              # reduction candidate for 1,5
G9: 1,5                                  # 17 pairs
H9: 1,5,6                                # reduction candidate for 1,5
H9: 1,5 => CTR
* .....91289824713653512..749..3.1..8..7.894.31.18..597.69....4.3125643897834957612
H9: 6                                    # 16 pairs
* PAIR H7: 1,5 ROW 7
D7: 1,5,7,9                              # reduction candidate for 1,5
D7: 1,5                                  # 13 pairs
D7: 7,9                                  # 11 pairs
* PAIR H7: 1,5 COL H
H2: 1,5,6                                # reduction candidate for 1,5
H2: 6 => CTR
* .....91289824713653512..749..3.1..8..7.894.31.18..597.69....4.3125643897834957612
H2: 1,5                                  # 16 pairs
* INCONCLUSIVE
* SAVE PR GRAPH zz-www.sudokuoftheday.co.uk-20190120-absurd-base-pr-000.dot
* REASONING
* DIS # B1: 6,8 => CTR => B1: 4
* PRF # F2: 6,8 => SOL
* DIS # I2: 6,8 => CTR => I2: 1,5
* PRF # F2: 6,8 => SOL
* DIS # E3: 6,8 => CTR => E3: 3
* DIS # I1: 6,7 => CTR => I1: 1,8
* DIS # G5: 1,6 => CTR => G5: 2,5
* DIS # C4: 5,6 => CTR => C4: 3,4,9
* DIS # I5: 5,6 => CTR => I5: 1
* DIS # D4: 3,6 => CTR => D4: 7
* DIS # D1: 3,6 => CTR => D1: 1,5
* DIS # I4: 5 => CTR => I4: 4,6
* DIS # D8: 5,7 => CTR => D8: 6
* DIS # H9: 1,5 => CTR => H9: 6
* DIS # H2: 6 => CTR => H2: 1,5
* CNT  15 HDP CHAINS /  47 HYP OPENED

--------------------------------------------------
* PREPARE PR GRAPH
* PAIR REDUCTION ..
* LEVEL 0 PASS 1 ROUND 1 (AUTO SOLVE) (A5,B2,B7,C5,C8,D6,F3,G3,H7,I6)
* .....9.2.9.247.3...512...49....1..8..7.894.3..18..597.6.....4.312..4389..3......2
* PAIR B2: 6,8 BLK 1
B1: 6,8,4                                # reduction candidate for 6,8
B1: 6,8 => CTR
* 4.3..9.2.9.247.3..751238649.49.1..86.76894.3..18..597469..824.312.64389.83495...2
* PAIR B2: 6,8 ROW 2
F2: 6,8,1                                # reduction candidate for 6,8
F2: 6,8 => SOLVED
* 743159628962478315851236749394712586576894231218365974687921453125643897439587162
* DURATION: 0:00:02.855775  START: 03:06:14.426729  END: 03:06:17.282504 2019-05-01
* SOLUTION FOUND
* SAVE PR GRAPH zz-www.sudokuoftheday.co.uk-20190120-absurd-base-pr-001.dot
* REASONING
* DIS # B1: 6,8 => CTR => B1: 4
* PRF B1: 4 # F2: 6,8 => SOL
* STA B1: 4 + F2: 6,8
* CNT   2 HDP CHAINS /   2 HYP OPENED

Header Info

http://www.sudokuoftheday.co.uk/cgi-bin/sudoku1280.cgi?ACTION=archive2&USER=&MONTH=Jan&YEAR=2019, 20190120, absurd

Solution

position: 743159628962478315851236749394712586576894231218365974687921453125643897439587162 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 # B1: 6,8 => CTR => B1: 4
* INC # B1: 4 => UNS
* PRF # F2: 6,8 => SOL
* INC # F2: 1 => UNS
* DIS # I2: 6,8 => CTR => I2: 1,5
* INC # I2: 1,5 => UNS
* INC # E1: 6,8 => UNS
* PRF # F2: 6,8 => SOL
* INC # F2: 1 => UNS
* DIS # E3: 6,8 => CTR => E3: 3
* INC # E3: 3 => UNS
* INC # F9: 6,8 => UNS
* INC # F9: 1,7 => UNS
* INC # G1: 6,7 => UNS
* DIS # I1: 6,7 => CTR => I1: 1,8
* INC # I1: 1,8 => UNS
* INC # G9: 6,7 => UNS
* INC # G9: 1,5 => UNS
* INC # A4: 2,5 => UNS
* INC # A4: 3,4 => UNS
* INC # G5: 2,5 => UNS
* DIS # G5: 1,6 => CTR => G5: 2,5
* DIS # C4: 5,6 => CTR => C4: 3,4,9
* INC # C4: 3,4,9 => UNS
* INC # G5: 5,6 => UNS
* DIS # I5: 5,6 => CTR => I5: 1
* INC # I5: 1 => UNS
* DIS # D4: 3,6 => CTR => D4: 7
* INC # D4: 7 => UNS
* INC # E6: 3,6 => UNS
* DIS # D1: 3,6 => CTR => D1: 1,5
* INC # D1: 1,5 => UNS
* INC # I4: 4,6 => UNS
* DIS # I4: 5 => CTR => I4: 4,6
* INC # C7: 5,7 => UNS
* INC # A9: 5,7 => UNS
* INC # C9: 5,7 => UNS
* DIS # D8: 5,7 => CTR => D8: 6
* INC # D8: 6 => UNS
* INC # I8: 5,7 => UNS
* INC # G9: 1,5 => UNS
* DIS # H9: 1,5 => CTR => H9: 6
* INC # H9: 6 => UNS
* INC # D7: 1,5 => UNS
* INC # D7: 7,9 => UNS
* INC # H2: 1,5 => UNS
* DIS # H2: 6 => CTR => H2: 1,5
* CNT  47 HDP CHAINS /  47 HYP OPENED

A2. Pair Reduction

Full list of HDP chains traversed:

* DIS # B1: 6,8 => CTR => B1: 4
* PRF B1: 4 # F2: 6,8 => SOL
* STA B1: 4 + F2: 6,8
* CNT   2 HDP CHAINS /   2 HYP OPENED