Analysis of zz-www.sudokuoftheday.co.uk-20190324-absurd-base.sdk

Contents

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

level: medium

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

position: ..7...6.1.....3......8..4.9.4...182.29..4......3.....6....29...65......8...75.... initial

Autosolve

position: ..7.9.6.1.....3......8..4.9.469.182.298.46.....3.8.946...629...652..4798...758.6. autosolve
Autosolve

Pair Reduction Variants

Pair Reduction Analysis

Pair Reduction Analysis

The following important HDP chains were detected:

* DIS # B3: 1,3 => CTR => B3: 2,6
* DIS # A9: 1,3 => CTR => A9: 4,9
* DIS # C2: 1,5 => CTR => C2: 4,9
* DIS # I2: 7 => CTR => I2: 2,5
* DIS # A6: 1 => CTR => A6: 5,7
* DIS # I5: 3,5 => CTR => I5: 7
* DIS # I5: 3,5 => CTR => I5: 7
* DIS # I7: 4 => CTR => I7: 3,5
* DIS # A9: 1,3 => CTR => A9: 4,9
* DIS # B3: 1,3 => CTR => B3: 2,6
* PRF # G7: 1,5 => SOL
* DIS # H5: 7 => CTR => H5: 1,5
* CNT  12 HDP CHAINS /  40 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 # B3: 1,3 => CTR => B3: 2,6
* DIS B3: 2,6 # A9: 1,3 => CTR => A9: 4,9
* DIS B3: 2,6 + A9: 4,9 # D1: 2,5 => CTR => D1: 4
* PRF B3: 2,6 + A9: 4,9 + D1: 4 # I2: 2,5 => SOL
* STA B3: 2,6 + A9: 4,9 + D1: 4 + I2: 2,5
* CNT   4 HDP CHAINS /   4 HYP OPENED

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

Details

Positions

..7...6.1.....3......8..4.9.4...182.29..4......3.....6....29...65......8...75.... initial
..7.9.6.1.....3......8..4.9.469.182.298.46.....3.8.946...629...652..4798...758.6. autosolve
327495681489163572165872439746931825298546317513287946874629153652314798931758264 solved

Classification

level: medium

Pairing Analysis

--------------------------------------------------
* PAIRS (19)
A3: 1,3
C3: 1,5
F1: 2,5
G2: 2,5
A4: 5,7
B6: 1,7
E4: 3,7
D5: 3,5
D6: 2,5
I4: 3,5
A7: 7,8
B7: 7,8
C7: 1,4
B9: 1,3
D8: 1,3
E8: 1,3
H7: 1,5
G9: 1,2
I9: 2,4

--------------------------------------------------
* CONSTRAINT PAIRS (AUTO SOLVE)
A6,B6: 1.. / A6 = 1  =>  0 pairs (X) / B6 = 1  => 20 pairs (_)
G5,H5: 1.. / G5 = 1  =>  0 pairs (X) / H5 = 1  => 26 pairs (_)
D8,E8: 1.. / D8 = 1  => 21 pairs (_) / E8 = 1  => 14 pairs (_)
D2,D8: 1.. / D2 = 1  => 14 pairs (_) / D8 = 1  => 21 pairs (_)
H5,H7: 1.. / H5 = 1  => 26 pairs (_) / H7 = 1  =>  0 pairs (X)
B1,B3: 2.. / B1 = 2  => 14 pairs (_) / B3 = 2  => 22 pairs (_)
G2,I2: 2.. / G2 = 2  =>  0 pairs (X) / I2 = 2  => 25 pairs (_)
D6,F6: 2.. / D6 = 2  => 20 pairs (_) / F6 = 2  => 20 pairs (_)
G9,I9: 2.. / G9 = 2  => 25 pairs (_) / I9 = 2  =>  0 pairs (X)
B3,F3: 2.. / B3 = 2  => 22 pairs (_) / F3 = 2  => 14 pairs (_)
D1,D6: 2.. / D1 = 2  => 20 pairs (_) / D6 = 2  => 20 pairs (_)
G2,G9: 2.. / G2 = 2  =>  0 pairs (X) / G9 = 2  => 25 pairs (_)
I2,I9: 2.. / I2 = 2  => 25 pairs (_) / I9 = 2  =>  0 pairs (X)
H1,H3: 3.. / H1 = 3  => 25 pairs (_) / H3 = 3  => 25 pairs (_)
E4,D5: 3.. / E4 = 3  => 14 pairs (_) / D5 = 3  => 21 pairs (_)
A9,B9: 3.. / A9 = 3  =>  0 pairs (X) / B9 = 3  => 19 pairs (_)
D8,E8: 3.. / D8 = 3  => 14 pairs (_) / E8 = 3  => 21 pairs (_)
G7,I7: 3.. / G7 = 3  => 21 pairs (_) / I7 = 3  =>  0 pairs (*)
E4,I4: 3.. / E4 = 3  => 14 pairs (_) / I4 = 3  => 21 pairs (_)
D5,D8: 3.. / D5 = 3  => 21 pairs (_) / D8 = 3  => 14 pairs (_)
E4,E8: 3.. / E4 = 3  => 14 pairs (_) / E8 = 3  => 21 pairs (_)
G5,G7: 3.. / G5 = 3  =>  0 pairs (*) / G7 = 3  =>  0 pairs (X)
D1,D2: 4.. / D1 = 4  => 25 pairs (_) / D2 = 4  => 24 pairs (_)
I7,I9: 4.. / I7 = 4  =>  0 pairs (X) / I9 = 4  => 25 pairs (_)
A1,D1: 4.. / A1 = 4  => 24 pairs (_) / D1 = 4  => 25 pairs (_)
C7,I7: 4.. / C7 = 4  => 25 pairs (_) / I7 = 4  =>  0 pairs (X)
C2,C3: 5.. / C2 = 5  =>  0 pairs (X) / C3 = 5  => 20 pairs (_)
A4,A6: 5.. / A4 = 5  => 21 pairs (_) / A6 = 5  => 14 pairs (_)
A4,I4: 5.. / A4 = 5  => 21 pairs (_) / I4 = 5  => 14 pairs (_)
B2,B3: 6.. / B2 = 6  => 20 pairs (_) / B3 = 6  => 14 pairs (_)
E2,E3: 6.. / E2 = 6  => 14 pairs (_) / E3 = 6  => 20 pairs (_)
B2,E2: 6.. / B2 = 6  => 20 pairs (_) / E2 = 6  => 14 pairs (_)
B3,E3: 6.. / B3 = 6  => 14 pairs (_) / E3 = 6  => 20 pairs (_)
E4,F6: 7.. / E4 = 7  => 21 pairs (_) / F6 = 7  => 14 pairs (_)
H5,I5: 7.. / H5 = 7  =>  0 pairs (X) / I5 = 7  => 25 pairs (_)
A7,B7: 7.. / A7 = 7  =>  0 pairs (X) / B7 = 7  => 20 pairs (_)
A4,E4: 7.. / A4 = 7  => 14 pairs (_) / E4 = 7  => 21 pairs (_)
B6,B7: 7.. / B6 = 7  =>  0 pairs (X) / B7 = 7  => 20 pairs (_)
F3,F6: 7.. / F3 = 7  => 21 pairs (_) / F6 = 7  => 14 pairs (_)
I2,I5: 7.. / I2 = 7  =>  0 pairs (X) / I5 = 7  => 25 pairs (_)
H1,H2: 8.. / H1 = 8  => 14 pairs (_) / H2 = 8  => 21 pairs (_)
A7,B7: 8.. / A7 = 8  => 20 pairs (_) / B7 = 8  =>  0 pairs (X)
A2,C2: 9.. / A2 = 9  => 19 pairs (_) / C2 = 9  => 21 pairs (_)
A9,C9: 9.. / A9 = 9  => 21 pairs (_) / C9 = 9  => 19 pairs (_)
A2,A9: 9.. / A2 = 9  => 19 pairs (_) / A9 = 9  => 21 pairs (_)
C2,C9: 9.. / C2 = 9  => 21 pairs (_) / C9 = 9  => 19 pairs (_)
* DURATION: 0:00:58.613330  START: 04:46:03.253643  END: 04:47:01.866973 2019-05-01
* CP COUNT: (46)
* SOLUTION FOUND

--------------------------------------------------
* PREPARE PR GRAPH
* PAIR REDUCTION ..
* LEVEL 0 PASS 1 ROUND 1 (AUTO SOLVE) (A3,A4,A7,B6,B7,B9,C3,C7,D5,D6,D8,E4,E8,F1,G2,G9,H7,I4,I9)
* ..7.9.6.1.....3......8..4.9.469.182.298.46.....3.8.946...629...652..4798...758.6.
* PAIR A3: 1,3 BLK 1
B3: 1,3,2,6                              # reduction candidate for 1,3
B3: 1,3 => CTR
* .27.956.1.6...3......862479.469.182.298.46..7..3287946...629...652..4798...758.6.
B3: 2,6                                  # 20 pairs
* PAIR A3: 1,3 COL A
A9: 1,3,4,9                              # reduction candidate for 1,3
A9: 1,3 => CTR
* 4.7.9.6319.14.35.2..58..4.9.46971823298346157713.8.946874629315652134798139758264
A9: 4,9                                  # 22 pairs
* PAIR C3: 1,5 BLK 1
C2: 1,5,4,9                              # reduction candidate for 1,5
C2: 1,5 => CTR
* 4.7.9.6.19..4.35.2..58.7439546971823298346157713.8.946874629315652134798..9758264
C2: 4,9                                  # 22 pairs
* PAIR F1: 2,5 BLK 2
D1: 2,5,4                                # reduction candidate for 2,5
D1: 2,5                                  # 24 pairs
F3: 2,5,7                                # reduction candidate for 2,5
F3: 2,5                                  # 14 pairs
* PAIR F1: 2,5 COL F
F6: 2,5,7                                # reduction candidate for 2,5
F6: 2,5                                  # 21 pairs
F6: 7                                    # 14 pairs
* PAIR G2: 2,5 BLK 3
I2: 2,5,7                                # reduction candidate for 2,5
I2: 7 => CTR
* ..7.9.6.1.....32.7...8..4.9.469.182.298.46.7...3.8.946...629.1.652..4798...758.6.
I2: 2,5                                  # 25 pairs
* PAIR A4: 5,7 BLK 4
A6: 5,7,1                                # reduction candidate for 5,7
A6: 1 => CTR
* ..7.9.6.1.....3...3..8.745954697182329834651.173.8.94678.6293..652134798...758.6.
A6: 5,7                                  # 20 pairs
* PAIR B6: 1,7 BLK 4
A6: 1,7,5                                # reduction candidate for 1,7
A6: 1,7                                  # 21 pairs
A6: 5                                    # 14 pairs
* PAIR D5: 3,5 ROW 5
G5: 3,5,1                                # reduction candidate for 3,5
G5: 3,5                                  # 26 pairs
I5: 3,5,7                                # reduction candidate for 3,5
I5: 3,5 => CTR
* ..7.9.6.1.....3..7...8..4.9.469.182.298.46.7...3.8.946...629.1.652..4798...758264
I5: 7                                    # 25 pairs
* PAIR D6: 2,5 BLK 5
F6: 2,5,7                                # reduction candidate for 2,5
F6: 2,5                                  # 21 pairs
F6: 7                                    # 14 pairs
* PAIR D6: 2,5 COL D
D1: 2,5,4                                # reduction candidate for 2,5
D1: 4                                    # 25 pairs
D1: 2,5                                  # 24 pairs
* PAIR I4: 3,5 BLK 6
G5: 3,5,1                                # reduction candidate for 3,5
G5: 3,5                                  # 26 pairs
I5: 3,5,7                                # reduction candidate for 3,5
I5: 3,5 => CTR
* ..7.9.6.1.....3..7...8..4.9.469.182.298.46.7...3.8.946...629.1.652..4798...758264
I5: 7                                    # 25 pairs
* PAIR I4: 3,5 COL I
I7: 3,5,4                                # reduction candidate for 3,5
I7: 4 => CTR
* ..7.9.6.1...4.3275..58.7439546971823298346517..3.8.946..1629354652134798.34758162
I7: 3,5                                  # 25 pairs
* PAIR C7: 1,4 BLK 7
A9: 1,4,3,9                              # reduction candidate for 1,4
A9: 1,4                                  # 20 pairs
C9: 1,4,9                                # reduction candidate for 1,4
C9: 1,4                                  # 21 pairs
* PAIR C7: 1,4 COL C
C2: 1,4,5,9                              # reduction candidate for 1,4
C2: 1,4                                  # 21 pairs
C2: 5,9                                  # 20 pairs
* PAIR B9: 1,3 BLK 7
A9: 1,3,4,9                              # reduction candidate for 1,3
A9: 1,3 => CTR
* 4.7.9.6319.14.35.2..58..4.9.46971823298346157713.8.946874629315652134798139758264
A9: 4,9                                  # 22 pairs
* PAIR B9: 1,3 COL B
B3: 1,3,2,6                              # reduction candidate for 1,3
B3: 1,3 => CTR
* .27.956.1.6...3......862479.469.182.298.46..7..3287946...629...652..4798...758.6.
B3: 2,6                                  # 20 pairs
* PAIR H7: 1,5 BLK 9
G7: 1,5,3                                # reduction candidate for 1,5
G7: 1,5 => SOLVED
* 327495681489163572165872439746931825298546317513287946874629153652314798931758264
G7: 3                                    # 21 pairs
* PAIR H7: 1,5 COL H
H5: 1,5,7                                # reduction candidate for 1,5
H5: 7 => CTR
* ..7.9.6.1.....3......8..4.9.469.182.298.4617...3.8.946...629315652..4798...758264
H5: 1,5                                  # 25 pairs
* INCONCLUSIVE
* SAVE PR GRAPH zz-www.sudokuoftheday.co.uk-20190324-absurd-base-pr-000.dot
* REASONING
* DIS # B3: 1,3 => CTR => B3: 2,6
* DIS # A9: 1,3 => CTR => A9: 4,9
* DIS # C2: 1,5 => CTR => C2: 4,9
* DIS # I2: 7 => CTR => I2: 2,5
* DIS # A6: 1 => CTR => A6: 5,7
* DIS # I5: 3,5 => CTR => I5: 7
* DIS # I5: 3,5 => CTR => I5: 7
* DIS # I7: 4 => CTR => I7: 3,5
* DIS # A9: 1,3 => CTR => A9: 4,9
* DIS # B3: 1,3 => CTR => B3: 2,6
* PRF # G7: 1,5 => SOL
* DIS # H5: 7 => CTR => H5: 1,5
* CNT  12 HDP CHAINS /  40 HYP OPENED

--------------------------------------------------
* PREPARE PR GRAPH
* PAIR REDUCTION ..
* LEVEL 0 PASS 1 ROUND 1 (AUTO SOLVE) (A3,A4,A7,B6,B7,B9,C3,C7,D5,D6,D8,E4,E8,F1,G2,G9,H7,I4,I9)
* ..7.9.6.1.....3......8..4.9.469.182.298.46.....3.8.946...629...652..4798...758.6.
* PAIR A3: 1,3 BLK 1
B3: 1,3,2,6                              # reduction candidate for 1,3
B3: 1,3 => CTR
* .27.956.1.6...3......862479.469.182.298.46..7..3287946...629...652..4798...758.6.
* PAIR A3: 1,3 COL A
A9: 1,3,4,9                              # reduction candidate for 1,3
A9: 1,3 => CTR
* 4.7.9.6319.14.35.2..58..4.9.46971823298346157713.8.946874629315652134798139758264
* PAIR RESTART
* PAIR F1: 2,5 BLK 2
D1: 2,5,4                                # reduction candidate for 2,5
D1: 2,5 => CTR
* 4.7.9.631..94.3.8.3.581.479.469.182.298.46..7..3.8794687.629...652134798.3.758.6.
* PAIR G2: 2,5 BLK 3
I2: 2,5,7                                # reduction candidate for 2,5
I2: 2,5 => SOLVED
* 327495681489163572165872439746931825298546317513287946874629153652314798931758264
* DURATION: 0:00:06.068306  START: 04:47:28.312941  END: 04:47:34.381247 2019-05-01
* SOLUTION FOUND
* SAVE PR GRAPH zz-www.sudokuoftheday.co.uk-20190324-absurd-base-pr-001.dot
* REASONING
* DIS # B3: 1,3 => CTR => B3: 2,6
* DIS B3: 2,6 # A9: 1,3 => CTR => A9: 4,9
* DIS B3: 2,6 + A9: 4,9 # D1: 2,5 => CTR => D1: 4
* PRF B3: 2,6 + A9: 4,9 + D1: 4 # I2: 2,5 => SOL
* STA B3: 2,6 + A9: 4,9 + D1: 4 + I2: 2,5
* CNT   4 HDP CHAINS /   4 HYP OPENED

Header Info

http://www.sudokuoftheday.co.uk/cgi-bin/sudoku1280.cgi?ACTION=archive2&USER=&MONTH=Mar&YEAR=2019, 20190324, absurd

Solution

position: 327495681489163572165872439746931825298546317513287946874629153652314798931758264 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 # B3: 1,3 => CTR => B3: 2,6
* INC # B3: 2,6 => UNS
* DIS # A9: 1,3 => CTR => A9: 4,9
* INC # A9: 4,9 => UNS
* DIS # C2: 1,5 => CTR => C2: 4,9
* INC # C2: 4,9 => UNS
* INC # D1: 2,5 => UNS
* INC # F3: 2,5 => UNS
* INC # F6: 2,5 => UNS
* INC # F6: 7 => UNS
* INC # I2: 2,5 => UNS
* DIS # I2: 7 => CTR => I2: 2,5
* INC # A6: 5,7 => UNS
* DIS # A6: 1 => CTR => A6: 5,7
* INC # A6: 1,7 => UNS
* INC # A6: 5 => UNS
* INC # G5: 3,5 => UNS
* DIS # I5: 3,5 => CTR => I5: 7
* INC # I5: 7 => UNS
* INC # F6: 2,5 => UNS
* INC # F6: 7 => UNS
* INC # D1: 2,5 => UNS
* INC # D1: 4 => UNS
* INC # G5: 3,5 => UNS
* DIS # I5: 3,5 => CTR => I5: 7
* INC # I5: 7 => UNS
* INC # I7: 3,5 => UNS
* DIS # I7: 4 => CTR => I7: 3,5
* INC # A9: 1,4 => UNS
* INC # C9: 1,4 => UNS
* INC # C2: 1,4 => UNS
* INC # C2: 5,9 => UNS
* DIS # A9: 1,3 => CTR => A9: 4,9
* INC # A9: 4,9 => UNS
* DIS # B3: 1,3 => CTR => B3: 2,6
* INC # B3: 2,6 => UNS
* PRF # G7: 1,5 => SOL
* INC # G7: 3 => UNS
* INC # H5: 1,5 => UNS
* DIS # H5: 7 => CTR => H5: 1,5
* CNT  40 HDP CHAINS /  40 HYP OPENED

A2. Pair Reduction

Full list of HDP chains traversed:

* DIS # B3: 1,3 => CTR => B3: 2,6
* DIS B3: 2,6 # A9: 1,3 => CTR => A9: 4,9
* DIS B3: 2,6 + A9: 4,9 # D1: 2,5 => CTR => D1: 4
* PRF B3: 2,6 + A9: 4,9 + D1: 4 # I2: 2,5 => SOL
* STA B3: 2,6 + A9: 4,9 + D1: 4 + I2: 2,5
* CNT   4 HDP CHAINS /   4 HYP OPENED