Analysis of zz-www.sudokuoftheday.co.uk-20190403-absurd-base.sdk

Contents

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

level: medium

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

position: ...14.8.52.....9.1..1.25.4...8...16.4....2..8.39.7....57..8.........6..29..5..... initial

Autosolve

position: ..714.8252.....9.1..1.25.4.728.5.16.4....2..8.39.7.25457.28.........65.29.25..... autosolve
Autosolve

Pair Reduction Variants

Pair Reduction Analysis

Pair Reduction Analysis

The following important HDP chains were detected:

* DIS # D3: 7 => CTR => D3: 3,9
* PRF # F7: 3,9 => SOL
* DIS # D2: 3,6 => CTR => D2: 7,8
* PRF # E5: 3,6 => SOL
* DIS # G3: 3,7 => CTR => G3: 6
* PRF # D2: 3,7 => SOL
* DIS # F2: 3,7 => CTR => F2: 8
* PRF # F2: 8 => SOL
* DIS # H5: 3,7 => CTR => H5: 9
* DIS # H9: 3,7 => CTR => H9: 1,8
* DIS # B5: 5,6 => CTR => B5: 1
* PRF # B5: 1 => SOL
* DIS # B5: 5 => CTR => B5: 1,6
* PRF # D2: 3,7 => SOL
* DIS # H5: 7 => CTR => H5: 3,9
* PRF # D4: 3,9 => SOL
* DIS # I7: 6 => CTR => I7: 3,9
* DIS # H5: 3,7 => CTR => H5: 9
* DIS # G3: 3,7 => CTR => G3: 6
* DIS # H8: 1,8 => CTR => H8: 3,7,9
* DIS # C7: 3,4 => CTR => C7: 6
* PRF # D8: 3,4 => SOL
* DIS # E8: 1,3 => CTR => E8: 9
* DIS # F9: 1,3 => CTR => F9: 4,7
* DIS # H9: 1,3 => CTR => H9: 7,8
* DIS # E5: 6,9 => CTR => E5: 1,3
* CNT  26 HDP CHAINS /  56 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 # D3: 7 => CTR => D3: 3,9
* PRF D3: 3,9 # F7: 3,9 => SOL
* STA D3: 3,9 + F7: 3,9
* CNT   2 HDP CHAINS /   4 HYP OPENED

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

Details

Positions

...14.8.52.....9.1..1.25.4...8...16.4....2..8.39.7....57..8.........6..29..5..... initial
..714.8252.....9.1..1.25.4.728.5.16.4....2..8.39.7.25457.28.........65.29.25..... autosolve
367149825254768931891325647728954163415632798639871254576283419183496572942517386 solved

Classification

level: medium

Pairing Analysis

--------------------------------------------------
* PAIRS (18)
A1: 3,6
B1: 6,9
B2: 4,5
C2: 4,5
A3: 3,8
B3: 8,9
F1: 3,9
E2: 3,6
H2: 3,7
C5: 5,6
A6: 1,6
D6: 6,8
F6: 1,8
I4: 3,9
G5: 3,7
A8: 1,8
C8: 3,4
E9: 1,3

--------------------------------------------------
* CONSTRAINT PAIRS (AUTO SOLVE)
B5,A6: 1.. / B5 = 1  =>  0 pairs (*) / A6 = 1  =>  0 pairs (X)
E5,F6: 1.. / E5 = 1  =>  0 pairs (X) / F6 = 1  =>  0 pairs (_)
B5,E5: 1.. / B5 = 1  =>  0 pairs (*) / E5 = 1  =>  0 pairs (X)
A6,F6: 1.. / A6 = 1  =>  0 pairs (X) / F6 = 1  =>  0 pairs (_)
F7,H7: 1.. / F7 = 1  =>  0 pairs (X) / H7 = 1  => 20 pairs (_)
A6,A8: 1.. / A6 = 1  =>  0 pairs (X) / A8 = 1  =>  0 pairs (_)
A1,A3: 3.. / A1 = 3  =>  0 pairs (*) / A3 = 3  =>  0 pairs (X)
C7,C8: 3.. / C7 = 3  =>  0 pairs (X) / C8 = 3  => 19 pairs (_)
A1,F1: 3.. / A1 = 3  =>  0 pairs (*) / F1 = 3  =>  0 pairs (X)
B2,C2: 4.. / B2 = 4  =>  0 pairs (X) / C2 = 4  => 20 pairs (_)
D4,F4: 4.. / D4 = 4  => 22 pairs (_) / F4 = 4  =>  0 pairs (*)
G7,G9: 4.. / G7 = 4  => 21 pairs (_) / G9 = 4  => 19 pairs (_)
D4,D8: 4.. / D4 = 4  => 22 pairs (_) / D8 = 4  =>  0 pairs (*)
B2,C2: 5.. / B2 = 5  => 20 pairs (_) / C2 = 5  =>  0 pairs (X)
B5,C5: 5.. / B5 = 5  =>  0 pairs (X) / C5 = 5  => 20 pairs (_)
B2,B5: 5.. / B2 = 5  => 20 pairs (_) / B5 = 5  =>  0 pairs (X)
C2,C5: 5.. / C2 = 5  =>  0 pairs (X) / C5 = 5  => 20 pairs (_)
A1,B1: 6.. / A1 = 6  =>  0 pairs (X) / B1 = 6  =>  0 pairs (_)
D2,E2: 6.. / D2 = 6  =>  0 pairs (X) / E2 = 6  => 17 pairs (_)
G3,I3: 6.. / G3 = 6  => 20 pairs (_) / I3 = 6  =>  0 pairs (X)
C7,B9: 6.. / C7 = 6  => 20 pairs (_) / B9 = 6  =>  0 pairs (X)
A6,D6: 6.. / A6 = 6  =>  0 pairs (*) / D6 = 6  =>  0 pairs (X)
A1,A6: 6.. / A1 = 6  =>  0 pairs (X) / A6 = 6  =>  0 pairs (_)
C5,C7: 6.. / C5 = 6  =>  0 pairs (X) / C7 = 6  => 20 pairs (_)
E2,E5: 6.. / E2 = 6  => 17 pairs (_) / E5 = 6  =>  0 pairs (X)
G5,H5: 7.. / G5 = 7  => 19 pairs (_) / H5 = 7  =>  0 pairs (X)
D8,F9: 7.. / D8 = 7  =>  0 pairs (X) / F9 = 7  =>  0 pairs (_)
D8,H8: 7.. / D8 = 7  =>  0 pairs (X) / H8 = 7  =>  0 pairs (_)
F2,F9: 7.. / F2 = 7  =>  0 pairs (X) / F9 = 7  =>  0 pairs (_)
I3,I9: 7.. / I3 = 7  => 23 pairs (_) / I9 = 7  =>  0 pairs (X)
A3,B3: 8.. / A3 = 8  =>  0 pairs (*) / B3 = 8  =>  0 pairs (X)
D2,F2: 8.. / D2 = 8  =>  0 pairs (X) / F2 = 8  =>  0 pairs (_)
D6,F6: 8.. / D6 = 8  =>  0 pairs (*) / F6 = 8  =>  0 pairs (X)
H8,H9: 8.. / H8 = 8  =>  0 pairs (X) / H9 = 8  => 18 pairs (_)
B9,H9: 8.. / B9 = 8  =>  0 pairs (X) / H9 = 8  => 18 pairs (_)
A3,A8: 8.. / A3 = 8  =>  0 pairs (*) / A8 = 8  =>  0 pairs (X)
D2,D6: 8.. / D2 = 8  =>  0 pairs (X) / D6 = 8  =>  0 pairs (_)
F2,F6: 8.. / F2 = 8  =>  0 pairs (*) / F6 = 8  =>  0 pairs (X)
B1,B3: 9.. / B1 = 9  =>  0 pairs (X) / B3 = 9  =>  0 pairs (_)
F1,D3: 9.. / F1 = 9  =>  0 pairs (*) / D3 = 9  =>  0 pairs (X)
I4,H5: 9.. / I4 = 9  =>  0 pairs (X) / H5 = 9  => 23 pairs (_)
B1,F1: 9.. / B1 = 9  =>  0 pairs (X) / F1 = 9  =>  0 pairs (_)
B3,D3: 9.. / B3 = 9  =>  0 pairs (*) / D3 = 9  =>  0 pairs (X)
E5,E8: 9.. / E5 = 9  =>  0 pairs (X) / E8 = 9  => 18 pairs (_)
I4,I7: 9.. / I4 = 9  =>  0 pairs (X) / I7 = 9  => 23 pairs (_)
* DURATION: 0:00:55.189863  START: 05:01:59.199227  END: 05:02:54.389090 2019-05-01
* CP COUNT: (45)
* SOLUTION FOUND

--------------------------------------------------
* PREPARE PR GRAPH
* PAIR REDUCTION ..
* LEVEL 0 PASS 1 ROUND 1 (AUTO SOLVE) (A1,A3,A6,A8,B1,B2,B3,C2,C5,C8,D6,E2,E9,F1,F6,G5,H2,I4)
* ..714.8252.....9.1..1.25.4.728.5.16.4....2..8.39.7.25457.28.........65.29.25.....
* PAIR F1: 3,9 BLK 2
D3: 3,9,7                                # reduction candidate for 3,9
D3: 7 => CTR
* ..71498252.....9.1.91725.4.728.5.16.4....2..8.39.7.25457.28.........65729.25.7.8.
D3: 3,9                                  # 23 pairs
* PAIR F1: 3,9 COL F
F4: 3,9,4                                # reduction candidate for 3,9
F4: 3,9                                  # 22 pairs
F7: 3,9,1,4                              # reduction candidate for 3,9
F7: 3,9 => SOLVED
* 367149825254768931891325647728954163415632798639871254576283419183496572942517386
F7: 1,4                                  # 19 pairs
* PAIR E2: 3,6 BLK 2
D2: 3,6,7,8                              # reduction candidate for 3,6
D2: 3,6 => CTR
* ..714.8252....8971..1725.4.728.5.16.4....27.8.3987125457.28..1.1....65.29.2517...
D2: 7,8                                  # 18 pairs
* PAIR E2: 3,6 COL E
E5: 3,6,1,9                              # reduction candidate for 3,6
E5: 3,6 => SOLVED
* 367149825254768931891325647728954163415632798639871254576283419183496572942517386
E5: 1,9                                  # 18 pairs
* PAIR H2: 3,7 BLK 3
G3: 3,7,6                                # reduction candidate for 3,7
G3: 3,7 => CTR
* ..714.8252..867931..1.257467284531694...1237813967825457.28...38.37.65.29.253...7
G3: 6                                    # 20 pairs
I3: 3,7,6                                # reduction candidate for 3,7
I3: 3,7                                  # 20 pairs
* PAIR H2: 3,7 ROW 2
D2: 3,7,6,8                              # reduction candidate for 3,7
D2: 3,7 => SOLVED
* 367149825254768931891325647728954163415632798639871254576283419183496572942517386
D2: 6,8                                  # 21 pairs
F2: 3,7,8                                # reduction candidate for 3,7
F2: 3,7 => CTR
* 6971438252..867931381925.4.728.5.16.4..31279813967825457.28..1981.7.65.29.25.....
F2: 8 => SOLVED
* 367149825254768931891325647728954163415632798639871254576283419183496572942517386
* PAIR H2: 3,7 COL H
H5: 3,7,9                                # reduction candidate for 3,7
H5: 3,7 => CTR
* 3671498252..8679318.1.25.4.7284531694....2378.39.7825457.28149....7965.29.2534...
H5: 9                                    # 23 pairs
H8: 3,7,1,8,9                            # reduction candidate for 3,7
H8: 3,7                                  # 28 pairs
H9: 3,7,1,8                              # reduction candidate for 3,7
H9: 3,7 => CTR
* 367149825254..7931891325.4.728.5.16.4....2..8.39.7.25457628..191437965829825.....
H9: 1,8                                  # 19 pairs
* PAIR C5: 5,6 BLK 4
B5: 5,6,1                                # reduction candidate for 5,6
B5: 5,6 => CTR
* 6971438252..867931381925.4.728.591634..31279813967825457.28.319813.965.29.253..8.
B5: 1 => SOLVED
* 367149825254768931891325647728954163415632798639871254576283419183496572942517386
* PAIR A6: 1,6 BLK 4
B5: 1,6,5                                # reduction candidate for 1,6
B5: 5 => CTR
* 697143825245867931381925746728.59163456.12..813967825457.28....8...965.296253..87
B5: 1,6                                  # 20 pairs
* PAIR D6: 6,8 COL D
D2: 6,8,3,7                              # reduction candidate for 6,8
D2: 3,7 => SOLVED
* 367149825254768931891325647728954163415632798639871254576283419183496572942517386
D2: 6,8                                  # 21 pairs
* PAIR I4: 3,9 BLK 6
H5: 3,9,7                                # reduction candidate for 3,9
H5: 7 => CTR
* 3671498252..8679318.1.25.4.7284531694....2378.39.7825457.28.......7.65.29.25.....
H5: 3,9                                  # 19 pairs
* PAIR I4: 3,9 ROW 4
D4: 3,9,4                                # reduction candidate for 3,9
D4: 3,9 => SOLVED
* 367149825254768931891325647728954163415632798639871254576283419183496572942517386
D4: 4                                    # 22 pairs
F4: 3,9,4                                # reduction candidate for 3,9
F4: 3,9                                  # 22 pairs
* PAIR I4: 3,9 COL I
I7: 3,9,6                                # reduction candidate for 3,9
I7: 6 => CTR
* 6971438252...6.9313819256477283541694.6..2..8.39.7.25457.28...6.....65.29625...8.
I7: 3,9                                  # 21 pairs
* PAIR G5: 3,7 BLK 6
H5: 3,7,9                                # reduction candidate for 3,7
H5: 3,7 => CTR
* 3671498252..8679318.1.25.4.7284531694....2378.39.7825457.28149....7965.29.2534...
H5: 9                                    # 23 pairs
* PAIR G5: 3,7 COL G
G3: 3,7,6                                # reduction candidate for 3,7
G3: 3,7 => CTR
* ..714.8252..867931..1.257467284531694...1237813967825457.28...38.37.65.29.253...7
G3: 6                                    # 20 pairs
G9: 3,7,4,6                              # reduction candidate for 3,7
G9: 3,7                                  # 23 pairs
* PAIR A8: 1,8 BLK 7
B8: 1,8,4                                # reduction candidate for 1,8
B8: 1,8                                  # 23 pairs
B9: 1,8,4,6                              # reduction candidate for 1,8
B9: 1,8                                  # 24 pairs
* PAIR A8: 1,8 ROW 8
H8: 1,8,3,7,9                            # reduction candidate for 1,8
H8: 1,8 => CTR
* 697143825254867931381925.4.7284591634...12..813967825457.28....843796512912534.8.
H8: 3,7,9                                # 20 pairs
* PAIR C8: 3,4 BLK 7
C7: 3,4,6                                # reduction candidate for 3,4
C7: 3,4 => CTR
* 6971438252.5867931381925.4.728.5.16.45631279813967825457.28..1981.7.65.29625...8.
C7: 6                                    # 20 pairs
* PAIR C8: 3,4 ROW 8
D8: 3,4,7,9                              # reduction candidate for 3,4
D8: 3,4 => SOLVED
* 367149825254768931891325647728954163415632798639871254576283419183496572942517386
D8: 7,9                                  # 23 pairs
* PAIR E9: 1,3 BLK 8
F7: 1,3,4,9                              # reduction candidate for 1,3
F7: 1,3                                  # 21 pairs
E8: 1,3,9                                # reduction candidate for 1,3
E8: 1,3 => CTR
* ..714.8252...689.1891.25.4.728.5.169415692..863987125457.28..1.1...365929.251..8.
E8: 9                                    # 18 pairs
F9: 1,3,4,7                              # reduction candidate for 1,3
F9: 1,3 => CTR
* ..714.8252..867931..1.25.4.72845.16.4...12..813967825457.284.198..7.65.29.25.....
F9: 4,7                                  # 19 pairs
* PAIR E9: 1,3 ROW 9
H9: 1,3,7,8                              # reduction candidate for 1,3
H9: 1,3 => CTR
* 367149825254..7931891325.4.72845.16.4....2..8.39.7.25457628....1437965829825.....
H9: 7,8                                  # 19 pairs
* PAIR E9: 1,3 COL E
E5: 1,3,6,9                              # reduction candidate for 1,3
E5: 6,9 => CTR
* 367149825254.38971891725.4.728.5.16.415.6279863987125457628..191.34965829.251....
E5: 1,3                                  # 18 pairs
* INCONCLUSIVE
* SAVE PR GRAPH zz-www.sudokuoftheday.co.uk-20190403-absurd-base-pr-000.dot
* REASONING
* DIS # D3: 7 => CTR => D3: 3,9
* PRF # F7: 3,9 => SOL
* DIS # D2: 3,6 => CTR => D2: 7,8
* PRF # E5: 3,6 => SOL
* DIS # G3: 3,7 => CTR => G3: 6
* PRF # D2: 3,7 => SOL
* DIS # F2: 3,7 => CTR => F2: 8
* PRF # F2: 8 => SOL
* DIS # H5: 3,7 => CTR => H5: 9
* DIS # H9: 3,7 => CTR => H9: 1,8
* DIS # B5: 5,6 => CTR => B5: 1
* PRF # B5: 1 => SOL
* DIS # B5: 5 => CTR => B5: 1,6
* PRF # D2: 3,7 => SOL
* DIS # H5: 7 => CTR => H5: 3,9
* PRF # D4: 3,9 => SOL
* DIS # I7: 6 => CTR => I7: 3,9
* DIS # H5: 3,7 => CTR => H5: 9
* DIS # G3: 3,7 => CTR => G3: 6
* DIS # H8: 1,8 => CTR => H8: 3,7,9
* DIS # C7: 3,4 => CTR => C7: 6
* PRF # D8: 3,4 => SOL
* DIS # E8: 1,3 => CTR => E8: 9
* DIS # F9: 1,3 => CTR => F9: 4,7
* DIS # H9: 1,3 => CTR => H9: 7,8
* DIS # E5: 6,9 => CTR => E5: 1,3
* CNT  26 HDP CHAINS /  56 HYP OPENED

--------------------------------------------------
* PREPARE PR GRAPH
* PAIR REDUCTION ..
* LEVEL 0 PASS 1 ROUND 1 (AUTO SOLVE) (A1,A3,A6,A8,B1,B2,B3,C2,C5,C8,D6,E2,E9,F1,F6,G5,H2,I4)
* ..714.8252.....9.1..1.25.4.728.5.16.4....2..8.39.7.25457.28.........65.29.25.....
* PAIR F1: 3,9 BLK 2
D3: 3,9,7                                # reduction candidate for 3,9
D3: 7 => CTR
* ..71498252.....9.1.91725.4.728.5.16.4....2..8.39.7.25457.28.........65729.25.7.8.
* PAIR F1: 3,9 COL F
F4: 3,9,4                                # reduction candidate for 3,9
F4: 3,9                                  # 26 pairs
F7: 3,9,1,4                              # reduction candidate for 3,9
F7: 3,9 => SOLVED
* 367149825254768931891325647728954163415632798639871254576283419183496572942517386
* DURATION: 0:00:03.623509  START: 05:03:31.758390  END: 05:03:35.381899 2019-05-01
* SOLUTION FOUND
* SAVE PR GRAPH zz-www.sudokuoftheday.co.uk-20190403-absurd-base-pr-001.dot
* REASONING
* DIS # D3: 7 => CTR => D3: 3,9
* PRF D3: 3,9 # F7: 3,9 => SOL
* STA D3: 3,9 + F7: 3,9
* CNT   2 HDP CHAINS /   4 HYP OPENED

Header Info

http://www.sudokuoftheday.co.uk/cgi-bin/sudoku1280.cgi?ACTION=archive2&USER=&MONTH=Apr&YEAR=2019, 20190403, absurd

Solution

position: 367149825254768931891325647728954163415632798639871254576283419183496572942517386 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 # D3: 3,9 => UNS
* DIS # D3: 7 => CTR => D3: 3,9
* INC # F4: 3,9 => UNS
* PRF # F7: 3,9 => SOL
* INC # F7: 1,4 => UNS
* DIS # D2: 3,6 => CTR => D2: 7,8
* INC # D2: 7,8 => UNS
* PRF # E5: 3,6 => SOL
* INC # E5: 1,9 => UNS
* DIS # G3: 3,7 => CTR => G3: 6
* INC # G3: 6 => UNS
* INC # I3: 3,7 => UNS
* PRF # D2: 3,7 => SOL
* INC # D2: 6,8 => UNS
* DIS # F2: 3,7 => CTR => F2: 8
* PRF # F2: 8 => SOL
* DIS # H5: 3,7 => CTR => H5: 9
* INC # H5: 9 => UNS
* INC # H8: 3,7 => UNS
* DIS # H9: 3,7 => CTR => H9: 1,8
* INC # H9: 1,8 => UNS
* DIS # B5: 5,6 => CTR => B5: 1
* PRF # B5: 1 => SOL
* INC # B5: 1,6 => UNS
* DIS # B5: 5 => CTR => B5: 1,6
* INC # D2: 6,8 => UNS
* PRF # D2: 3,7 => SOL
* INC # H5: 3,9 => UNS
* DIS # H5: 7 => CTR => H5: 3,9
* PRF # D4: 3,9 => SOL
* INC # D4: 4 => UNS
* INC # F4: 3,9 => UNS
* INC # I7: 3,9 => UNS
* DIS # I7: 6 => CTR => I7: 3,9
* DIS # H5: 3,7 => CTR => H5: 9
* INC # H5: 9 => UNS
* DIS # G3: 3,7 => CTR => G3: 6
* INC # G3: 6 => UNS
* INC # G9: 3,7 => UNS
* INC # B8: 1,8 => UNS
* INC # B9: 1,8 => UNS
* DIS # H8: 1,8 => CTR => H8: 3,7,9
* INC # H8: 3,7,9 => UNS
* DIS # C7: 3,4 => CTR => C7: 6
* INC # C7: 6 => UNS
* PRF # D8: 3,4 => SOL
* INC # D8: 7,9 => UNS
* INC # F7: 1,3 => UNS
* DIS # E8: 1,3 => CTR => E8: 9
* INC # E8: 9 => UNS
* DIS # F9: 1,3 => CTR => F9: 4,7
* INC # F9: 4,7 => UNS
* DIS # H9: 1,3 => CTR => H9: 7,8
* INC # H9: 7,8 => UNS
* INC # E5: 1,3 => UNS
* DIS # E5: 6,9 => CTR => E5: 1,3
* CNT  56 HDP CHAINS /  56 HYP OPENED

A2. Pair Reduction

Full list of HDP chains traversed:

* INC # D3: 3,9 => UNS
* DIS # D3: 7 => CTR => D3: 3,9
* INC D3: 3,9 # F4: 3,9 => UNS
* PRF D3: 3,9 # F7: 3,9 => SOL
* STA D3: 3,9 + F7: 3,9
* CNT   4 HDP CHAINS /   4 HYP OPENED