Analysis of zz-www.sudokuoftheday.co.uk-20190217-absurd-base.sdk

Contents

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

level: medium

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

position: .78.5..3...3..92......1.6..3.9.....6..1...5..8....1947...89.4...85.6............2 initial

Autosolve

position: .78.5.13...3..92......1.6..3.9...8167.19..5238....1947...89.465.85.6..91...1.5.82 autosolve
Autosolve

Pair Reduction Variants

Pair Reduction Analysis

Pair Reduction Analysis

The following important HDP chains were detected:

* DIS # A2: 4,5 => CTR => A2: 1,6
* DIS # A3: 2,9 => CTR => A3: 4,5
* DIS # A3: 2,4 => CTR => A3: 5,9
* DIS # D3: 2,4 => CTR => D3: 3,7
* DIS # F3: 2,4 => CTR => F3: 3,7,8
* DIS # I3: 8 => CTR => I3: 4,9
* PRF # I3: 9 => SOL
* DIS # E2: 7 => CTR => E2: 4,8
* DIS # F5: 8 => CTR => F5: 4,6
* DIS # E4: 4,7 => CTR => E4: 2
* DIS # F3: 4,7 => CTR => F3: 2,3,8
* DIS # E2: 7 => CTR => E2: 4,8
* DIS # B7: 1,2 => CTR => B7: 3
* DIS # F7: 3 => CTR => F7: 2,7
* DIS # A3: 2,4 => CTR => A3: 5,9
* DIS # E9: 4 => CTR => E9: 3,7
* CNT  16 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 # A2: 4,5 => CTR => A2: 1,6
* DIS A2: 1,6 # A1: 4 => CTR => A1: 2,9
* PRF A2: 1,6 + A1: 2,9 # E2: 4,8 => SOL
* STA A2: 1,6 + A1: 2,9 + E2: 4,8
* CNT   3 HDP CHAINS /   5 HYP OPENED

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

Details

Positions

.78.5..3...3..92......1.6..3.9.....6..1...5..8....1947...89.4...85.6............2 initial
.78.5.13...3..92......1.6..3.9...8167.19..5238....1947...89.465.85.6..91...1.5.82 autosolve
978256134613749258524318679349527816761984523852631947137892465285463791496175382 solved

Classification

level: medium

Pairing Analysis

--------------------------------------------------
* PAIRS (17)
B2: 1,6
B3: 2,9
C3: 2,4
I1: 4,9
H2: 5,7
I2: 4,8
H3: 5,7
B5: 4,6
C6: 2,6
F4: 4,7
E5: 4,8
E6: 2,3
A7: 1,2
C7: 2,7
A8: 2,4
G8: 3,7
G9: 3,7

--------------------------------------------------
* CONSTRAINT PAIRS (AUTO SOLVE)
A2,B2: 1.. / A2 = 1  =>  0 pairs (X) / B2 = 1  => 17 pairs (_)
A7,B7: 1.. / A7 = 1  => 17 pairs (_) / B7 = 1  =>  0 pairs (X)
A2,A7: 1.. / A2 = 1  =>  0 pairs (X) / A7 = 1  => 17 pairs (_)
B2,B7: 1.. / B2 = 1  => 17 pairs (_) / B7 = 1  =>  0 pairs (X)
E4,E6: 2.. / E4 = 2  => 19 pairs (_) / E6 = 2  =>  0 pairs (X)
B4,E4: 2.. / B4 = 2  =>  0 pairs (X) / E4 = 2  => 19 pairs (_)
D3,F3: 3.. / D3 = 3  => 19 pairs (_) / F3 = 3  =>  0 pairs (X)
D6,E6: 3.. / D6 = 3  =>  0 pairs (X) / E6 = 3  => 19 pairs (_)
B7,B9: 3.. / B7 = 3  => 18 pairs (_) / B9 = 3  =>  0 pairs (X)
G8,G9: 3.. / G8 = 3  => 17 pairs (_) / G9 = 3  => 18 pairs (_)
B7,F7: 3.. / B7 = 3  => 18 pairs (_) / F7 = 3  =>  0 pairs (X)
E6,E9: 3.. / E6 = 3  => 19 pairs (_) / E9 = 3  =>  0 pairs (X)
B4,B5: 4.. / B4 = 4  => 18 pairs (_) / B5 = 4  => 19 pairs (_)
C3,C9: 4.. / C3 = 4  => 18 pairs (_) / C9 = 4  =>  0 pairs (X)
A2,A3: 5.. / A2 = 5  =>  0 pairs (X) / A3 = 5  => 15 pairs (_)
H2,H3: 5.. / H2 = 5  => 15 pairs (_) / H3 = 5  =>  0 pairs (X)
B4,B6: 5.. / B4 = 5  => 19 pairs (_) / B6 = 5  => 19 pairs (_)
D4,D6: 5.. / D4 = 5  => 19 pairs (_) / D6 = 5  => 19 pairs (_)
A2,H2: 5.. / A2 = 5  =>  0 pairs (X) / H2 = 5  => 15 pairs (_)
A3,H3: 5.. / A3 = 5  => 15 pairs (_) / H3 = 5  =>  0 pairs (X)
B4,D4: 5.. / B4 = 5  => 19 pairs (_) / D4 = 5  => 19 pairs (_)
B6,D6: 5.. / B6 = 5  => 19 pairs (_) / D6 = 5  => 19 pairs (_)
F5,D6: 6.. / F5 = 6  => 19 pairs (_) / D6 = 6  => 18 pairs (_)
B5,F5: 6.. / B5 = 6  => 18 pairs (_) / F5 = 6  => 19 pairs (_)
C6,C9: 6.. / C6 = 6  =>  0 pairs (X) / C9 = 6  => 21 pairs (_)
F1,F5: 6.. / F1 = 6  => 18 pairs (_) / F5 = 6  => 19 pairs (_)
H2,H3: 7.. / H2 = 7  =>  0 pairs (X) / H3 = 7  => 15 pairs (_)
C7,C9: 7.. / C7 = 7  => 18 pairs (_) / C9 = 7  =>  0 pairs (X)
G8,G9: 7.. / G8 = 7  => 18 pairs (_) / G9 = 7  => 17 pairs (_)
C7,F7: 7.. / C7 = 7  => 18 pairs (_) / F7 = 7  =>  0 pairs (X)
E2,F3: 8.. / E2 = 8  =>  0 pairs (X) / F3 = 8  => 20 pairs (_)
I2,I3: 8.. / I2 = 8  => 20 pairs (_) / I3 = 8  =>  0 pairs (X)
E5,F5: 8.. / E5 = 8  => 20 pairs (_) / F5 = 8  =>  0 pairs (X)
E2,I2: 8.. / E2 = 8  =>  0 pairs (X) / I2 = 8  => 20 pairs (_)
F3,I3: 8.. / F3 = 8  => 20 pairs (_) / I3 = 8  =>  0 pairs (X)
E2,E5: 8.. / E2 = 8  =>  0 pairs (X) / E5 = 8  => 20 pairs (_)
F3,F5: 8.. / F3 = 8  => 20 pairs (_) / F5 = 8  =>  0 pairs (X)
I1,I3: 9.. / I1 = 9  => 17 pairs (_) / I3 = 9  =>  0 pairs (*)
A9,B9: 9.. / A9 = 9  => 16 pairs (_) / B9 = 9  => 20 pairs (_)
A1,I1: 9.. / A1 = 9  =>  0 pairs (*) / I1 = 9  =>  0 pairs (X)
B3,B9: 9.. / B3 = 9  => 16 pairs (_) / B9 = 9  => 20 pairs (_)
* DURATION: 0:00:49.567665  START: 03:47:51.513927  END: 03:48:41.081592 2019-05-01
* CP COUNT: (41)
* SOLUTION FOUND

--------------------------------------------------
* PREPARE PR GRAPH
* PAIR REDUCTION ..
* LEVEL 0 PASS 1 ROUND 1 (AUTO SOLVE) (A7,A8,B2,B3,B5,C3,C6,C7,E5,E6,F4,G8,G9,H2,H3,I1,I2)
* .78.5.13...3..92......1.6..3.9...8167.19..5238....1947...89.465.85.6..91...1.5.82
* PAIR B2: 1,6 BLK 1
A2: 1,6,4,5                              # reduction candidate for 1,6
A2: 4,5 => CTR
* 678.5.1394136792585923186743.9.478167419865238....19471..89.465.85.6..91..41.5.82
A2: 1,6                                  # 17 pairs
* PAIR B3: 2,9 BLK 1
A1: 2,9,4,6                              # reduction candidate for 2,9
A1: 2,9                                  # 20 pairs
A3: 2,9,4,5                              # reduction candidate for 2,9
A3: 2,9 => CTR
* 678.5.1395136.927...4.1865.3.9...8167.19.65238....19471..89.465.85.6..91...1.5.82
A3: 4,5                                  # 18 pairs
* PAIR C3: 2,4 BLK 1
A1: 2,4,6,9                              # reduction candidate for 2,4
A1: 2,4                                  # 16 pairs
A3: 2,4,5,9                              # reduction candidate for 2,4
A3: 2,4 => CTR
* 678.5.1395136.927..9..186543.9...8167.19.65238....19471..89.465.85.6..91...1.5.82
A3: 5,9                                  # 18 pairs
* PAIR C3: 2,4 ROW 3
D3: 2,4,3,7                              # reduction candidate for 2,4
D3: 2,4 => CTR
* .78.5613961378925459..136783.9...8167.19.85238..631947.3.89.465.8536.791..6175382
D3: 3,7                                  # 18 pairs
F3: 2,4,3,7,8                            # reduction candidate for 2,4
F3: 2,4 => CTR
* .78.5613961378925459.31.6783.9...8167.19485238..631947...89.465.85.6..91..6175382
F3: 3,7,8                                # 17 pairs
* PAIR I1: 4,9 BLK 3
I3: 4,9,8                                # reduction candidate for 4,9
I3: 8 => CTR
* .78.56139613789254594.1.6783.95278167619485238526319471..89.465.85.6..91..61.5.82
I3: 4,9                                  # 20 pairs
* PAIR I1: 4,9 ROW 1
A1: 4,9,2,6                              # reduction candidate for 4,9
A1: 4,9                                  # 23 pairs
A1: 2,6                                  # 20 pairs
* PAIR I2: 4,8 BLK 3
I3: 4,8,9                                # reduction candidate for 4,8
I3: 9 => SOLVED
* 978256134613749258524318679349527816761984523852631947137892465285463791496175382
I3: 4,8                                  # 17 pairs
* PAIR I2: 4,8 ROW 2
E2: 4,8,7                                # reduction candidate for 4,8
E2: 7 => CTR
* 978.5.134..34792585243186793.9.2.8167.198.5238.2.319472..89.465485.6..91.9.145382
E2: 4,8                                  # 22 pairs
* PAIR B5: 4,6 ROW 5
F5: 4,6,8                                # reduction candidate for 4,6
F5: 8 => CTR
* .78.5613.613.892545.4.1.678349527816761948523852631947137892465285.64791496175382
F5: 4,6                                  # 20 pairs
* PAIR C6: 2,6 BLK 4
B6: 2,6,5                                # reduction candidate for 2,6
B6: 5                                    # 19 pairs
B6: 2,6                                  # 19 pairs
* PAIR F4: 4,7 BLK 5
D4: 4,7,5                                # reduction candidate for 4,7
D4: 4,7                                  # 19 pairs
E4: 4,7,2                                # reduction candidate for 4,7
E4: 4,7 => CTR
* .78.5.13...3..92......1.6..3295..816741986523856321947...89.465.85.6..91...135782
E4: 2                                    # 19 pairs
* PAIR F4: 4,7 COL F
F3: 4,7,2,3,8                            # reduction candidate for 4,7
F3: 4,7 => CTR
* .78.5613961378925459.31.6.83.9...8167.19485238..631947...89.465.85.6..91..6175382
F3: 2,3,8                                # 17 pairs
F8: 4,7,2,3                              # reduction candidate for 4,7
F8: 4,7                                  # 21 pairs
* PAIR E5: 4,8 BLK 5
F5: 4,8,6                                # reduction candidate for 4,8
F5: 6                                    # 19 pairs
F5: 4,8                                  # 18 pairs
* PAIR E5: 4,8 COL E
E2: 4,8,7                                # reduction candidate for 4,8
E2: 7 => CTR
* 978.5.134..34792585243186793.9.2.8167.198.5238.2.319472..89.465485.6..91.9.145382
E2: 4,8                                  # 22 pairs
* PAIR A7: 1,2 BLK 7
B7: 1,2,3                                # reduction candidate for 1,2
B7: 1,2 => CTR
* .78.5.139..3..92...9431.6.83.9.2.8167.198.5238...31947..7893465.85.6.391936145782
B7: 3                                    # 18 pairs
* PAIR C7: 2,7 ROW 7
F7: 2,7,3                                # reduction candidate for 2,7
F7: 3 => CTR
* .78.5.139..3..92...9431.6.83.9.2.8167.198.5238...31947..7893465.85.6.391936145782
F7: 2,7                                  # 18 pairs
* PAIR A8: 2,4 ROW 8
D8: 2,4,3,7                              # reduction candidate for 2,4
D8: 2,4                                  # 19 pairs
F8: 2,4,3,7                              # reduction candidate for 2,4
F8: 2,4                                  # 20 pairs
* PAIR A8: 2,4 COL A
A1: 2,4,6,9                              # reduction candidate for 2,4
A1: 2,4                                  # 16 pairs
A3: 2,4,5,9                              # reduction candidate for 2,4
A3: 2,4 => CTR
* 678.5.1395136.927..9..186543.9...8167.19.65238....19471..89.465.85.6..91...1.5.82
A3: 5,9                                  # 18 pairs
* PAIR G8: 3,7 ROW 8
D8: 3,7,2,4                              # reduction candidate for 3,7
D8: 3,7                                  # 20 pairs
F8: 3,7,2,4                              # reduction candidate for 3,7
F8: 3,7                                  # 19 pairs
* PAIR G9: 3,7 ROW 9
E9: 3,7,4                                # reduction candidate for 3,7
E9: 4 => CTR
* 978.5.134..34792585243186793.9.2.8167.198.5238.2.319472..89.465485.6..91.9.145382
E9: 3,7                                  # 18 pairs
* INCONCLUSIVE
* SAVE PR GRAPH zz-www.sudokuoftheday.co.uk-20190217-absurd-base-pr-000.dot
* REASONING
* DIS # A2: 4,5 => CTR => A2: 1,6
* DIS # A3: 2,9 => CTR => A3: 4,5
* DIS # A3: 2,4 => CTR => A3: 5,9
* DIS # D3: 2,4 => CTR => D3: 3,7
* DIS # F3: 2,4 => CTR => F3: 3,7,8
* DIS # I3: 8 => CTR => I3: 4,9
* PRF # I3: 9 => SOL
* DIS # E2: 7 => CTR => E2: 4,8
* DIS # F5: 8 => CTR => F5: 4,6
* DIS # E4: 4,7 => CTR => E4: 2
* DIS # F3: 4,7 => CTR => F3: 2,3,8
* DIS # E2: 7 => CTR => E2: 4,8
* DIS # B7: 1,2 => CTR => B7: 3
* DIS # F7: 3 => CTR => F7: 2,7
* DIS # A3: 2,4 => CTR => A3: 5,9
* DIS # E9: 4 => CTR => E9: 3,7
* CNT  16 HDP CHAINS /  47 HYP OPENED

--------------------------------------------------
* PREPARE PR GRAPH
* PAIR REDUCTION ..
* LEVEL 0 PASS 1 ROUND 1 (AUTO SOLVE) (A7,A8,B2,B3,B5,C3,C6,C7,E5,E6,F4,G8,G9,H2,H3,I1,I2)
* .78.5.13...3..92......1.6..3.9...8167.19..5238....1947...89.465.85.6..91...1.5.82
* PAIR B2: 1,6 BLK 1
A2: 1,6,4,5                              # reduction candidate for 1,6
A2: 4,5 => CTR
* 678.5.1394136792585923186743.9.478167419865238....19471..89.465.85.6..91..41.5.82
* PAIR B3: 2,9 BLK 1
A1: 2,9,4                                # reduction candidate for 2,9
A1: 4 => CTR
* 478.5.139..3..925.592.1.67.3.9...8167.19..5238.6..1947..789.465285.6..919641.5.82
* PAIR I2: 4,8 ROW 2
E2: 4,8,7                                # reduction candidate for 4,8
E2: 4,8 => SOLVED
* 978256134613749258524318679349527816761984523852631947137892465285463791496175382
* DURATION: 0:00:04.288976  START: 03:49:10.554819  END: 03:49:14.843795 2019-05-01
* SOLUTION FOUND
* SAVE PR GRAPH zz-www.sudokuoftheday.co.uk-20190217-absurd-base-pr-001.dot
* REASONING
* DIS # A2: 4,5 => CTR => A2: 1,6
* DIS A2: 1,6 # A1: 4 => CTR => A1: 2,9
* PRF A2: 1,6 + A1: 2,9 # E2: 4,8 => SOL
* STA A2: 1,6 + A1: 2,9 + E2: 4,8
* CNT   3 HDP CHAINS /   5 HYP OPENED

Header Info

http://www.sudokuoftheday.co.uk/cgi-bin/sudoku1280.cgi?ACTION=archive2&USER=&MONTH=Feb&YEAR=2019, 20190217, absurd

Solution

position: 978256134613749258524318679349527816761984523852631947137892465285463791496175382 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 # A2: 1,6 => UNS
* DIS # A2: 4,5 => CTR => A2: 1,6
* INC # A1: 2,9 => UNS
* DIS # A3: 2,9 => CTR => A3: 4,5
* INC # A3: 4,5 => UNS
* INC # A1: 2,4 => UNS
* DIS # A3: 2,4 => CTR => A3: 5,9
* INC # A3: 5,9 => UNS
* DIS # D3: 2,4 => CTR => D3: 3,7
* INC # D3: 3,7 => UNS
* DIS # F3: 2,4 => CTR => F3: 3,7,8
* INC # F3: 3,7,8 => UNS
* INC # I3: 4,9 => UNS
* DIS # I3: 8 => CTR => I3: 4,9
* INC # A1: 4,9 => UNS
* INC # A1: 2,6 => UNS
* INC # I3: 4,8 => UNS
* PRF # I3: 9 => SOL
* INC # E2: 4,8 => UNS
* DIS # E2: 7 => CTR => E2: 4,8
* INC # F5: 4,6 => UNS
* DIS # F5: 8 => CTR => F5: 4,6
* INC # B6: 2,6 => UNS
* INC # B6: 5 => UNS
* INC # D4: 4,7 => UNS
* DIS # E4: 4,7 => CTR => E4: 2
* INC # E4: 2 => UNS
* DIS # F3: 4,7 => CTR => F3: 2,3,8
* INC # F3: 2,3,8 => UNS
* INC # F8: 4,7 => UNS
* INC # F5: 4,8 => UNS
* INC # F5: 6 => UNS
* INC # E2: 4,8 => UNS
* DIS # E2: 7 => CTR => E2: 4,8
* DIS # B7: 1,2 => CTR => B7: 3
* INC # B7: 3 => UNS
* INC # F7: 2,7 => UNS
* DIS # F7: 3 => CTR => F7: 2,7
* INC # D8: 2,4 => UNS
* INC # F8: 2,4 => UNS
* INC # A1: 2,4 => UNS
* DIS # A3: 2,4 => CTR => A3: 5,9
* INC # A3: 5,9 => UNS
* INC # D8: 3,7 => UNS
* INC # F8: 3,7 => UNS
* INC # E9: 3,7 => UNS
* DIS # E9: 4 => CTR => E9: 3,7
* CNT  47 HDP CHAINS /  47 HYP OPENED

A2. Pair Reduction

Full list of HDP chains traversed:

* INC # A2: 1,6 => UNS
* DIS # A2: 4,5 => CTR => A2: 1,6
* INC A2: 1,6 # A1: 2,9 => UNS
* DIS A2: 1,6 # A1: 4 => CTR => A1: 2,9
* PRF A2: 1,6 + A1: 2,9 # E2: 4,8 => SOL
* STA A2: 1,6 + A1: 2,9 + E2: 4,8
* CNT   5 HDP CHAINS /   5 HYP OPENED