Analysis of zz-www.sudokuoftheday.co.uk-20190313-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: ..856...95....2...2......45786.5.......7...1....2.6..8.936.....65.3.1...8.7...9.. initial

Autosolve

position: ..856...95....2...2......4578615.....2.7...1....2.6..84936.....652391...8174259.. autosolve
Autosolve

Pair Reduction Variants

Pair Reduction Analysis

Pair Reduction Analysis

The following important HDP chains were detected:

* DIS # G1: 2,7 => CTR => G1: 1,3
* PRF # C2: 1,9 => SOL
* DIS # C2: 4 => CTR => C2: 1,9
* DIS # F1: 3,7 => CTR => F1: 4
* DIS # F5: 4,8 => CTR => F5: 3,9
* DIS # G5: 3,6 => CTR => G5: 4,5
* DIS # F4: 3,4 => CTR => F4: 9
* PRF # F4: 9 => SOL
* DIS # E5: 3,4 => CTR => E5: 8
* PRF # F5: 3,4 => SOL
* DIS # H6: 5,7 => CTR => H6: 9
* PRF # H6: 9 => SOL
* DIS # G7: 1 => CTR => G7: 2,5
* DIS # G7: 5 => CTR => G7: 1,2
* DIS # I2: 3,6 => CTR => I2: 1,7
* CNT  15 HDP CHAINS /  41 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 # G1: 2,7 => CTR => G1: 1,3
* PRF G1: 1,3 # C2: 1,9 => SOL
* STA G1: 1,3 + C2: 1,9
* CNT   2 HDP CHAINS /   3 HYP OPENED

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

Details

Positions

..856...95....2...2......45786.5.......7...1....2.6..8.936.....65.3.1...8.7...9.. initial
..856...95....2...2......4578615.....2.7...1....2.6..84936.....652391...8174259.. autosolve
378564129541932687269817345786159432924783516135246798493678251652391874817425963 solved

Classification

level: medium

Pairing Analysis

--------------------------------------------------
* PAIRS (20)
A1: 1,3
C3: 1,9
D2: 8,9
D3: 8,9
F3: 3,7
A5: 3,9
C5: 4,5
A6: 1,9
B6: 3,4
C6: 1,5
E6: 3,4
G6: 5,7
E7: 7,8
F7: 7,8
H7: 2,5
I7: 1,2
H8: 7,8
I8: 4,7
H9: 3,6
I9: 3,6

--------------------------------------------------
* CONSTRAINT PAIRS (AUTO SOLVE)
E2,E3: 1.. / E2 = 1  => 28 pairs (_) / E3 = 1  => 18 pairs (_)
A6,C6: 1.. / A6 = 1  =>  0 pairs (*) / C6 = 1  =>  0 pairs (X)
G7,I7: 1.. / G7 = 1  =>  0 pairs (X) / I7 = 1  => 22 pairs (_)
A1,G1: 1.. / A1 = 1  =>  0 pairs (X) / G1 = 1  =>  0 pairs (_)
A1,A6: 1.. / A1 = 1  =>  0 pairs (X) / A6 = 1  =>  0 pairs (_)
I2,I7: 1.. / I2 = 1  =>  0 pairs (X) / I7 = 1  => 22 pairs (_)
G1,H1: 2.. / G1 = 2  =>  0 pairs (X) / H1 = 2  => 22 pairs (_)
I4,I7: 2.. / I4 = 2  => 22 pairs (_) / I7 = 2  =>  0 pairs (X)
A5,B6: 3.. / A5 = 3  =>  0 pairs (X) / B6 = 3  =>  0 pairs (_)
H9,I9: 3.. / H9 = 3  =>  0 pairs (X) / I9 = 3  => 20 pairs (_)
B6,E6: 3.. / B6 = 3  =>  0 pairs (*) / E6 = 3  =>  0 pairs (X)
A1,A5: 3.. / A1 = 3  =>  0 pairs (*) / A5 = 3  =>  0 pairs (X)
F1,E2: 4.. / F1 = 4  => 25 pairs (_) / E2 = 4  =>  0 pairs (X)
C5,B6: 4.. / C5 = 4  =>  0 pairs (*) / B6 = 4  =>  0 pairs (X)
G8,I8: 4.. / G8 = 4  => 19 pairs (_) / I8 = 4  => 26 pairs (_)
B1,F1: 4.. / B1 = 4  =>  0 pairs (X) / F1 = 4  => 25 pairs (_)
B6,E6: 4.. / B6 = 4  =>  0 pairs (X) / E6 = 4  =>  0 pairs (_)
C2,C5: 4.. / C2 = 4  =>  0 pairs (X) / C5 = 4  =>  0 pairs (_)
C5,C6: 5.. / C5 = 5  =>  0 pairs (X) / C6 = 5  =>  0 pairs (_)
G7,H7: 5.. / G7 = 5  =>  0 pairs (X) / H7 = 5  => 21 pairs (_)
C5,G5: 5.. / C5 = 5  =>  0 pairs (X) / G5 = 5  =>  0 pairs (_)
H6,H7: 5.. / H6 = 5  =>  0 pairs (X) / H7 = 5  => 21 pairs (_)
B2,B3: 6.. / B2 = 6  => 19 pairs (_) / B3 = 6  => 20 pairs (_)
G5,I5: 6.. / G5 = 6  =>  0 pairs (X) / I5 = 6  => 20 pairs (_)
H9,I9: 6.. / H9 = 6  => 20 pairs (_) / I9 = 6  =>  0 pairs (X)
B3,G3: 6.. / B3 = 6  => 20 pairs (_) / G3 = 6  => 19 pairs (_)
H2,H9: 6.. / H2 = 6  =>  0 pairs (X) / H9 = 6  => 20 pairs (_)
G6,H6: 7.. / G6 = 7  => 21 pairs (_) / H6 = 7  =>  0 pairs (X)
E7,F7: 7.. / E7 = 7  => 19 pairs (_) / F7 = 7  =>  0 pairs (X)
I2,I8: 7.. / I2 = 7  => 26 pairs (_) / I8 = 7  => 19 pairs (_)
D2,D3: 8.. / D2 = 8  =>  0 pairs (X) / D3 = 8  => 18 pairs (_)
E5,F5: 8.. / E5 = 8  => 19 pairs (_) / F5 = 8  =>  0 pairs (X)
E7,F7: 8.. / E7 = 8  =>  0 pairs (X) / F7 = 8  => 19 pairs (_)
G8,H8: 8.. / G8 = 8  => 19 pairs (_) / H8 = 8  => 20 pairs (_)
D3,G3: 8.. / D3 = 8  => 18 pairs (_) / G3 = 8  =>  0 pairs (X)
E5,E7: 8.. / E5 = 8  => 19 pairs (_) / E7 = 8  =>  0 pairs (X)
F5,F7: 8.. / F5 = 8  =>  0 pairs (X) / F7 = 8  => 19 pairs (_)
H2,H8: 8.. / H2 = 8  => 19 pairs (_) / H8 = 8  => 20 pairs (_)
C2,C3: 9.. / C2 = 9  =>  0 pairs (X) / C3 = 9  => 18 pairs (_)
D2,D3: 9.. / D2 = 9  => 18 pairs (_) / D3 = 9  =>  0 pairs (X)
A5,A6: 9.. / A5 = 9  =>  0 pairs (*) / A6 = 9  =>  0 pairs (X)
F4,F5: 9.. / F4 = 9  =>  0 pairs (*) / F5 = 9  =>  0 pairs (X)
H4,H6: 9.. / H4 = 9  =>  0 pairs (X) / H6 = 9  =>  0 pairs (_)
C2,D2: 9.. / C2 = 9  =>  0 pairs (X) / D2 = 9  => 18 pairs (_)
C3,D3: 9.. / C3 = 9  => 18 pairs (_) / D3 = 9  =>  0 pairs (X)
F4,H4: 9.. / F4 = 9  =>  0 pairs (*) / H4 = 9  =>  0 pairs (X)
A5,F5: 9.. / A5 = 9  =>  0 pairs (*) / F5 = 9  =>  0 pairs (X)
A6,H6: 9.. / A6 = 9  =>  0 pairs (X) / H6 = 9  =>  0 pairs (_)
* DURATION: 0:01:11.938107  START: 04:28:47.429271  END: 04:29:59.367378 2019-05-01
* CP COUNT: (48)
* SOLUTION FOUND

--------------------------------------------------
* PREPARE PR GRAPH
* PAIR REDUCTION ..
* LEVEL 0 PASS 1 ROUND 1 (AUTO SOLVE) (A1,A5,A6,B6,C3,C5,C6,D2,D3,E6,E7,F3,F7,G6,H7,H8,H9,I7,I8,I9)
* ..856...95....2...2......4578615.....2.7...1....2.6..84936.....652391...8174259..
* PAIR A1: 1,3 ROW 1
G1: 1,3,2,7                              # reduction candidate for 1,3
G1: 2,7 => CTR
* 1.8564..95....2...2.98...4578615....32.7.9.1.941236..84936.8...652391...8174259..
G1: 1,3                                  # 25 pairs
* PAIR C3: 1,9 BLK 1
C2: 1,9,4                                # reduction candidate for 1,9
C2: 1,9 => SOLVED
* 378564129541932687269817345786159432924783516135246798493678251652391874817425963
C2: 4 => CTR
* 1.8564..95.49.2...2.98.3.45786159....257...1..41236..84936.....652391...8174259..
* PAIR F3: 3,7 BLK 2
F1: 3,7,4                                # reduction candidate for 3,7
F1: 3,7 => CTR
* .4856...95...42...2...1..4578615.....247..516.3.2.6..84936.....652391...8174259..
F1: 4                                    # 25 pairs
E2: 3,7,1,4                              # reduction candidate for 3,7
E2: 3,7                                  # 24 pairs
E3: 3,7,1                                # reduction candidate for 3,7
E3: 3,7                                  # 28 pairs
* PAIR F3: 3,7 ROW 3
B3: 3,7,6                                # reduction candidate for 3,7
B3: 3,7                                  # 19 pairs
G3: 3,7,1,6,8                            # reduction candidate for 3,7
G3: 3,7                                  # 19 pairs
* PAIR A5: 3,9 ROW 5
F5: 3,9,4,8                              # reduction candidate for 3,9
F5: 4,8 => CTR
* 3.856412954...2...26...3845786159.3.92473851613524679849368725.652391...8174259..
F5: 3,9                                  # 22 pairs
* PAIR C5: 4,5 ROW 5
G5: 4,5,3,6                              # reduction candidate for 4,5
G5: 3,6 => CTR
* 1.8564..95.49.2...2.98.3.45786159....257...1..41236..84936.....652391...8174259..
G5: 4,5                                  # 23 pairs
* PAIR B6: 3,4 COL B
B1: 3,4,7                                # reduction candidate for 3,4
B1: 3,4                                  # 25 pairs
B2: 3,4,6,7                              # reduction candidate for 3,4
B2: 3,4                                  # 26 pairs
* PAIR E6: 3,4 BLK 5
F4: 3,4,9                                # reduction candidate for 3,4
F4: 3,4 => CTR
* 1.8564..95....2...2.98...4578615..9.325789.1.941236..8493678...652391...8174259..
F4: 9 => SOLVED
* 378564129541932687269817345786159432924783516135246798493678251652391874817425963
E5: 3,4,8                                # reduction candidate for 3,4
E5: 3,4 => CTR
* 3.856412954...2...26..73845786159.3.92473851613524679849368725.652391...8174259..
E5: 8                                    # 19 pairs
F5: 3,4,8,9                              # reduction candidate for 3,4
F5: 3,4 => SOLVED
* 378564129541932687269817345786159432924783516135246798493678251652391874817425963
F5: 8,9                                  # 21 pairs
* PAIR E6: 3,4 COL E
E2: 3,4,1,7                              # reduction candidate for 3,4
E2: 1,7                                  # 28 pairs
E2: 3,4                                  # 17 pairs
* PAIR G6: 5,7 BLK 6
H6: 5,7,9                                # reduction candidate for 5,7
H6: 5,7 => CTR
* 1.8564..95....2...2.98...4578615..9.325789.1.941236..8493678...652391...8174259..
H6: 9 => SOLVED
* 378564129541932687269817345786159432924783516135246798493678251652391874817425963
* PAIR H7: 2,5 BLK 9
G7: 2,5,1                                # reduction candidate for 2,5
G7: 1 => CTR
* 1.8564..95....2..12.981..4578615....32.7.9.1.9412365784936.8152652391.878174259..
G7: 2,5                                  # 22 pairs
* PAIR I7: 1,2 BLK 9
G7: 1,2,5                                # reduction candidate for 1,2
G7: 5 => CTR
* 1.85642.95.49.2...2.98.3.45786159432.257...1..412367584936..521652391...8174259..
G7: 1,2                                  # 21 pairs
* PAIR H8: 7,8 BLK 9
G8: 7,8,4                                # reduction candidate for 7,8
G8: 7,8                                  # 26 pairs
G8: 4                                    # 19 pairs
* PAIR H8: 7,8 COL H
H2: 7,8,3,6                              # reduction candidate for 7,8
H2: 7,8                                  # 25 pairs
H2: 3,6                                  # 23 pairs
* PAIR I8: 4,7 BLK 9
G8: 4,7,8                                # reduction candidate for 4,7
G8: 4,7                                  # 20 pairs
G8: 8                                    # 19 pairs
* PAIR H9: 3,6 COL H
H2: 3,6,7,8                              # reduction candidate for 3,6
H2: 7,8                                  # 25 pairs
H2: 3,6                                  # 23 pairs
* PAIR I9: 3,6 COL I
I2: 3,6,1,7                              # reduction candidate for 3,6
I2: 3,6 => CTR
* ..8564..95.49.28..2.98.3.457861593.2.2.7...14.4.236..84936....16523914878174259..
I2: 1,7                                  # 21 pairs
I5: 3,6,4                                # reduction candidate for 3,6
I5: 3,6                                  # 23 pairs
* INCONCLUSIVE
* SAVE PR GRAPH zz-www.sudokuoftheday.co.uk-20190313-absurd-base-pr-000.dot
* REASONING
* DIS # G1: 2,7 => CTR => G1: 1,3
* PRF # C2: 1,9 => SOL
* DIS # C2: 4 => CTR => C2: 1,9
* DIS # F1: 3,7 => CTR => F1: 4
* DIS # F5: 4,8 => CTR => F5: 3,9
* DIS # G5: 3,6 => CTR => G5: 4,5
* DIS # F4: 3,4 => CTR => F4: 9
* PRF # F4: 9 => SOL
* DIS # E5: 3,4 => CTR => E5: 8
* PRF # F5: 3,4 => SOL
* DIS # H6: 5,7 => CTR => H6: 9
* PRF # H6: 9 => SOL
* DIS # G7: 1 => CTR => G7: 2,5
* DIS # G7: 5 => CTR => G7: 1,2
* DIS # I2: 3,6 => CTR => I2: 1,7
* CNT  15 HDP CHAINS /  41 HYP OPENED

--------------------------------------------------
* PREPARE PR GRAPH
* PAIR REDUCTION ..
* LEVEL 0 PASS 1 ROUND 1 (AUTO SOLVE) (A1,A5,A6,B6,C3,C5,C6,D2,D3,E6,E7,F3,F7,G6,H7,H8,H9,I7,I8,I9)
* ..856...95....2...2......4578615.....2.7...1....2.6..84936.....652391...8174259..
* PAIR A1: 1,3 ROW 1
G1: 1,3,2,7                              # reduction candidate for 1,3
G1: 2,7 => CTR
* 1.8564..95....2...2.98...4578615....32.7.9.1.941236..84936.8...652391...8174259..
* PAIR RESTART
* PAIR C3: 1,9 BLK 1
C2: 1,9,4                                # reduction candidate for 1,9
C2: 1,9 => SOLVED
* 378564129541932687269817345786159432924783516135246798493678251652391874817425963
* DURATION: 0:00:03.205375  START: 04:30:30.900278  END: 04:30:34.105653 2019-05-01
* SOLUTION FOUND
* SAVE PR GRAPH zz-www.sudokuoftheday.co.uk-20190313-absurd-base-pr-001.dot
* REASONING
* DIS # G1: 2,7 => CTR => G1: 1,3
* PRF G1: 1,3 # C2: 1,9 => SOL
* STA G1: 1,3 + C2: 1,9
* CNT   2 HDP CHAINS /   3 HYP OPENED

Header Info

http://www.sudokuoftheday.co.uk/cgi-bin/sudoku1280.cgi?ACTION=archive2&USER=&MONTH=Mar&YEAR=2019, 20190313, absurd

Solution

position: 378564129541932687269817345786159432924783516135246798493678251652391874817425963 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 # G1: 1,3 => UNS
* DIS # G1: 2,7 => CTR => G1: 1,3
* PRF # C2: 1,9 => SOL
* DIS # C2: 4 => CTR => C2: 1,9
* DIS # F1: 3,7 => CTR => F1: 4
* INC # F1: 4 => UNS
* INC # E2: 3,7 => UNS
* INC # E3: 3,7 => UNS
* INC # B3: 3,7 => UNS
* INC # G3: 3,7 => UNS
* INC # F5: 3,9 => UNS
* DIS # F5: 4,8 => CTR => F5: 3,9
* INC # G5: 4,5 => UNS
* DIS # G5: 3,6 => CTR => G5: 4,5
* INC # B1: 3,4 => UNS
* INC # B2: 3,4 => UNS
* DIS # F4: 3,4 => CTR => F4: 9
* PRF # F4: 9 => SOL
* DIS # E5: 3,4 => CTR => E5: 8
* INC # E5: 8 => UNS
* PRF # F5: 3,4 => SOL
* INC # F5: 8,9 => UNS
* INC # E2: 3,4 => UNS
* INC # E2: 1,7 => UNS
* DIS # H6: 5,7 => CTR => H6: 9
* PRF # H6: 9 => SOL
* INC # G7: 2,5 => UNS
* DIS # G7: 1 => CTR => G7: 2,5
* INC # G7: 1,2 => UNS
* DIS # G7: 5 => CTR => G7: 1,2
* INC # G8: 7,8 => UNS
* INC # G8: 4 => UNS
* INC # H2: 7,8 => UNS
* INC # H2: 3,6 => UNS
* INC # G8: 4,7 => UNS
* INC # G8: 8 => UNS
* INC # H2: 3,6 => UNS
* INC # H2: 7,8 => UNS
* DIS # I2: 3,6 => CTR => I2: 1,7
* INC # I2: 1,7 => UNS
* INC # I5: 3,6 => UNS
* CNT  41 HDP CHAINS /  41 HYP OPENED

A2. Pair Reduction

Full list of HDP chains traversed:

* INC # G1: 1,3 => UNS
* DIS # G1: 2,7 => CTR => G1: 1,3
* PRF G1: 1,3 # C2: 1,9 => SOL
* STA G1: 1,3 + C2: 1,9
* CNT   3 HDP CHAINS /   3 HYP OPENED