Analysis of zz-www.sudokuoftheday.co.uk-20190316-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: 3.5....16..7.....9....854..8....3....1....73.9..5.......2..41..4....8.......9.26. initial

Autosolve

position: 3459..816.87..6..9....854..8....3....1.8.973.9.35..6....2..41..4....8.....8.9.264 autosolve
Autosolve

Pair Reduction Variants

Pair Reduction Analysis

Pair Reduction Analysis

The following important HDP chains were detected:

* PRF # A3: 1,2 => SOL
* DIS # E6: 2,7 => CTR => E6: 1,4
* DIS # D2: 1,3 => CTR => D2: 4
* DIS # D8: 1,3 => CTR => D8: 2,6,7
* DIS # G8: 9 => CTR => G8: 3,5
* DIS # I3: 2,7 => CTR => I3: 3
* PRF # B4: 7 => SOL
* PRF # B4: 2,7 => SOL
* DIS # B4: 5 => CTR => B4: 2,7
* DIS # E6: 2,7 => CTR => E6: 1,4
* DIS # H4: 5,9 => CTR => H4: 2,4
* DIS # G8: 5,9 => CTR => G8: 3
* DIS # E7: 6,7 => CTR => E7: 3,5
* DIS # D8: 1,7 => CTR => D8: 2,3,6
* DIS # E8: 1,7 => CTR => E8: 2,3,5,6
* DIS # D9: 1,7 => CTR => D9: 3
* PRF # D9: 3 => SOL
* PRF # A9: 1,7 => SOL
* DIS # A9: 5 => CTR => A9: 1,7
* CNT  19 HDP CHAINS /  50 HYP OPENED

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

Pair Reduction

Pair Reduction

The following important HDP chains were detected:

* PRF # A3: 1,2 => SOL
* STA A3: 1,2
* CNT   1 HDP CHAINS /   1 HYP OPENED

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

Details

Positions

3.5....16..7.....9....854..8....3....1....73.9..5.......2..41..4....8.......9.26. initial
3459..816.87..6..9....854..8....3....1.8.973.9.35..6....2..41..4....8.....8.9.264 autosolve
345972816187436529269185473876213945514869732923547681632754198491628357758391264 solved

Classification

level: medium

Pairing Analysis

--------------------------------------------------
* PAIRS (19)
A2: 1,2
C3: 1,9
E1: 2,7
F1: 2,7
D3: 1,3
G2: 3,5
H2: 2,5
H3: 2,7
C4: 4,6
A5: 2,5
C5: 4,6
B6: 2,7
E5: 4,6
G4: 5,9
I5: 2,5
A7: 6,7
C8: 1,9
B9: 3,5
F9: 1,7

--------------------------------------------------
* CONSTRAINT PAIRS (AUTO SOLVE)
I4,I6: 1.. / I4 = 1  => 20 pairs (_) / I6 = 1  => 22 pairs (_)
C8,A9: 1.. / C8 = 1  => 19 pairs (_) / A9 = 1  =>  0 pairs (X)
C3,C8: 1.. / C3 = 1  =>  0 pairs (X) / C8 = 1  => 19 pairs (_)
F6,F9: 1.. / F6 = 1  => 23 pairs (_) / F9 = 1  => 23 pairs (_)
E1,F1: 2.. / E1 = 2  => 20 pairs (_) / F1 = 2  => 18 pairs (_)
D8,E8: 2.. / D8 = 2  => 19 pairs (_) / E8 = 2  =>  0 pairs (*)
A2,H2: 2.. / A2 = 2  =>  0 pairs (X) / H2 = 2  => 24 pairs (_)
A5,I5: 2.. / A5 = 2  =>  0 pairs (X) / I5 = 2  =>  0 pairs (_)
D4,D8: 2.. / D4 = 2  =>  0 pairs (*) / D8 = 2  =>  0 pairs (X)
F1,F6: 2.. / F1 = 2  => 18 pairs (_) / F6 = 2  => 20 pairs (_)
G2,I3: 3.. / G2 = 3  =>  0 pairs (X) / I3 = 3  => 24 pairs (_)
D3,I3: 3.. / D3 = 3  =>  0 pairs (X) / I3 = 3  => 24 pairs (_)
B9,D9: 3.. / B9 = 3  =>  0 pairs (X) / D9 = 3  =>  0 pairs (_)
G2,G8: 3.. / G2 = 3  =>  0 pairs (X) / G8 = 3  => 24 pairs (_)
D2,E2: 4.. / D2 = 4  => 20 pairs (_) / E2 = 4  =>  0 pairs (X)
C4,C5: 4.. / C4 = 4  => 18 pairs (_) / C5 = 4  => 16 pairs (_)
H4,H6: 4.. / H4 = 4  => 19 pairs (_) / H6 = 4  => 20 pairs (_)
C5,E5: 4.. / C5 = 4  => 16 pairs (_) / E5 = 4  => 18 pairs (_)
E6,H6: 4.. / E6 = 4  => 19 pairs (_) / H6 = 4  => 20 pairs (_)
D2,D4: 4.. / D2 = 4  => 20 pairs (_) / D4 = 4  =>  0 pairs (X)
G2,H2: 5.. / G2 = 5  => 24 pairs (_) / H2 = 5  =>  0 pairs (X)
B4,A5: 5.. / B4 = 5  =>  0 pairs (X) / A5 = 5  =>  0 pairs (_)
A9,B9: 5.. / A9 = 5  =>  0 pairs (X) / B9 = 5  =>  0 pairs (_)
E7,E8: 5.. / E7 = 5  => 19 pairs (_) / E8 = 5  =>  0 pairs (X)
A5,I5: 5.. / A5 = 5  =>  0 pairs (*) / I5 = 5  =>  0 pairs (X)
A5,A9: 5.. / A5 = 5  =>  0 pairs (*) / A9 = 5  =>  0 pairs (X)
B4,B9: 5.. / B4 = 5  =>  0 pairs (X) / B9 = 5  =>  0 pairs (_)
A3,B3: 6.. / A3 = 6  => 21 pairs (_) / B3 = 6  =>  0 pairs (*)
C4,C5: 6.. / C4 = 6  => 16 pairs (_) / C5 = 6  => 18 pairs (_)
C5,E5: 6.. / C5 = 6  => 18 pairs (_) / E5 = 6  => 16 pairs (_)
A3,A7: 6.. / A3 = 6  => 21 pairs (_) / A7 = 6  =>  0 pairs (*)
E1,F1: 7.. / E1 = 7  => 18 pairs (_) / F1 = 7  => 20 pairs (_)
H3,I3: 7.. / H3 = 7  => 20 pairs (_) / I3 = 7  =>  0 pairs (X)
B4,B6: 7.. / B4 = 7  =>  0 pairs (*) / B6 = 7  =>  0 pairs (X)
A7,A9: 7.. / A7 = 7  => 21 pairs (_) / A9 = 7  =>  0 pairs (*)
H6,I6: 8.. / H6 = 8  => 21 pairs (_) / I6 = 8  => 21 pairs (_)
H7,I7: 8.. / H7 = 8  => 21 pairs (_) / I7 = 8  => 21 pairs (_)
H6,H7: 8.. / H6 = 8  => 21 pairs (_) / H7 = 8  => 21 pairs (_)
I6,I7: 8.. / I6 = 8  => 21 pairs (_) / I7 = 8  => 21 pairs (_)
B3,C3: 9.. / B3 = 9  =>  0 pairs (X) / C3 = 9  => 19 pairs (_)
G4,H4: 9.. / G4 = 9  => 19 pairs (_) / H4 = 9  =>  0 pairs (X)
B7,H7: 9.. / B7 = 9  => 20 pairs (_) / H7 = 9  =>  0 pairs (*)
C3,C8: 9.. / C3 = 9  => 19 pairs (_) / C8 = 9  =>  0 pairs (X)
G4,G8: 9.. / G4 = 9  => 19 pairs (_) / G8 = 9  =>  0 pairs (X)
* DURATION: 0:00:54.672916  START: 04:34:02.205980  END: 04:34:56.878896 2019-05-01
* CP COUNT: (44)
* SOLUTION FOUND

--------------------------------------------------
* PREPARE PR GRAPH
* PAIR REDUCTION ..
* LEVEL 0 PASS 1 ROUND 1 (AUTO SOLVE) (A2,A5,A7,B6,B9,C3,C4,C5,C8,D3,E1,E5,F1,F9,G2,G4,H2,H3,I5)
* 3459..816.87..6..9....854..8....3....1.8.973.9.35..6....2..41..4....8.....8.9.264
* PAIR A2: 1,2 BLK 1
A3: 1,2,6                                # reduction candidate for 1,2
A3: 1,2 => SOLVED
* 345972816187436529269185473876213945514869732923547681632754198491628357758391264
A3: 6                                    # 21 pairs
* PAIR E1: 2,7 COL E
E4: 2,7,1,4,6                            # reduction candidate for 2,7
E4: 2,7                                  # 21 pairs
E6: 2,7,1,4                              # reduction candidate for 2,7
E6: 2,7 => CTR
* 345972816.87.16..91693854..8..7.3..1.1.8.973.973521648.92..418.4.1..8.....8197264
E6: 1,4                                  # 20 pairs
E8: 2,7,1,3,5,6                          # reduction candidate for 2,7
E8: 2,7                                  # 26 pairs
* PAIR F1: 2,7 COL F
F6: 2,7,1                                # reduction candidate for 2,7
F6: 2,7                                  # 23 pairs
F6: 1                                    # 23 pairs
* PAIR D3: 1,3 BLK 2
D2: 1,3,4                                # reduction candidate for 1,3
D2: 1,3 => CTR
* 3459..816.87.46..96291854738564739.1.1486973.9.35..648.926.418.4612.8....38791264
D2: 4                                    # 20 pairs
E2: 1,3,4                                # reduction candidate for 1,3
E2: 1,3                                  # 20 pairs
* PAIR D3: 1,3 COL D
D8: 1,3,2,6,7                            # reduction candidate for 1,3
D8: 1,3 => CTR
* 345972816.874.6..96..1854.387.2.3...51.8.973.9.35..6....26.41..46..28.....8791264
D8: 2,6,7                                # 19 pairs
D9: 1,3,7                                # reduction candidate for 1,3
D9: 1,3                                  # 25 pairs
* PAIR G2: 3,5 COL G
G8: 3,5,9                                # reduction candidate for 3,5
G8: 9 => CTR
* 3459..816.87..6359...3854..8....359.51.8.97329.35..648.92..41..4....8.....8.9.264
G8: 3,5                                  # 19 pairs
* PAIR H2: 2,5 COL H
H4: 2,5,4,9                              # reduction candidate for 2,5
H4: 2,5                                  # 21 pairs
H4: 4,9                                  # 20 pairs
* PAIR H3: 2,7 BLK 3
I3: 2,7,3                                # reduction candidate for 2,7
I3: 2,7 => CTR
* 3459..816287..6359...3854..85...3....1.8.973.9.35..6....2..41..4....8....38.9.264
I3: 3                                    # 24 pairs
* PAIR C4: 4,6 ROW 4
D4: 4,6,1,2,7                            # reduction candidate for 4,6
D4: 4,6                                  # 25 pairs
E4: 4,6,1,2,7                            # reduction candidate for 4,6
E4: 4,6                                  # 23 pairs
* PAIR A5: 2,5 BLK 4
B4: 2,5,7                                # reduction candidate for 2,5
B4: 7 => SOLVED
* 345972816187436529269185473876213945514869732923547681632754198491628357758391264
B4: 2,5                                  # 20 pairs
* PAIR B6: 2,7 BLK 4
B4: 2,7,5                                # reduction candidate for 2,7
B4: 2,7 => SOLVED
* 345972816187436529269185473876213945514869732923547681632754198491628357758391264
B4: 5 => CTR
* 3459..816187..6.2962918547385...394.21486973597354.68.7.2..41.84.1..83.7538791264
* PAIR B6: 2,7 ROW 6
E6: 2,7,1,4                              # reduction candidate for 2,7
E6: 2,7 => CTR
* 345972816.87.16..91693854..8..7.3..1.1.8.973.973521648.92..418.4.1..8.....8197264
E6: 1,4                                  # 20 pairs
F6: 2,7,1                                # reduction candidate for 2,7
F6: 2,7                                  # 23 pairs
* PAIR E5: 4,6 BLK 5
D4: 4,6,1,2,7                            # reduction candidate for 4,6
D4: 4,6                                  # 25 pairs
E4: 4,6,1,2,7                            # reduction candidate for 4,6
E4: 4,6                                  # 23 pairs
* PAIR G4: 5,9 BLK 6
H4: 5,9,2,4                              # reduction candidate for 5,9
H4: 5,9 => CTR
* 3459..816.87.365292691854738....395151.8.97329.351.64869275418.4.1..8...758391264
H4: 2,4                                  # 21 pairs
* PAIR G4: 5,9 COL G
G8: 5,9,3                                # reduction candidate for 5,9
G8: 5,9 => CTR
* 3459..816287..6359...3854..85...3....1.8.973.9.35..6....2..41..4....8....38.9.264
G8: 3                                    # 24 pairs
* PAIR I5: 2,5 BLK 6
H4: 2,5,4,9                              # reduction candidate for 2,5
H4: 2,5                                  # 21 pairs
I4: 2,5,1                                # reduction candidate for 2,5
I4: 2,5                                  # 22 pairs
* PAIR A7: 6,7 ROW 7
D7: 6,7,3                                # reduction candidate for 6,7
D7: 6,7                                  # 22 pairs
E7: 6,7,3,5                              # reduction candidate for 6,7
E7: 6,7 => CTR
* 3459..81618743652962918547385.67394..1.8.973.9.35..6...923641..461258397.38791264
E7: 3,5                                  # 20 pairs
* PAIR F9: 1,7 BLK 8
D8: 1,7,2,3,6                            # reduction candidate for 1,7
D8: 1,7 => CTR
* 345972816.874.6..96...854..87.2.3...51.8.97329235.76..7.26541..46..28...1.8.9.264
D8: 2,3,6                                # 19 pairs
E8: 1,7,2,3,5,6                          # reduction candidate for 1,7
E8: 1,7 => CTR
* 3459..816.87.36529...1854738....39...1.8.973.9.35..6....26541..4612783957.8.9.264
E8: 2,3,5,6                              # 19 pairs
D9: 1,7,3                                # reduction candidate for 1,7
D9: 1,7 => CTR
* 3459..816187..6.2962918547385...394.21486973597354.68.7.2..41.84.1..83.7538791264
D9: 3 => SOLVED
* 345972816187436529269185473876213945514869732923547681632754198491628357758391264
* PAIR F9: 1,7 ROW 9
A9: 1,7,5                                # reduction candidate for 1,7
A9: 1,7 => SOLVED
* 345972816187436529269185473876213945514869732923547681632754198491628357758391264
A9: 5 => CTR
* 3459.7816187..652962918547385..739412148697359735..6..7.2..41.84.1..83.7538791264
* PAIR F9: 1,7 COL F
F6: 1,7,2                                # reduction candidate for 1,7
F6: 2                                    # 20 pairs
F6: 1,7                                  # 18 pairs
* INCONCLUSIVE
* SAVE PR GRAPH zz-www.sudokuoftheday.co.uk-20190316-absurd-base-pr-000.dot
* REASONING
* PRF # A3: 1,2 => SOL
* DIS # E6: 2,7 => CTR => E6: 1,4
* DIS # D2: 1,3 => CTR => D2: 4
* DIS # D8: 1,3 => CTR => D8: 2,6,7
* DIS # G8: 9 => CTR => G8: 3,5
* DIS # I3: 2,7 => CTR => I3: 3
* PRF # B4: 7 => SOL
* PRF # B4: 2,7 => SOL
* DIS # B4: 5 => CTR => B4: 2,7
* DIS # E6: 2,7 => CTR => E6: 1,4
* DIS # H4: 5,9 => CTR => H4: 2,4
* DIS # G8: 5,9 => CTR => G8: 3
* DIS # E7: 6,7 => CTR => E7: 3,5
* DIS # D8: 1,7 => CTR => D8: 2,3,6
* DIS # E8: 1,7 => CTR => E8: 2,3,5,6
* DIS # D9: 1,7 => CTR => D9: 3
* PRF # D9: 3 => SOL
* PRF # A9: 1,7 => SOL
* DIS # A9: 5 => CTR => A9: 1,7
* CNT  19 HDP CHAINS /  50 HYP OPENED

--------------------------------------------------
* PREPARE PR GRAPH
* PAIR REDUCTION ..
* LEVEL 0 PASS 1 ROUND 1 (AUTO SOLVE) (A2,A5,A7,B6,B9,C3,C4,C5,C8,D3,E1,E5,F1,F9,G2,G4,H2,H3,I5)
* 3459..816.87..6..9....854..8....3....1.8.973.9.35..6....2..41..4....8.....8.9.264
* PAIR A2: 1,2 BLK 1
A3: 1,2,6                                # reduction candidate for 1,2
A3: 1,2 => SOLVED
* 345972816187436529269185473876213945514869732923547681632754198491628357758391264
* DURATION: 0:00:02.034185  START: 04:35:30.933095  END: 04:35:32.967280 2019-05-01
* SOLUTION FOUND
* SAVE PR GRAPH zz-www.sudokuoftheday.co.uk-20190316-absurd-base-pr-001.dot
* REASONING
* PRF # A3: 1,2 => SOL
* STA A3: 1,2
* CNT   1 HDP CHAINS /   1 HYP OPENED

Header Info

http://www.sudokuoftheday.co.uk/cgi-bin/sudoku1280.cgi?ACTION=archive2&USER=&MONTH=Mar&YEAR=2019, 20190316, absurd

Solution

position: 345972816187436529269185473876213945514869732923547681632754198491628357758391264 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:

* PRF # A3: 1,2 => SOL
* INC # A3: 6 => UNS
* INC # E4: 2,7 => UNS
* DIS # E6: 2,7 => CTR => E6: 1,4
* INC # E6: 1,4 => UNS
* INC # E8: 2,7 => UNS
* INC # F6: 2,7 => UNS
* INC # F6: 1 => UNS
* DIS # D2: 1,3 => CTR => D2: 4
* INC # D2: 4 => UNS
* INC # E2: 1,3 => UNS
* DIS # D8: 1,3 => CTR => D8: 2,6,7
* INC # D8: 2,6,7 => UNS
* INC # D9: 1,3 => UNS
* INC # G8: 3,5 => UNS
* DIS # G8: 9 => CTR => G8: 3,5
* INC # H4: 2,5 => UNS
* INC # H4: 4,9 => UNS
* DIS # I3: 2,7 => CTR => I3: 3
* INC # I3: 3 => UNS
* INC # D4: 4,6 => UNS
* INC # E4: 4,6 => UNS
* INC # B4: 2,5 => UNS
* PRF # B4: 7 => SOL
* PRF # B4: 2,7 => SOL
* DIS # B4: 5 => CTR => B4: 2,7
* DIS # E6: 2,7 => CTR => E6: 1,4
* INC # E6: 1,4 => UNS
* INC # F6: 2,7 => UNS
* INC # D4: 4,6 => UNS
* INC # E4: 4,6 => UNS
* DIS # H4: 5,9 => CTR => H4: 2,4
* INC # H4: 2,4 => UNS
* DIS # G8: 5,9 => CTR => G8: 3
* INC # G8: 3 => UNS
* INC # H4: 2,5 => UNS
* INC # I4: 2,5 => UNS
* INC # D7: 6,7 => UNS
* DIS # E7: 6,7 => CTR => E7: 3,5
* INC # E7: 3,5 => UNS
* DIS # D8: 1,7 => CTR => D8: 2,3,6
* INC # D8: 2,3,6 => UNS
* DIS # E8: 1,7 => CTR => E8: 2,3,5,6
* INC # E8: 2,3,5,6 => UNS
* DIS # D9: 1,7 => CTR => D9: 3
* PRF # D9: 3 => SOL
* PRF # A9: 1,7 => SOL
* DIS # A9: 5 => CTR => A9: 1,7
* INC # F6: 1,7 => UNS
* INC # F6: 2 => UNS
* CNT  50 HDP CHAINS /  50 HYP OPENED

A2. Pair Reduction

Full list of HDP chains traversed:

* PRF # A3: 1,2 => SOL
* STA A3: 1,2
* CNT   1 HDP CHAINS /   1 HYP OPENED