Analysis of zz-www.sudokuoftheday.co.uk-20060829-absurd-base.sdk

Contents

Sudoku from http://www.sudokuoftheday.co.uk/cgi-bin/sudoku1280.cgi?ACTION=archive2&USER=&MONTH=Aug&YEAR=2006

level: medium

Sudoku from http://www.sudokuoftheday.co.uk/cgi-bin/sudoku1280.cgi?ACTION=archive2&USER=&MONTH=Aug&YEAR=2006

position: ....6.......5.3.42......38..2..86..56...2..3..5....2...7..9....4..61...3..1..2674 initial

Autosolve

position: ....68....6.573.42...24.386.2..86..56...25.3..5..3.26..76394...48.617..3..1852674 autosolve
Autosolve

Pair Reduction Variants

Pair Reduction Analysis

Pair Reduction Analysis

The following important HDP chains were detected:

* DIS # C1: 4 => CTR => C1: 2,3
* DIS # C1: 2 => CTR => C1: 3,4
* DIS # A2: 8,9 => CTR => A2: 1
* PRF # A2: 1 => SOL
* DIS # A2: 8 => CTR => A2: 1,9
* DIS # B5: 4 => CTR => B5: 1,9
* DIS # H1: 1,9 => CTR => H1: 5
* DIS # H1: 1,9 => CTR => H1: 5
* DIS # A2: 8 => CTR => A2: 1,9
* DIS # G4: 1,9 => CTR => G4: 4,7
* DIS # G5: 1,9 => CTR => G5: 4,7,8
* DIS # A6: 1,9 => CTR => A6: 7,8
* DIS # G4: 1,9 => CTR => G4: 4,7
* DIS # G5: 1,9 => CTR => G5: 4,7,8
* DIS # H1: 1,9 => CTR => H1: 5
* DIS # H7: 1 => CTR => H7: 2,5
* DIS # H8: 2,5 => CTR => H8: 9
* DIS # G7: 5 => CTR => G7: 1,8
* DIS # H8: 2 => CTR => H8: 5,9
* DIS # G1: 5,9 => CTR => G1: 1,7
* CNT  20 HDP CHAINS /  59 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 # C1: 4 => CTR => C1: 2,3
* DIS C1: 2,3 # H1: 1,9 => CTR => H1: 5
* DIS C1: 2,3 + H1: 5 # G4: 1,9 => CTR => G4: 4,7
* DIS C1: 2,3 + H1: 5 + G4: 4,7 # G5: 1,9 => CTR => G5: 4,7,8
* DIS C1: 2,3 + H1: 5 + G4: 4,7 + G5: 4,7,8 # G7: 5 => CTR => G7: 1,8
* DIS C1: 2,3 + H1: 5 + G4: 4,7 + G5: 4,7,8 + G7: 1,8 # C5: 8,9 => CTR => C5: 4,7
* DIS C1: 2,3 + H1: 5 + G4: 4,7 + G5: 4,7,8 + G7: 1,8 + C5: 4,7 # C6: 8,9 => CTR => C6: 4,7
* PRF C1: 2,3 + H1: 5 + G4: 4,7 + G5: 4,7,8 + G7: 1,8 + C5: 4,7 + C6: 4,7 => SOL
* STA C1: 2,3 + H1: 5 + G4: 4,7 + G5: 4,7,8 + G7: 1,8 + C5: 4,7 + C6: 4,7
* CNT   8 HDP CHAINS /  34 HYP OPENED

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

Details

Positions

....6.......5.3.42......38..2..86..56...2..3..5....2...7..9....4..61...3..1..2674 initial
....68....6.573.42...24.386.2..86..56...25.3..5..3.26..76394...48.617..3..1852674 autosolve
243968751168573942795241386329786415617425839854139267576394128482617593931852674 solved

Classification

level: medium

Pairing Analysis

--------------------------------------------------
* PAIRS (17)
A1: 2,3
B1: 3,4
C2: 8,9
A3: 5,7
B3: 1,9
C3: 5,7
D1: 1,9
F3: 1,9
G2: 1,9
F6: 1,9
H4: 1,9
A7: 2,5
C8: 2,5
A9: 3,9
B9: 3,9
I7: 1,8
G8: 5,9

--------------------------------------------------
* CONSTRAINT PAIRS (AUTO SOLVE)
A2,B3: 1.. / A2 = 1  =>  0 pairs (*) / B3 = 1  =>  0 pairs (X)
D1,F3: 1.. / D1 = 1  =>  0 pairs (X) / F3 = 1  =>  0 pairs (_)
A2,G2: 1.. / A2 = 1  =>  0 pairs (*) / G2 = 1  =>  0 pairs (X)
B3,F3: 1.. / B3 = 1  =>  0 pairs (X) / F3 = 1  =>  0 pairs (_)
B3,B5: 1.. / B3 = 1  =>  0 pairs (X) / B5 = 1  =>  0 pairs (_)
F3,F6: 1.. / F3 = 1  =>  0 pairs (*) / F6 = 1  =>  0 pairs (X)
A1,C1: 2.. / A1 = 2  => 15 pairs (_) / C1 = 2  =>  0 pairs (X)
A7,C8: 2.. / A7 = 2  =>  0 pairs (X) / C8 = 2  => 15 pairs (_)
H7,H8: 2.. / H7 = 2  => 15 pairs (_) / H8 = 2  =>  0 pairs (X)
A7,H7: 2.. / A7 = 2  =>  0 pairs (X) / H7 = 2  => 15 pairs (_)
C8,H8: 2.. / C8 = 2  => 15 pairs (_) / H8 = 2  =>  0 pairs (X)
A1,A7: 2.. / A1 = 2  => 15 pairs (_) / A7 = 2  =>  0 pairs (X)
C1,C8: 2.. / C1 = 2  =>  0 pairs (X) / C8 = 2  => 15 pairs (_)
A4,C4: 3.. / A4 = 3  => 14 pairs (_) / C4 = 3  => 18 pairs (_)
A9,B9: 3.. / A9 = 3  =>  0 pairs (X) / B9 = 3  => 17 pairs (_)
B1,B9: 3.. / B1 = 3  =>  0 pairs (X) / B9 = 3  => 17 pairs (_)
C1,C4: 3.. / C1 = 3  => 14 pairs (_) / C4 = 3  => 18 pairs (_)
B1,C1: 4.. / B1 = 4  => 17 pairs (_) / C1 = 4  =>  0 pairs (X)
G4,G5: 4.. / G4 = 4  => 17 pairs (_) / G5 = 4  => 20 pairs (_)
C6,D6: 4.. / C6 = 4  => 17 pairs (_) / D6 = 4  => 17 pairs (_)
B1,B5: 4.. / B1 = 4  => 17 pairs (_) / B5 = 4  =>  0 pairs (X)
A3,C3: 5.. / A3 = 5  =>  0 pairs (X) / C3 = 5  => 15 pairs (_)
G1,H1: 5.. / G1 = 5  =>  0 pairs (X) / H1 = 5  => 19 pairs (_)
A7,C8: 5.. / A7 = 5  => 15 pairs (_) / C8 = 5  =>  0 pairs (X)
A3,A7: 5.. / A3 = 5  =>  0 pairs (X) / A7 = 5  => 15 pairs (_)
C3,C8: 5.. / C3 = 5  => 15 pairs (_) / C8 = 5  =>  0 pairs (X)
A3,C3: 7.. / A3 = 7  => 15 pairs (_) / C3 = 7  =>  0 pairs (X)
G1,I1: 7.. / G1 = 7  => 20 pairs (_) / I1 = 7  => 25 pairs (_)
A2,C2: 8.. / A2 = 8  =>  0 pairs (X) / C2 = 8  => 18 pairs (_)
G7,I7: 8.. / G7 = 8  => 18 pairs (_) / I7 = 8  => 20 pairs (_)
A2,A6: 8.. / A2 = 8  =>  0 pairs (X) / A6 = 8  => 18 pairs (_)
G5,G7: 8.. / G5 = 8  => 20 pairs (_) / G7 = 8  => 18 pairs (_)
D1,F3: 9.. / D1 = 9  =>  0 pairs (*) / F3 = 9  =>  0 pairs (X)
A9,B9: 9.. / A9 = 9  => 17 pairs (_) / B9 = 9  =>  0 pairs (X)
G8,H8: 9.. / G8 = 9  =>  0 pairs (X) / H8 = 9  => 15 pairs (_)
B3,F3: 9.. / B3 = 9  =>  0 pairs (*) / F3 = 9  =>  0 pairs (X)
F3,F6: 9.. / F3 = 9  =>  0 pairs (X) / F6 = 9  =>  0 pairs (_)
* DURATION: 0:00:56.450416  START: 02:10:17.574860  END: 02:11:14.025276 2019-05-01
* CP COUNT: (37)
* SOLUTION FOUND

--------------------------------------------------
* PREPARE PR GRAPH
* PAIR REDUCTION ..
* LEVEL 0 PASS 1 ROUND 1 (AUTO SOLVE) (A1,A3,A7,A9,B1,B3,B9,C2,C3,C8,D1,F3,F6,G2,G8,H4,I7)
* ....68....6.573.42...24.386.2..86..56...25.3..5..3.26..76394...48.617..3..1852674
* PAIR A1: 2,3 BLK 1
C1: 2,3,4                                # reduction candidate for 2,3
C1: 4 => CTR
* 234168....6.57314271524938612378649564.925.31.5.43126.57639482.482617..3391852674
C1: 2,3                                  # 17 pairs
* PAIR B1: 3,4 BLK 1
C1: 3,4,2                                # reduction candidate for 3,4
C1: 2 => CTR
* 342168...869573142517249386123.86.9569..25.3175.931268276394...485617923931852674
C1: 3,4                                  # 15 pairs
* PAIR C2: 8,9 BLK 1
A2: 8,9,1                                # reduction candidate for 8,9
A2: 8,9 => CTR
* ..2168.59.6.573142.1.249386123.86.956...25831.5..31267276394518485617923..1852674
A2: 1 => SOLVED
* 243968751168573942795241386329786415617425839854139267576394128482617593931852674
* PAIR C2: 8,9 COL C
C5: 8,9,4,7                              # reduction candidate for 8,9
C5: 8,9                                  # 19 pairs
C6: 8,9,4,7                              # reduction candidate for 8,9
C6: 8,9                                  # 19 pairs
* PAIR B3: 1,9 BLK 1
A2: 1,9,8                                # reduction candidate for 1,9
A2: 8 => CTR
* ..2168.59869573142.1.249386123.86.956...25831.58431267276394518485617923..1852674
A2: 1,9                                  # 18 pairs
* PAIR B3: 1,9 COL B
B5: 1,9,4                                # reduction candidate for 1,9
B5: 4 => CTR
* .34168....6.573142.1.249386123.8649564.925.31.5.43126..76394.18482617953.91852674
B5: 1,9                                  # 17 pairs
* PAIR D1: 1,9 ROW 1
G1: 1,9,5,7                              # reduction candidate for 1,9
G1: 1,9                                  # 20 pairs
H1: 1,9,5                                # reduction candidate for 1,9
H1: 1,9 => CTR
* ....68597.6.573142.1.249386.2..86.156..125.3..5..3.26..76394...48.6179.3..1852674
H1: 5                                    # 19 pairs
I1: 1,9,7                                # reduction candidate for 1,9
I1: 1,9                                  # 20 pairs
* PAIR D1: 1,9 COL D
D4: 1,9,4,7                              # reduction candidate for 1,9
D4: 1,9                                  # 23 pairs
D5: 1,9,4,7                              # reduction candidate for 1,9
D5: 1,9                                  # 20 pairs
D6: 1,9,4,7                              # reduction candidate for 1,9
D6: 1,9                                  # 22 pairs
* PAIR G2: 1,9 BLK 3
G1: 1,9,5,7                              # reduction candidate for 1,9
G1: 1,9                                  # 20 pairs
H1: 1,9,5                                # reduction candidate for 1,9
H1: 1,9 => CTR
* ....68597.6.573142.1.249386.2..86.156..125.3..5..3.26..76394...48.6179.3..1852674
H1: 5                                    # 19 pairs
I1: 1,9,7                                # reduction candidate for 1,9
I1: 1,9                                  # 20 pairs
* PAIR G2: 1,9 ROW 2
A2: 1,9,8                                # reduction candidate for 1,9
A2: 8 => CTR
* ..2168.59869573142.1.249386123.86.956...25831.58431267276394518485617923..1852674
A2: 1,9                                  # 18 pairs
* PAIR G2: 1,9 COL G
G4: 1,9,4,7                              # reduction candidate for 1,9
G4: 1,9 => CTR
* .4..68759.6.573142.1.249386.2..8691569.12543..5..3.26..763948.148.617..3..1852674
G4: 4,7                                  # 18 pairs
G5: 1,9,4,7,8                            # reduction candidate for 1,9
G5: 1,9 => CTR
* ....68759.6.573142.1.249386.2..864156..125.3..5..3.26..763948.148.617..3..1852674
G5: 4,7,8                                # 17 pairs
* PAIR F6: 1,9 BLK 5
D4: 1,9,4,7                              # reduction candidate for 1,9
D4: 1,9                                  # 23 pairs
D5: 1,9,4,7                              # reduction candidate for 1,9
D5: 1,9                                  # 20 pairs
D6: 1,9,4,7                              # reduction candidate for 1,9
D6: 1,9                                  # 22 pairs
* PAIR F6: 1,9 ROW 6
A6: 1,9,7,8                              # reduction candidate for 1,9
A6: 1,9 => CTR
* 234168.59869573142715249386123.86.956...25.3195..3126..76394.1848.617923391852674
A6: 7,8                                  # 18 pairs
I6: 1,9,7,8                              # reduction candidate for 1,9
I6: 1,9                                  # 22 pairs
* PAIR H4: 1,9 BLK 6
G4: 1,9,4,7                              # reduction candidate for 1,9
G4: 1,9 => CTR
* .4..68759.6.573142.1.249386.2..8691569.12543..5..3.26..763948.148.617..3..1852674
G4: 4,7                                  # 18 pairs
G5: 1,9,4,7,8                            # reduction candidate for 1,9
G5: 1,9 => CTR
* ....68759.6.573142.1.249386.2..864156..125.3..5..3.26..763948.148.617..3..1852674
G5: 4,7,8                                # 17 pairs
I5: 1,9,7,8                              # reduction candidate for 1,9
I5: 1,9                                  # 20 pairs
I6: 1,9,7,8                              # reduction candidate for 1,9
I6: 1,9                                  # 22 pairs
* PAIR H4: 1,9 ROW 4
A4: 1,9,3,7                              # reduction candidate for 1,9
A4: 1,9                                  # 21 pairs
D4: 1,9,4,7                              # reduction candidate for 1,9
D4: 1,9                                  # 23 pairs
* PAIR H4: 1,9 COL H
H1: 1,9,5                                # reduction candidate for 1,9
H1: 1,9 => CTR
* ....68597.6.573142.1.249386.2..86.156..125.3..5..3.26..76394...48.6179.3..1852674
H1: 5                                    # 19 pairs
* PAIR A7: 2,5 ROW 7
H7: 2,5,1                                # reduction candidate for 2,5
H7: 1 => CTR
* 342.68.59.6.573142517249386.23.86.9569..2583..5.9312672763945184856179239.1852674
H7: 2,5                                  # 19 pairs
* PAIR C8: 2,5 ROW 8
H8: 2,5,9                                # reduction candidate for 2,5
H8: 2,5 => CTR
* ..2168.59.6.573142.1.249386123.86.956...25831.5..31267276394518485617923..1852674
H8: 9                                    # 15 pairs
* PAIR A9: 3,9 COL A
A4: 3,9,1,7                              # reduction candidate for 3,9
A4: 1,7                                  # 19 pairs
A4: 3,9                                  # 18 pairs
* PAIR I7: 1,8 BLK 9
G7: 1,8,5                                # reduction candidate for 1,8
G7: 5 => CTR
* ..2.68.59.6.573142517249386.23.864956...2583..5..312672763945.8485617923..1852674
G7: 1,8                                  # 19 pairs
* PAIR I7: 1,8 COL I
I5: 1,8,7,9                              # reduction candidate for 1,8
I5: 1,8                                  # 20 pairs
I6: 1,8,7,9                              # reduction candidate for 1,8
I6: 1,8                                  # 20 pairs
* PAIR G8: 5,9 BLK 9
H8: 5,9,2                                # reduction candidate for 5,9
H8: 2 => CTR
* 342168....6.573142517249386123.86.9569..25.3175.931268276394...485617923..1852674
H8: 5,9                                  # 15 pairs
* PAIR G8: 5,9 COL G
G1: 5,9,1,7                              # reduction candidate for 5,9
G1: 5,9 => CTR
* ...168..7.6.573142.1.249386.2..86.156...25.3.15..3.26..76394..148.617..3..1852674
G1: 1,7                                  # 20 pairs
* INCONCLUSIVE
* SAVE PR GRAPH zz-www.sudokuoftheday.co.uk-20060829-absurd-base-pr-000.dot
* REASONING
* DIS # C1: 4 => CTR => C1: 2,3
* DIS # C1: 2 => CTR => C1: 3,4
* DIS # A2: 8,9 => CTR => A2: 1
* PRF # A2: 1 => SOL
* DIS # A2: 8 => CTR => A2: 1,9
* DIS # B5: 4 => CTR => B5: 1,9
* DIS # H1: 1,9 => CTR => H1: 5
* DIS # H1: 1,9 => CTR => H1: 5
* DIS # A2: 8 => CTR => A2: 1,9
* DIS # G4: 1,9 => CTR => G4: 4,7
* DIS # G5: 1,9 => CTR => G5: 4,7,8
* DIS # A6: 1,9 => CTR => A6: 7,8
* DIS # G4: 1,9 => CTR => G4: 4,7
* DIS # G5: 1,9 => CTR => G5: 4,7,8
* DIS # H1: 1,9 => CTR => H1: 5
* DIS # H7: 1 => CTR => H7: 2,5
* DIS # H8: 2,5 => CTR => H8: 9
* DIS # G7: 5 => CTR => G7: 1,8
* DIS # H8: 2 => CTR => H8: 5,9
* DIS # G1: 5,9 => CTR => G1: 1,7
* CNT  20 HDP CHAINS /  59 HYP OPENED

--------------------------------------------------
* PREPARE PR GRAPH
* PAIR REDUCTION ..
* LEVEL 0 PASS 1 ROUND 1 (AUTO SOLVE) (A1,A3,A7,A9,B1,B3,B9,C2,C3,C8,D1,F3,F6,G2,G8,H4,I7)
* ....68....6.573.42...24.386.2..86..56...25.3..5..3.26..76394...48.617..3..1852674
* PAIR A1: 2,3 BLK 1
C1: 2,3,4                                # reduction candidate for 2,3
C1: 4 => CTR
* 234168....6.57314271524938612378649564.925.31.5.43126.57639482.482617..3391852674
* PAIR C2: 8,9 COL C
C5: 8,9,4,7                              # reduction candidate for 8,9
C5: 8,9                                  # 19 pairs
C6: 8,9,4,7                              # reduction candidate for 8,9
C6: 8,9                                  # 19 pairs
* PAIR D1: 1,9 ROW 1
G1: 1,9,5,7                              # reduction candidate for 1,9
G1: 1,9                                  # 16 pairs
H1: 1,9,5                                # reduction candidate for 1,9
H1: 1,9 => CTR
* .4..68597.69573142.1.249386.2.986.1569.125.3..5..3.26..76394...48.6179.3931852674
I1: 1,9,7                                # reduction candidate for 1,9
I1: 1,9                                  # 20 pairs
* PAIR D1: 1,9 COL D
D4: 1,9,4,7                              # reduction candidate for 1,9
D4: 1,9                                  # 25 pairs
D5: 1,9,4,7                              # reduction candidate for 1,9
D5: 1,9                                  # 23 pairs
D6: 1,9,4,7                              # reduction candidate for 1,9
D6: 1,9                                  # 24 pairs
* PAIR RESTART
* PAIR D1: 1,9 ROW 1
G1: 1,9,7                                # reduction candidate for 1,9
G1: 1,9                                  # 16 pairs
I1: 1,9,7                                # reduction candidate for 1,9
I1: 1,9                                  # 20 pairs
* PAIR D1: 1,9 COL D
D4: 1,9,4,7                              # reduction candidate for 1,9
D4: 1,9                                  # 25 pairs
D5: 1,9,4,7                              # reduction candidate for 1,9
D5: 1,9                                  # 23 pairs
D6: 1,9,4,7                              # reduction candidate for 1,9
D6: 1,9                                  # 24 pairs
* PAIR G2: 1,9 BLK 3
G1: 1,9,7                                # reduction candidate for 1,9
G1: 1,9                                  # 16 pairs
I1: 1,9,7                                # reduction candidate for 1,9
I1: 1,9                                  # 20 pairs
* PAIR G2: 1,9 COL G
G4: 1,9,4,7                              # reduction candidate for 1,9
G4: 1,9 => CTR
* .4..68759.69573142.15249386.2..8691569.12543..5..3.26..763948.148.617593931852674
G5: 1,9,4,7,8                            # reduction candidate for 1,9
G5: 1,9 => CTR
* .4..68759.69573142.15249386.2.98641569..25.3..5..3.26..763948.148.617593931852674
* RESTART
* PAIR RESTART
* PAIR G2: 1,9 BLK 3
G1: 1,9,7                                # reduction candidate for 1,9
G1: 1,9                                  # 16 pairs
I1: 1,9,7                                # reduction candidate for 1,9
I1: 1,9                                  # 20 pairs
* PAIR F6: 1,9 BLK 5
D4: 1,9,4,7                              # reduction candidate for 1,9
D4: 1,9                                  # 25 pairs
D5: 1,9,4,7                              # reduction candidate for 1,9
D5: 1,9                                  # 29 pairs
D6: 1,9,4,7                              # reduction candidate for 1,9
D6: 1,9                                  # 29 pairs
* PAIR F6: 1,9 ROW 6
I6: 1,9,7,8                              # reduction candidate for 1,9
I6: 1,9                                  # 24 pairs
I6: 7,8                                  # 23 pairs
* PAIR H4: 1,9 BLK 6
I5: 1,9,7,8                              # reduction candidate for 1,9
I5: 1,9                                  # 23 pairs
I6: 1,9,7,8                              # reduction candidate for 1,9
I6: 1,9                                  # 24 pairs
* PAIR H4: 1,9 ROW 4
D4: 1,9,4,7                              # reduction candidate for 1,9
D4: 1,9                                  # 25 pairs
D4: 4,7                                  # 24 pairs
* PAIR I7: 1,8 BLK 9
G7: 1,8,5                                # reduction candidate for 1,8
G7: 5 => CTR
* .42.68.59.69573142517249386.23.86495694.2583..58.3.26..763945.8485617923931852674

* LEVEL 0 PASS 1 ROUND 2 (AUTO SOLVE) (A2,A6,B3,B5,C2,D1,F3,F6,G2,G4,G7,I1,I7)
* 243.68.5..6.573.427.524.38632..86.156...25.3..5..3.26.576394.2.482617593931852674
* PAIR C2: 8,9 COL C
C5: 8,9,4,7                              # reduction candidate for 8,9
C5: 8,9 => CTR
* 243168957.6957314271524.38632..86.156...25.3..5..3.26.576394.2.482617593931852674
C6: 8,9,4,7                              # reduction candidate for 8,9
C6: 8,9 => CTR
* 243.6875116857394279524138632..86.156...25.3..5.43.267576394.2.482617593931852674
C6: 4,7 => SOLVED
* 243968751168573942795241386329786415617425839854139267576394128482617593931852674
* DURATION: 0:00:28.480913  START: 02:11:58.948347  END: 02:12:27.429260 2019-05-01
* SOLUTION FOUND
* SAVE PR GRAPH zz-www.sudokuoftheday.co.uk-20060829-absurd-base-pr-001.dot
* REASONING
* DIS # C1: 4 => CTR => C1: 2,3
* DIS C1: 2,3 # H1: 1,9 => CTR => H1: 5
* DIS C1: 2,3 + H1: 5 # G4: 1,9 => CTR => G4: 4,7
* DIS C1: 2,3 + H1: 5 + G4: 4,7 # G5: 1,9 => CTR => G5: 4,7,8
* DIS C1: 2,3 + H1: 5 + G4: 4,7 + G5: 4,7,8 # G7: 5 => CTR => G7: 1,8
* DIS C1: 2,3 + H1: 5 + G4: 4,7 + G5: 4,7,8 + G7: 1,8 # C5: 8,9 => CTR => C5: 4,7
* DIS C1: 2,3 + H1: 5 + G4: 4,7 + G5: 4,7,8 + G7: 1,8 + C5: 4,7 # C6: 8,9 => CTR => C6: 4,7
* PRF C1: 2,3 + H1: 5 + G4: 4,7 + G5: 4,7,8 + G7: 1,8 + C5: 4,7 + C6: 4,7 => SOL
* STA C1: 2,3 + H1: 5 + G4: 4,7 + G5: 4,7,8 + G7: 1,8 + C5: 4,7 + C6: 4,7
* CNT   8 HDP CHAINS /  34 HYP OPENED

Header Info

http://www.sudokuoftheday.co.uk/cgi-bin/sudoku1280.cgi?ACTION=archive2&USER=&MONTH=Aug&YEAR=2006, 20060829, absurd

Solution

position: 243968751168573942795241386329786415617425839854139267576394128482617593931852674 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 # C1: 2,3 => UNS
* DIS # C1: 4 => CTR => C1: 2,3
* INC # C1: 3,4 => UNS
* DIS # C1: 2 => CTR => C1: 3,4
* DIS # A2: 8,9 => CTR => A2: 1
* PRF # A2: 1 => SOL
* INC # C5: 8,9 => UNS
* INC # C6: 8,9 => UNS
* INC # A2: 1,9 => UNS
* DIS # A2: 8 => CTR => A2: 1,9
* INC # B5: 1,9 => UNS
* DIS # B5: 4 => CTR => B5: 1,9
* INC # G1: 1,9 => UNS
* DIS # H1: 1,9 => CTR => H1: 5
* INC # H1: 5 => UNS
* INC # I1: 1,9 => UNS
* INC # D4: 1,9 => UNS
* INC # D5: 1,9 => UNS
* INC # D6: 1,9 => UNS
* INC # G1: 1,9 => UNS
* DIS # H1: 1,9 => CTR => H1: 5
* INC # H1: 5 => UNS
* INC # I1: 1,9 => UNS
* INC # A2: 1,9 => UNS
* DIS # A2: 8 => CTR => A2: 1,9
* DIS # G4: 1,9 => CTR => G4: 4,7
* INC # G4: 4,7 => UNS
* DIS # G5: 1,9 => CTR => G5: 4,7,8
* INC # G5: 4,7,8 => UNS
* INC # D4: 1,9 => UNS
* INC # D5: 1,9 => UNS
* INC # D6: 1,9 => UNS
* DIS # A6: 1,9 => CTR => A6: 7,8
* INC # A6: 7,8 => UNS
* INC # I6: 1,9 => UNS
* DIS # G4: 1,9 => CTR => G4: 4,7
* INC # G4: 4,7 => UNS
* DIS # G5: 1,9 => CTR => G5: 4,7,8
* INC # G5: 4,7,8 => UNS
* INC # I5: 1,9 => UNS
* INC # I6: 1,9 => UNS
* INC # A4: 1,9 => UNS
* INC # D4: 1,9 => UNS
* DIS # H1: 1,9 => CTR => H1: 5
* INC # H1: 5 => UNS
* INC # H7: 2,5 => UNS
* DIS # H7: 1 => CTR => H7: 2,5
* DIS # H8: 2,5 => CTR => H8: 9
* INC # H8: 9 => UNS
* INC # A4: 3,9 => UNS
* INC # A4: 1,7 => UNS
* INC # G7: 1,8 => UNS
* DIS # G7: 5 => CTR => G7: 1,8
* INC # I5: 1,8 => UNS
* INC # I6: 1,8 => UNS
* INC # H8: 5,9 => UNS
* DIS # H8: 2 => CTR => H8: 5,9
* DIS # G1: 5,9 => CTR => G1: 1,7
* INC # G1: 1,7 => UNS
* CNT  59 HDP CHAINS /  59 HYP OPENED

A2. Pair Reduction

Full list of HDP chains traversed:

* INC # C1: 2,3 => UNS
* DIS # C1: 4 => CTR => C1: 2,3
* INC C1: 2,3 # C5: 8,9 => UNS
* INC C1: 2,3 # C6: 8,9 => UNS
* INC C1: 2,3 # G1: 1,9 => UNS
* DIS C1: 2,3 # H1: 1,9 => CTR => H1: 5
* INC C1: 2,3 + H1: 5 # I1: 1,9 => UNS
* INC C1: 2,3 + H1: 5 # D4: 1,9 => UNS
* INC C1: 2,3 + H1: 5 # D5: 1,9 => UNS
* INC C1: 2,3 + H1: 5 # D6: 1,9 => UNS
* INC C1: 2,3 + H1: 5 # G1: 1,9 => UNS
* INC C1: 2,3 + H1: 5 # I1: 1,9 => UNS
* INC C1: 2,3 + H1: 5 # D4: 1,9 => UNS
* INC C1: 2,3 + H1: 5 # D5: 1,9 => UNS
* INC C1: 2,3 + H1: 5 # D6: 1,9 => UNS
* INC C1: 2,3 + H1: 5 # G1: 1,9 => UNS
* INC C1: 2,3 + H1: 5 # I1: 1,9 => UNS
* DIS C1: 2,3 + H1: 5 # G4: 1,9 => CTR => G4: 4,7
* DIS C1: 2,3 + H1: 5 + G4: 4,7 # G5: 1,9 => CTR => G5: 4,7,8
* INC C1: 2,3 + H1: 5 + G4: 4,7 + G5: 4,7,8 # G1: 1,9 => UNS
* INC C1: 2,3 + H1: 5 + G4: 4,7 + G5: 4,7,8 # I1: 1,9 => UNS
* INC C1: 2,3 + H1: 5 + G4: 4,7 + G5: 4,7,8 # D4: 1,9 => UNS
* INC C1: 2,3 + H1: 5 + G4: 4,7 + G5: 4,7,8 # D5: 1,9 => UNS
* INC C1: 2,3 + H1: 5 + G4: 4,7 + G5: 4,7,8 # D6: 1,9 => UNS
* INC C1: 2,3 + H1: 5 + G4: 4,7 + G5: 4,7,8 # I6: 1,9 => UNS
* INC C1: 2,3 + H1: 5 + G4: 4,7 + G5: 4,7,8 # I6: 7,8 => UNS
* INC C1: 2,3 + H1: 5 + G4: 4,7 + G5: 4,7,8 # I5: 1,9 => UNS
* INC C1: 2,3 + H1: 5 + G4: 4,7 + G5: 4,7,8 # I6: 1,9 => UNS
* INC C1: 2,3 + H1: 5 + G4: 4,7 + G5: 4,7,8 # D4: 1,9 => UNS
* INC C1: 2,3 + H1: 5 + G4: 4,7 + G5: 4,7,8 # D4: 4,7 => UNS
* INC C1: 2,3 + H1: 5 + G4: 4,7 + G5: 4,7,8 # G7: 1,8 => UNS
* DIS C1: 2,3 + H1: 5 + G4: 4,7 + G5: 4,7,8 # G7: 5 => CTR => G7: 1,8
* DIS C1: 2,3 + H1: 5 + G4: 4,7 + G5: 4,7,8 + G7: 1,8 # C5: 8,9 => CTR => C5: 4,7
* DIS C1: 2,3 + H1: 5 + G4: 4,7 + G5: 4,7,8 + G7: 1,8 + C5: 4,7 # C6: 8,9 => CTR => C6: 4,7
* PRF C1: 2,3 + H1: 5 + G4: 4,7 + G5: 4,7,8 + G7: 1,8 + C5: 4,7 + C6: 4,7 => SOL
* STA C1: 2,3 + H1: 5 + G4: 4,7 + G5: 4,7,8 + G7: 1,8 + C5: 4,7 + C6: 4,7
* CNT  35 HDP CHAINS /  34 HYP OPENED