The New Sudoku Players' Forum

[Bigtone53]

The puzzle definelty required a computer to track all the candidates for each cell, so the 'tough' rating should of been upgraded in my opinion

CrazyGirl, are you saying that you rate the toughness by whether a computer is needed to track candidates, or that you use a computer to track candidates to actually solve the puzzle?

My way may not be for all, but I keep track of very few possibilities, even for this one.

[Crazy Girl]

Bigtone53,
I normally try to solve Killers in pencil but if i can't solve it, having stared at it for hours, and having a bad day, as a last resort I will attempt it on the computer where one can easily track candidates.

The three Deadly Killers in Books last week I managed to solve without the use of the computer. IMO Killers should be solvable with Pencil, Paper & memory, but one can use the computer if one wishes.

Then a new category of Extreme Deadly's with computer use needed to track candidates.

[Ruud]

While learning the Killer lingo and techniques, I tried this Times Killer from time to time, but I could not crack it.

Jean-Christophe's way to solve it seemed to difficult for a published puzzle. My aim was to find a path that does not require me to 'remember' the temporary results of various '45' tests.

Here is an alternative way that I finally managed to find:

Start with the easy pickings:

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45 on N3: Outie 4 in r4c9
45 on N7: r7c23=5, r7c3=4, r7c2=1. r6c3=9.

r789c1 = {689} locked

Check configurations and identify mandatory digits in cages.

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Cage 19/3 in N4 = {478|568}. 8 is locked in r45c2.

Cage 22/3 in N69 = {589|679}. 9 is locked in r7c89.

Cage 10/2 in N9 = {28|37}. Eliminate {16}

6 is locked in r7c789. r7c1=8.

cage 25/4 in N8 cannot be {4678}.
cage 25/4 requires 9. Locked in r8c56. r8c1 = 6. r9c1 = 9.

These are the key steps:

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45 on N8: r56c4 + r9c7 = 22/3 = {589|679}. r5c4=9.

Cage 10/2 in N8 cannot be {19}. r9c8 = 1.

N9: Cage 8/3 = {1}+{25|34}, 10/2 = {28|37}. {23} locked in 2 cages. r7c7 <> {23}

From here on, it is fairly simple.

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{23} locked in r7+N8

r9c45 = {46} locked
r9c67 = {57} locked. r9c9=8. r8c9=2.
r8c23 = {57} locked
r8c78 = {34} locked

Cage 25/4 requires 8. r8c56 = {89} locked. r8c4=1. r6c4=8. r7c4=2.

Cage 25/4 = {3589}. r7c56 = {35} locked. r7c7=6. r9c6=7. r9c7=5.

r7c89 = {79} locked. r6c8=6.
r6c67 = {12} locked
r6c12 = {34} locked

cage 13/2 in N5 = {67} r6c5=7. r5c5=6. r6c9=5. r5c6=4. r9c5=4. r9c4=6.
cage 19/3 in N4 = {568} => r4c2=6. r5c1=5. r5c2=8.

cage 16/4 in N45 = {1357}.
r45c3 = {17} locked. r8c3=5. r8c2=7. r4c1=2.
r4c45 = {35} locked. r4c6=1. r6c6=2. r6c7=1. r4c3=7. r5c3=1.

cage 15/3 in N3 = {249|348}. {4} locked in r123c7. r8c7=3. r8c8=4.

cage 15/3 in N3 = {249}. {9} locked in r123c7. r4c7=8. r4c8=9. r3c6=3.

r5c7=7. r5c9=3. r5c8=2. r7c8=7. r7c9=9. r7c6=5. r7c5=3.
r4c5=5. r4c4=3.

r3c89 = {56}. r3c8=5. r3c9=6. r3c3=8.
r3c12 = {19}. r3c1=1. r3c2=9. r3c5=2. r3c7=4. r3c4=7. r2c5=1. r2c4=5. r1c4=4.
r2c23 = {36}.

all singles from here.

This has been a great learning exercise!

Ruud.