Stuck again - Puzzle 39

[Lively Ivy]

Hey all, I'm stuck again, this time on Puzzle 39. The hint says that placing a 3 in r5c7 forces r6c2 and r6c5 to both be a 3 (which is obviously impossible, elimiminating 3 from r5c7), but I don't see how this happens. Placing a 3 in r5c7 seems to place a 3 in r6c2 and 2 in r6c5, even avoiding placing digits in those cells and following other clues as they unwind. I also can't see any other way to progress. Could anyone help me see what I'm missing?

https://imgur.com/a/BfhLvsX

[Slod Vondo]

I'm also just about at this point...I'll check back if I find a path forward.

[Slod Vondo]

Solved - posted screenshot on Steam. I didn't use the hints, but I'm sure I made at least one intuitive leap to progress the puzzle forward. I'll have to dig in again with the hints and see if my own solve makes sense. I think after you place the 1 and 6 in Box 8 focus on Box 1,4,7... Start penciling Column 3 then box 1 and stuff starts to move along for a bit. You should be able to place a few numbers right away.

[Lively Ivy]

I fully marked c3 and box 1 and wasn't able to make any meaningful progress. I fully marked box 7 and using some ugly bifurcation and seeing what digits were placed no matter which numbers I placed in some pairs I was able to solve it. Almost certainly not the intended solution but hey it worked.

[Slod Vondo]

Originally posted by Lesbian Red:

I fully marked c3 and box 1 and wasn't able to make any meaningful progress. I fully marked box 7 and using some ugly bifurcation and seeing what digits were placed no matter which numbers I placed in some pairs I was able to solve it. Almost certainly not the intended solution but hey it worked.

Yes - it certainly didn't FEEL like an elegant solve. I'm going to come back to it for sure. I usually come back to these again and again until I can solve them in under 20 minutes...it's slow going but I love the puzzling aspect for sure. Game On!

[Slod Vondo]

Okay - it does have an elegant solution not requiring a leap of faith or bifurcation: There is ONE trick fairly early on that does a rather nice job of cracking it and one hidden pair later that could be a stall point. I'll post my notes on the solve after I translate my shorthand and verify that I have a good understanding of it. I'm in the middle of the re-work and I hit a snag with my own notes. I know it went fine, but what I wrote isn't translating in one part at the moment (frustrating for this amateur).

[Lively Ivy]

How do 7s in box 7 eliminate that 8? Couldn't 8 go in r8c2 while 7 goes in r9c1?

[Lively Ivy]

I'm also a bit confused by what you mean by the hidden 5/7 pair in r8. It seems 7 could be in r8c8 and 4 in r8c9, and I don't see would be eliminated from r8 in box 7 yet

Edit: I was able to figure it out by completing c7 - 6 goes in r9c7, meaning a 4 in r8c9 would eliminate all possible positions for 5s.

[Slod Vondo]

Originally posted by Lesbian Red:

I'm also a bit confused by what you mean by the hidden 5/7 pair in r8. It seems 7 could be in r8c8 and 4 in r8c9, and I don't see would be eliminated from r8 in box 7 yet

Edit: I was able to figure it out by completing c7 - 6 goes in r9c7, meaning a 4 in r8c9 would eliminate all possible positions for 5s.

I figured out the hidden 57 - it requires an extra step I need to annotate still. Once you pencil 4's in Box 9 and the 4's in Box 8 leave 2 spots for 4 in Box 7 pushing 5 down to R9C1 which should reveal the hidden 57 in box 9...then the rest should be butter!

[Slod Vondo]

Originally posted by Lesbian Red:

How do 7s in box 7 eliminate that 8? Couldn't 8 go in r8c2 while 7 goes in r9c1?

Because that 8 would see all possible 7's so if it was an 8 there would be no where for the 7 to go in that box.

[Slod Vondo]

Edited and Semi-checked. Below is the step-by-step (hoping my notation is comprehensible).

Puzzle 39 by the numbers
B5: Should be able to place 5,6,7 leaving 89 pair and 1,2,3,4 quad at the thermo bulb ends. And 3 of the 4 thermos get numbers in the second and 3rd cells of each thermo, the thermo going into Box 6 ends up with a 35 and a 58 pencil after the bulb.
Pencil Box 8 (Naked 1 then place 6) leaving 2,4,8 triple in R9
C3 pencil 2 in R1R2, Pencil 8’s in Box 4,1,7, Pencil 7 in Box 7 (eliminating 8 in R8C2 because it now sees all possible 7's in box 7) allowing placement of 8 in C3 and then 8 in Box 1
7 in B1 can only go in R2C1 (by sudoku) and 7 in B7 now only in R9C2. Place 3 in R9C3 and now 26 pair at top of C3
Finish pencil B1 (should now have 45 pair, 13 pair, and 26 pair), now 68 pair in R3 to complete the row.
This is where it gets fun and the real break in the solve: Pencil Box 2: IF R1C4 is 6 then R2C3 is 2 and R2C3 is 6, making R2C4 a 4 which makes R2C2 a 5 (placing it next to a 6) SO R2C4 must be a 6 allowing placement of 2 and 6 in Box 1.
Pencil Box 3: Naked 9 in R2C7 and then Naked 6 in C7
Pencil Box 9: Pay attention to 4 and 5, 4 cannot go in R8C9 as it sees all possible 5’s in Box 9 so 4’s in Box 9 push up to R7, creating 4 in R8C1C2 (which pushes 5 to R9C1 and THEN eliminates the 5 in R9C9 and revealing when penciling is complete in Box 9 the HIDDEN 57 pair in R8C8C9, leaving only 1 place for the 3 in R8 (R8C7) and pushing a 24 pair into Box 7 in R8. And with the 19 pair in Box 9 you also get a 24 pair in R7 box 9. Place a 3 now in R8 and clean up pairs in Box 9. Naked 5 now in C7 on Thermo and place a 2 to complete C7. Now 8 at end of thermos fixes 6 and 8 in Box 3.
Place 6,9 in Box 7, then 45 in Box 1, then complete Box 7
Place 4 in Box 2 and clean up pencils in Box 3
3 in R9C3 cleans up Box 8 (as 4 cannot be in R9C4), now cleaning up C6 and C4 and Box 2, leaves a 23 pair in Box 5
Place 6 and 8 in Box 4. Now 1, 2, 3 can be placed to complete Box 4 and 5.
Pencil 2’s in Box 6 allows placement of 2457 in Box 9 and 57 in Box 3 then you should be able to complete Box 3,6, and 9 to complete the puzzle.

[Lively Ivy]

Originally posted by Slod Vondo:

Originally posted by Lesbian Red:

How do 7s in box 7 eliminate that 8? Couldn't 8 go in r8c2 while 7 goes in r9c1?

Because that 8 would see all possible 7's so if it was an 8 there would be no where for the 7 to go in that box.

How would it see the 7 pencil mark in the corner? (r9c1)

[Slod Vondo]

Originally posted by Lesbian Red:

Originally posted by Slod Vondo:

Because that 8 would see all possible 7's so if it was an 8 there would be no where for the 7 to go in that box.

How would it see the 7 pencil mark in the corner? (r9c1)

Oh - snapdragon! That's a good point. I'll need to figure out how I did that. I have a feeling that it's an easy get (probably). . . Good to have a critical mind at the other end of this ramble.

[Lively Ivy]

Originally posted by Slod Vondo:

Originally posted by Lesbian Red:

How would it see the 7 pencil mark in the corner? (r9c1)

Oh - snapdragon! That's a good point. I'll need to figure out how I did that. I have a feeling that it's an easy get (probably). . . Good to have a critical mind at the other end of this ramble.

Everything else before and after that looks really good though! Thanks for helping me figure out how to solve it

[Slod Vondo]

Hint #4 seems completely wrong - I can see why you may have been pulling your hair out. I cannot for the life of me fathom the logic. I'm going to give this one a rest for the moment and maybe come back to it down the line. I solved it, but using faulty logic that seemed very elegant and right, so it couldn't be that wrong (right???). Maybe I'll grok it more when waiting is done.

[Tensai]

I just finished all 40 puzzles, what a ride!!
As for this particular one, you might want to know this trick https://youtu.be/e9_FkcNAZcA?t=292
but you can definitely solve it without it.