The TH-cam algorithm threw this at me just now, for some reason. Isn't it extraordinary how much has changed in four years? Your confidence, the video quality, the software(!), the community, the puzzles, the setters, the everything. It's genuinely remarkable, when you do a side-by-side comparison, and there's no disrespect in there at all to your 2019 content. I don't suppose anyone will see this comment after all this time, but my hat is off to you, Mark, and everyone in the community who has contributed to this wonderful evolution.
Seeing your struggle makes me feel a bit better about my own solving (in)abilities and frustrations. Thanks for the tips provided in this puzzle. I have learned so much from your solving techniques over the past year.
This is the best explanation of this technique I've ever heard. I developed on my own the same thing, only using pairs of the same numbers - odd number of links means you can eliminate the number from cells visible by both end points. Never considered using it with sets of numbers that are not the same pairs though! Your missing the obvious 4 in the middle cell of the bottom left block was driving me crazy... 30 seconds in, I saw it & literally pointed it out; 17 minutes later... ;-) =)
Agreed. I like to fill in all the simple ones first then move on to pairs etc. After two cups of tea and toast he says ... "That's how you solve an inverted sharkfin swordfish and of course it can only be a four"...LOL ...great guy.
Sir, You explained the Either Or technique very well. What I could understand from your explanation is if a double (or also called twins) is there is in a cell, then Either or Or option should result in a candidate in another cell becoming either True or False whether the two of the double or true or false. At video time 14:43, you explained that double (5,7) in cell R8-C8 can have two options. Option 1 is 5 is true. Then go along Row 8 and in double 5,8 in cell R8-C3, candidate 8 becomes true. Then go up along column 3 the double 1,8, candidate 1 becomes true. Then go along row 4 in cell R4-C4, candidate 7 becomes true. The Option 2 is to make the other candidate in starting cell R8-C8 which contained 5,7 now will have 7 as true. In that case, go up along column 8, you find out of triple 1,3,7, you can eliminate 7. Therefore in row 4 you have 7 again in cell R4-C4 becomes true. The logic to my mind is whether the cell R8-C8 with double 5,7 contains 5 as true or 7 or true, the net result is 7 in cell R4-C4 becomes true. Am I correct Sir?
The eights in columns seven and eight were never used from the beginning just like the fours were missed. Awesome how even someone so smart and talented can miss the obvious! We plebes must forgive ourselves!
Thanks again. Very much appreciate your explanations on chaining. They are not always easy to spot by when still learning. Also very helpful just to see how you attack the puzzle ie which parts to focus on now vs what to leave to later. Lastly, I recently saw one of your colleagues on Cracking the Cryptic follow a "minimal pencil marks" approach which seems to run counter to your comments on using pencil marks. From that contrast, could you comment on which pencil marks are more valuable than others and why. Many thanks. I really enjoy your vids.
Sir, I admire your explanation of even complex Sudoku techniques. In this video at time 9:38, you explained the logic of Either or technique. You said column 3 has two candidates 5. Therefore one of them has to be true and the other is false. That is this pair of 5s is a conjugate pair. You assumed for example candidate 5 in cell Row 5 Column 3 (R5-C3) is true (this means the other 5 in column 3 is false), then 5 in cell R6-C6 is true. Thus the candidate 5 out of 5,9 in cell R8-C6 is false. You therefore get 9 as a digit in that cell. The other choice is 5 in cell (assumed to be false in earlier case) is now True even then 5 in cell R8-C6 (5,9) is to be eliminated being false. Therefore whether any of the two 5s in column 3 is true, 5 in cell R8-C6 has to be false. Is this interpretation correct Sir?
The second chain you found (r6c8 or r5c5 is 6) eliminates not only 6 from r5c8. Ends of chain also see r5c7 and r6c6 which resolve 56 pair in box5 and cracks the puzzle already at the stage. I was waiting for you to notice, but unfortunately you walked around and switched to other things.
@Simon Anthony. So confused at 8:54. You says "If" it's not a five. What if it IS the five, you then have a one above and still left with a 5/6 pair in the middle. Sorry if that's a stupid question! Bit of a newb to sudoku
Because if it's a five, it rules out the five in L8C6 (he probably didn't mention it since it's so visible for decently experienced players (no offence)), and if it's not, well it's still ruled out from the same position as he demonstrates through the chain Hope that's clearer
I was with you until you eliminated the '3' in row column 8. In that spot, I had the possibility of 3,5,6 but what still hangs me is the cell in row 5 column 7: I have in there as a remaining possibility, a 4 and a 3. for now, I cannot logically get rid of the 3. I have been working this puzzle for a week now. I'm going to reset and try again....
Never mind. I was able to work it out. The cell in row 4 column 8 cannot have a 5,6,or 7 and you just proved that the cell in row 5, column 8 cannot have a 5,6, or 7. That leaves only 1 and 3. That would eliminate the 3 in row 5 column 7. I did not think it all the way through.
Well instead of constantly doing pencil marks and start off with it, why not just look for given numbers doing basic sudoku? I found a few numbers right off the bat without doing marks just by looking for like 10 seconds
the moment when i resolvet on my own, but at the end the result is little bit different then in video.. and i cheked 5 times and i cannot find any mistake in my answer.. so it could be that there are 2 right ways to resolve this puzzle?
982-571-634 614-293-587 537-486-129 -------------------- 863-142-975 475-968-312 129-735-468 -------------------- 396-857-241 248-319-756 751-624-893 or maybe i did some mistake, but i cannot find it..
@@jadesininen My app tells me it cannot work with 634. But it does a uniqueness test which flushes out extra solutions. Just google that. I can't help you out any more without seeing the rest of you solution.
@@jadesininen, when you compare your solution to the actual puzzle, you made one mistake in copying the givens. In row 9, column 3, you have a 1, but in the puzzle itself, that digit should be a 3. Otherwise, your solution is valid.
Seeing your struggle makes me feel a bit better about my own solving (in)abilities and frustrations. Thanks for the tips provided in this puzzle. I have learned so much from your solving techniques over the past year.
The TH-cam algorithm threw this at me just now, for some reason. Isn't it extraordinary how much has changed in four years? Your confidence, the video quality, the software(!), the community, the puzzles, the setters, the everything. It's genuinely remarkable, when you do a side-by-side comparison, and there's no disrespect in there at all to your 2019 content. I don't suppose anyone will see this comment after all this time, but my hat is off to you, Mark, and everyone in the community who has contributed to this wonderful evolution.
I have seen your comment!
Seeing your struggle makes me feel a bit better about my own solving (in)abilities and frustrations. Thanks for the tips provided in this puzzle. I have learned so much from your solving techniques over the past year.
This is the best explanation of this technique I've ever heard. I developed on my own the same thing, only using pairs of the same numbers - odd number of links means you can eliminate the number from cells visible by both end points. Never considered using it with sets of numbers that are not the same pairs though!
Your missing the obvious 4 in the middle cell of the bottom left block was driving me crazy... 30 seconds in, I saw it & literally pointed it out; 17 minutes later... ;-) =)
Agreed. I like to fill in all the simple ones first then move on to pairs etc. After two cups of tea and toast he says ... "That's how you solve an inverted sharkfin swordfish and of course it can only be a four"...LOL ...great guy.
Very reassuring to hear that the fancier tricks I can neither remember nor spot, are not absolutely required to solve "difficult" puzzles. Thanks!
Sir, You explained the Either Or technique very well. What I could understand from your explanation is if a double (or also called twins) is there is in a cell, then Either or Or option should result in a candidate in another cell becoming either True or False whether the two of the double or true or false. At video time 14:43, you explained that double (5,7) in cell R8-C8 can have two options. Option 1 is 5 is true. Then go along Row 8 and in double 5,8 in cell R8-C3, candidate 8 becomes true. Then go up along column 3 the double 1,8, candidate 1 becomes true. Then go along row 4 in cell R4-C4, candidate 7 becomes true. The Option 2 is to make the other candidate in starting cell R8-C8 which contained 5,7 now will have 7 as true. In that case, go up along column 8, you find out of triple 1,3,7, you can eliminate 7. Therefore in row 4 you have 7 again in cell R4-C4 becomes true. The logic to my mind is whether the cell R8-C8 with double 5,7 contains 5 as true or 7 or true, the net result is 7 in cell R4-C4 becomes true. Am I correct Sir?
i was so waiting for the four in the bottom left, i missed almost everything else. :D
i have to say i was able to single out the 6/7 in square 6 and from there on solved the others.
This really helped move me one step further in my solving abilities. Thanks!
Good to see the use of the chain several times. Perhaps I'll be able to remember it for my own use.
Thanks At the beginning you could have put 4 in bottom left. Maybe not much help but I prefer to do all the basics first
The eights in columns seven and eight were never used from the beginning just like the fours were missed. Awesome how even someone so smart and talented can miss the obvious! We plebes must forgive ourselves!
Thanks again. Very much appreciate your explanations on chaining. They are not always easy to spot by when still learning. Also very helpful just to see how you attack the puzzle ie which parts to focus on now vs what to leave to later. Lastly, I recently saw one of your colleagues on Cracking the Cryptic follow a "minimal pencil marks" approach which seems to run counter to your comments on using pencil marks. From that contrast, could you comment on which pencil marks are more valuable than others and why. Many thanks. I really enjoy your vids.
Sir, I admire your explanation of even complex Sudoku techniques. In this video at time 9:38, you explained the logic of Either or technique. You said column 3 has two candidates 5. Therefore one of them has to be true and the other is false. That is this pair of 5s is a conjugate pair. You assumed for example candidate 5 in cell Row 5 Column 3 (R5-C3) is true (this means the other 5 in column 3 is false), then 5 in cell R6-C6 is true. Thus the candidate 5 out of 5,9 in cell R8-C6 is false. You therefore get 9 as a digit in that cell. The other choice is 5 in cell (assumed to be false in earlier case) is now True even then 5 in cell R8-C6 (5,9) is to be eliminated being false. Therefore whether any of the two 5s in column 3 is true, 5 in cell R8-C6 has to be false. Is this interpretation correct Sir?
Good job
at 6:45 I can see 2 numbers : first 4 in row 8 col 2 and 7 in row 1 col 5
The second chain you found (r6c8 or r5c5 is 6) eliminates not only 6 from r5c8. Ends of chain also see r5c7 and r6c6 which resolve 56 pair in box5 and cracks the puzzle already at the stage. I was waiting for you to notice, but unfortunately you walked around and switched to other things.
Excellent, thanks
Great Game i love Sudoku thanks for the video
@Simon Anthony. So confused at 8:54. You says "If" it's not a five. What if it IS the five, you then have a one above and still left with a 5/6 pair in the middle. Sorry if that's a stupid question! Bit of a newb to sudoku
Because if it's a five, it rules out the five in L8C6 (he probably didn't mention it since it's so visible for decently experienced players (no offence)), and if it's not, well it's still ruled out from the same position as he demonstrates through the chain
Hope that's clearer
@@GardIsPureOwned Of course, that's so obvious now!
I got stuck solving the NYT hard puzzle today (27/1/19). Could you please have a go. I can send you a screen shot of where I got stuck.
I was with you until you eliminated the '3' in row column 8. In that spot, I had the possibility of 3,5,6 but what still hangs me is the cell in row 5 column 7: I have in there as a remaining possibility, a 4 and a 3. for now, I cannot logically get rid of the 3. I have been working this puzzle for a week now. I'm going to reset and try again....
Never mind. I was able to work it out. The cell in row 4 column 8 cannot have a 5,6,or 7 and you just proved that the cell in row 5, column 8 cannot have a 5,6, or 7. That leaves only 1 and 3. That would eliminate the 3 in row 5 column 7. I did not think it all the way through.
Comment avoir la main pour jouer et trouver la solution.j'attends la réponse,merci
Well instead of constantly doing pencil marks and start off with it, why not just look for given numbers doing basic sudoku? I found a few numbers right off the bat without doing marks just by looking for like 10 seconds
the moment when i resolvet on my own, but at the end the result is little bit different then in video.. and i cheked 5 times and i cannot find any mistake in my answer.. so it could be that there are 2 right ways to resolve this puzzle?
982-571-634
614-293-587
537-486-129
--------------------
863-142-975
475-968-312
129-735-468
--------------------
396-857-241
248-319-756
751-624-893
or maybe i did some mistake, but i cannot find it..
@@jadesininen My app tells me it cannot work with 634. But it does a uniqueness test which flushes out extra solutions. Just google that. I can't help you out any more without seeing the rest of you solution.
@@jadesininen it comes out with 2 9s in r79c2, 2 fives in r58c3, 2 8s in r89c7 and 2 1s in r45c8
@@jadesininen, when you compare your solution to the actual puzzle, you made one mistake in copying the givens. In row 9, column 3, you have a 1, but in the puzzle itself, that digit should be a 3. Otherwise, your solution is valid.
it's like brute forcing all double grids...
👍
Bonne chance
Very strange, I solved this puzzle and got a different solution :/
Seeing your struggle makes me feel a bit better about my own solving (in)abilities and frustrations. Thanks for the tips provided in this puzzle. I have learned so much from your solving techniques over the past year.