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4 comes up pretty early even if you haven't seen the trivia question. (I hadn't) so as long as you know that the green cells are all the same, the solution is unique. What's with the asymmetrical puzzle? Ugly!
X-wing on 6's, skyscraper on 7's just as you mentioned.
Clear as mud lol😂
XY-Wings will get easier to spot and solve with repetition. How long have you need solving Sudoku, Ted?
Your clickbait titles detract from otherwise interesting videos. There was nothing forbidden about how you solve this puzzle.
Thank you for the feedback. I appreciate it. What type of limit do you think there should be for competition puzzles?
This was kind of straight forward except for the red cell. My commeners method (since I'm not good with the advanced strategies) was the old trial and error method, knowing that the no.8 could only go to two places in box 7, I had tried both and came up with the solution. I have to admit that your method is more efficient. Thank God, I'm not about to enter a competition, I might if I take the time to listen to you. Once again thanks for another beautiful puzzle.
I am glad you liked the puzzle, George. Thank you for sharing your approach.
W wing Thank you
Nice job! Thank you so much for sharing.
I found this very easy, but maybe I just got lucky. Is there such a thing as a forbidden strategy in competition? I would say that anything goes, be it bifurcation, URs, two-way chains (a special form of bifurcation), brute force, playing blindfolded (perhaps no recommended), playing with an arm behind one's back, or whatever (25 = row 2 column 5): 25, 16, 65, 45, 61, 41, 58, 52, 43, 63, 85, 55, 54, 56, 36, 96, 76, 14, 29, 98, 34, 49, 47, 78, 97, 71, 13, 38, 18, 32, 93, 79, 74, 72, 94, 89, 67, 69, 19, 11, 99 (colours or Skyscraper; possible Remote Pair), 87, 39, 12, 91, 92, 21, 23, 81, 83, 31, 27, 17, 22. There was also a two-way chain, which I would have used if necessary: R8C7 = 6 → R9C2 = 9; R8C7 = 7 → R9C2 = 9. ============== Interestingly, R2C8, R8C2 and R8C8 are all redundant, providing us with a range of simple variations: 1) Remove the 3 from R2C8 (HoDoKu rating: Hard 580 ???). 2) Remove the 5 from R8C2 (HoDoKu rating: Hard 600). 3) Remove the 1 from R8C8 (HoDoKu rating: Hard 1380). 4) Remove both R2C8 and R8C2 (HoDoKu rating: 594 Hard). 5) Remove both R8C2 and R8C8 (HoDoKu rating: Hard 1534). 6) Remove both R2C8 and R8C8 (HoDoKu rating: Extreme 2184). 7) Remove all three (HoDoKu rating: Extreme 2098 ???). 8) Also remove R6C6 (HoDoKu rating: Extreme 2102). There are a couple of curious anomalies among the ratings, but they give a rough idea of comparative difficulty. I would say that puzzle 3 offers a good compromise between challenge and accessibility. Puzzle 8 is a bit of a beast.
I like how you removed some of the aesthetic givens to see how it affected the difficulty.
Isn't the X-Y Chain simply another name for X-Y Wing??
An XY-Wing is the shortest form of an XY-Chain. Anything longer than 3 cells is just an XY-Chain.
@@SmartHobbies ah thx
Got in 6:35 with little help at 7:45 and 8:00 about 6 and 7. Thanks for today! 😊
Nice job Ana! That’s fast.
I simply used an XY-Wing and finished it in 10 minutes.
Nice job finding an XY-Wing. I felt the advanced strategy at the end was pretty quick to find with the way the puzzle solved. Would you agree?
I found x wing and then xy wing having pivot in box 1.
Nice job!
Done Used an AIC type 2 starting frm box 9 then to box 3, box 1, box 7 where finally the cells in boxes 7 and 9 ( in row 9)were facing each other. [ 67--> 67-->16-->19-->79 ] Easy puzzle.
Nice job using AIC. I think some others found that one.
A *forbidden* strategy? I found an X-wing in 6s followed by a finned X-wing in 7s. The latter cracked the puzzle, perhaps aided by the former. 0:20 The finned X-wing in 7s removed the 7 and placed the 8 in the red cell. The X-wing in 6s removed a 6 from the red cell. I see the skyscraper in the grid that gave me the finned X-wing, and it also removed the 7 from the red cell. 6:30 At that position with the placed digits, I had the rest of the grid centermarked. My next step was an X-wing in 6s. (The inner one. I can also see the outer one now.) Following was the finned X-wing in 7s. (It included the same cells as the outer X-wing in 6s.)
Nice job John. I have not seen remote pair, skyscraper or XY-Wing required in Sudoku Grand Prix before. There seems to be an unspoken agreement about how hard the Classic puzzles can be.
Nice and easy puzzle. Solved it in 7:55. At 8:32 the skyscraper actually solves the puzzle because you can also remove the 7 from r9c9, as it also sees both r8c7 and r9c2.
Nice job, Laszlo. And you are correct, the Skyscraper also does the job. Thank you for sharing.
What did I do at that point where you get stuck without an advanced strategy? Simple - I bifurcated on 6 and 7 in box 9. Now to watch the video and find out how to finish without bifurcating...
Thank you so much for sharing. What made you pick the 67 cell in Block 9 to try bifurcating?
I know I go against the grain, but nothing's wrong with bifurcating.
@@SmartHobbies Just had a pair of 67s there, had to go one way or the other. But the remote pair thing is much better - thanks!
@@JohnRandomness105 Well, it's certainly what people do in timed competition, but I'm always up for learning how to get to the solution another way.
@@drengskap You are welcome. The reason I ask is that I have an extreme tutorial coming up on Forcing Chains, and choosing the right start cells to look for these chains is the first critical step. Thank you.
6.56 for me today, happy with that!
Awesome time, Paula. Did you have any problems finding the remote pair, or did you find something else?
I don’t get the logic behind why xy chains work. More specifically, why do bi values cells that share a value and see each other on the board allow you to link them together and continuously link them to other cells? In example one, when I tried to work backwards from the xy-chain between the 6-7 cell and the 6-1 cell, I checked what the values would be for each cell in the chain if either of those cells were the 6, and when the 6-7 cell was the 6, the chain didn’t work. Am I thinking about this wrong?
Possibly. The way I think about it is to start with the digit you are trying to eliminate (the 6 on this example) and look inside that first bivalue cell first (6-7). Then start working the chain with similar digits between cells and switching digits within the cells. Always end your last link within the last cell (1 to the 6). Another way to think about it is to say first cell is 6 and anything that sees is cannot be a 6. If it is not a 6, then work out all the values of the chain and you will see the last cell has to be a 6. Don’t put 6 in first cell and last cell to see what happens. Just use both values of the starting cell. Does that help?
@@SmartHobbiesthat makes a little more sense, thanks
Nice and relatively easy puzzle. Solved it in 11:22. I usually start with using Snyder notation, and then switch to filling in candidate in cells where I have 4-5 cells already filled in in the row, column, or box. I think this is the easiest way to find hidden singles because they will jump out (of course, you need to scan well to eliminate candidates). At 8:16 I noticed things in a different order, which made it easier, I think. The 2 in r9c2 limits 2 to column 4 in box 8, eliminating 2 from r3c4, placing it to r3c6. After this r5c6 is the naked 9. Also, 3 is now limited to row7 in box 9, placing 3 to r9c4. Then I noticed that 6 can only go to column 4 as well in box 8 (so rather than noticing the x-wing on 6s in columns 5 and 6, I noticed this by looking at the possible candidates in column 4, and noticing that 6 is limited to box 8). After this the puzzle solved liked you did.
Nice, Laszlo! Thank you for sharing.
I have to question if this is even a valid puzzle. It has multiple solutions. To begin with, the green cells trivia is beyond my understanding at this point. I will study it. I placed a digit 4 in column 9 row 2 instead of column 8 row 2, the rest of the fours I left till the end, and it all worked out with about three solutions. Give at at try if you will. My red cell was a 6.
Wow, George. What prompted your to try a 4 in another spot?
@@SmartHobbies Good question. Some investigating is required. I've got my homework to do, I'll let you know when I find the answer. I think it was the seven eight naked pair, somehow I figured that the seven eight pair would occur in box 3 column eight and box 9 in column nine, plus the 4 would not repeat because that would make it a triplet. These are my immediate thoughts, for me not knowing is part of the fun .
@@georgegamentzy1816 cool.😎
Ok, Timberlake, a question right from the start. What cured you to automatically review block 4 to find the 6?
Great question. I looked for density of given digits. I saw 4 givens in block 4 already with 2 more digits in the row and 2 more in the column outside the block. Hope that helps, Paula.
At first, I was shocked and disappointed to see that the asymmetrical grid had multiple solutions, but then I read the description, and all was well. My first four steps restored the symmetry, and the rest was very straightforward. Frankly, I would have preferred a symmetrical puzzle from the start, given that the trivia question, which I haven't read or heard, was redundant (61 = row 6 column 1): 61, 45, 36, 28 (symmetry restored), 76, 27, 94, 79, 64, 77, 83, 55, 16, 39, 25, 35, 84, 17, 33, 26, 34, 46, 66, 44, 67, 47, 62, 99, 98, 19, 31, 32, 51, 52, 42, 68, 48, 63, 43, 93, 88, 78, 89, 71, 81, 75, 85, 72, 11, 38, 59, 58, 29, 12, 91, 92, 21, 22, 18. Lately, I've been doing a lot of variations on your featured puzzles, but I haven't been posting them, as you don't seem to have time to look at them. I hope that's because you're too busy doing more important things.
I appreciate the puzzles, Julian. I have been out traveling quite a bit this summer and barely keeping up with my video schedule. I do plan to check out some of the puzzles you’ve made for potential video later this month.
I forgot to press start at the timer so I don't know my time, but it is probably about 7 or 8 min. It was very nice! Thanks 🤗
Great job. It may have been shorter than that!
Starting out, I wanted to try the solution before watching the video give information, and I ignored the trivia question issue because I couldn't find anything. I got nothing but major mental exercise, and some digits. Next step, I continued the video until I got to the trivial question. (Yes, it was trivial.) The digit associated was 1 -- the only non-zero digit in the answer, but only 1 green cell allowed a 1 -- given 1s barred it from the others. But I had 1 elsewhere in that block in my initial attempt, and when I retried it with 1 in the green cell, I quickly broke block 8. Okay, I played the ditz here. The actual digit is X, the number of the right answer, and the one digit I placed in a green cell. I'll try it again. (Later) The puzzle finally became straightforward.
It’s okay John. This was a new idea I came up with to make the beginning of the puzzles in my pack more fun. I plan to work on some other variations to make the puzzles uniquely satisfying.
If you ignore the rule regarding the green cells, you may get either the same solution or an alternate, almost identical solution, using what-if scenarios, both of which actually work ! At some point, you reach a point where the 7s in row 8 can only be in columns 1 or 9. If you put the 7 in r8c1, you get a solution where green cells r6c1 (easily identified early in the game) and r2c8 are 4s, and green cells r4c5and r3c6 are 5s. Either way, the red cell can be correctly identified as a 3. The alternate solution only affects the central vertical chute. The solution of all the other blocks remains identical. Fun challenge :) On the other hand, you do not need to answer the math question. If you know that all four green cells must be the same digit, just start the puzzle and you should be able to enter a 4 in r6c1 as your first solve.
Georges, you gave me a great idea that I plan to use in a future puzzle pack. Thank you!
I did not see the naked single. Not even close. lol
They can be tricky to spot, Greg. How long have you been watching the channel?
I just used the trial and error method. All those pairs in boxes one two and four were closely related, so I just assigned a value to one of them, of course I hit a conflict, then I was left with the other possible number and it all worked out. It was a painful solve but it kept me out of trouble. Thank you for this amazing puzzle!
I am glad you thought this was a great puzzle, George. I thought Sulphur did an amazing job with the construction. It is nice that you found a way to solve it. 👍🏻
Thanks for a wonderful puzzle. For my solution I used the XY-chain r2c1, r3c3 and r3c7 so I didn't need the W-wing.
Very nice find, Hans. Thank you for sharing your experience. How long have you been watching the channel?
Very hard Thank you
It could be tough if you are not familiar with the strategies. Have you solved puzzles with 2-string kites before?
Beautiful puzzle. Solved it in 17:26. With so many bivalue cells my approach is usually to use colors to track the two possible ways digits can be in those cells, using one color for the lower possibility and another for the higher: If r1c1 is low (8), then r3c3 is also low (7), and r2c2 is high (9). Otherwise each of these cells will have the other digit. Then we can immediately color the unknown cells in boxes 2 and 6. One can then easily see the 2-string kites that eliminate certain digits in box 5. Moreover, clearly r2c5 and r5c2 must have the same digit (both are the opposite of r2c2), and so this digit can only be in r4c6 or r6c4 in box 5. Since 4 is also a digit that can only go to these cells in box 5, we can eliminate any other digit from these cells, in particular, 3 from r6c4. Because of the cells in r5c2 and r1c6, one can deduce that r6c5 can be neither 7 nor 8, so it is 3, like in your solution. While I did not notice the 36 pair in row 5, if one has that, one can also notice that since r6c1 and r1c6 are also the same digit (opposite of r1c1), this digit can only go to r4c5 in box 5, so that digit cannot be 6. This places 6 to r5c4 and then 3 to r6c5.
Great job using coloring, Laszlo! I almost took that route. Thank you for sharing how it worked out for you.
Found 36 pair in row5. This got resolved very easily as if we focus on the positioning of 89's in row 1 and col1, we find that either both R1C6 & R6C1 are 8's or both of them are 9's .This places a restriction on the cell R4C5 of box 5 which can only be 8 or 9. Thus R4C5=89 , taking away one of the snyder 6's in box 5 and we get 6 at R5C4 which resolves the 36 pair in row 5. After that i used AIC's to further solve , although i took long to complete.
Cool that you figured out the 8/9 restriction in R4C5. I like how you worked through the logic. Thank you for sharing.
I chose the simple, slow and steady method to move forward from the point in question. I bifurcated for about 20 minutes until I noticed r5c6 could only be 7 or 8. It didn't take long after that filling in the cells in boxes 4,5,8 and 9 that could not be 7,8 or 9. This led to a 45 pair and a 68 pair in box 6 which placed 3 in r6c7 and started the cascading filling in of 789s. Don't get me wrong, I appreciate the insight into your technique. It's just not for me.
I appreciate your comment Grant. There were several ways to approach this puzzle, and no one way is right. Thank you for sharing. I hope to hear from you again soon. 😎
"The beauty of this puzzle" Oh my days! It was beautiful indeed. And a very hard puzzle! Thanks for the solve! 🤗
You are welcome. I thought this was brilliant logic used by Sulphur. Glad you liked it.
I found it hard, and got stuck for a time. Every once in a while, I saw an AIC that shaved off a candidate. Eventually, I focused on the middle block. Finally cracking it open: R6C5 had 37. 7 placed 8 in R5C6 and 9 in R2C5, vacating the 89 in R1C6 -- that was a Y-wing in reverse. 6:10 At this stage? Block 9 was centermarked in addition to the placed digits. I cornermarked blocks 5, 6, and 8. I centermarked column 6 and R8C4. I can see in my grid the 2789 quad that I didn't find until much later -- very much later -- that placed the 36 pair in the orange cells. My next step was spotting a (Sashimi) finned X-wing in 8s, blocks 2, 4, and 5, removing 8 from R6C45. 8:20 I'm pretty sure that the action I found much later in block 5 is what you'll find now. BTW, 7 and 9 weren't as restricted, so I found no corresponding finned X-wing in 7s or 9s. 10:50 This was after I centermarked the grid. If R6C5 is 9, it forces 7 vertically, 8 horizontally, and empties 78 cells. It also happens with R5C6, and with every cell that faces a common digit (7, 8, or 9) in both directions. R6C5 had 37, and later still, came what I described above in the 1st paragraph. 14:50 My Sashimi X-wing did the work of the skyscraper. The next step, of course, is the 789 Y-wing, removng 7 from R5C6. Instead, I saw 7 breaking R1C6 by removing both 8 and 9.
Nice analysis, John. This was a tricky one. Nice to hear you found a Sashimi X-Wing.
W-wing сразу решает эту головоломку.
Keen observation. Thank you for sharing. How good are you at spotting W-Wings?
@@SmartHobbies достаточно быстро. На дуплеты всегда обращаю внимание впервую очередь.
Probably the worst sudoku sword fish tutorial I've watched.
Could you give me some feedback on what I could have done better? I am always looking to improve my content.
Join the Smartie Party NOW 🥳to get the rest of this and other reward puzzle packs, ad free content, discord access, and so much more👉👉www.buymeacoffee.com/timberlakeB/membership Timestamps 0:00 Intro 00:25 It’s Solving Time 00:52 Filling Green Cells 01:37 Puzzle Story 02:15 Strategy #1 05:13 Strategy #2 06:33 Strategy #3 10:06 My Favorite SolvingTip 12:34 Strategy #4 14:53 Solving The Red Cell
Took just a minute and half shy of an hour, but I finally got there. Not too sure what the difference between bifurcation and a logic chain is, but I'm going to say that I used a logic chain to solve without resorting to using deadly pattern (that I 100% noticed in the first place... absolutely) once I reached your 7:00 min mark (my like, 20-30min mark lol) I focused on box 2 and box 8. If you make the middle cell in box 8 (r8c5) a 6, it forces a 6 in r1c6 which forces a 9 in r1c3 (note that this 9 would make a 68 pair in box 4 r4c3 & r5c3), The 9 in r1c3 forces a 9 in r3c8 causing r1c8 to be a 45. The 45 in r1c8 would then pair up with the 45 in r8c8. This pair would then result in 68 pair in c8 of box 6 (r4c8 & r5c8). Then you look back over at the 68 pair you made in box 4 - whoa it's an x-wing (that also counts as a deadly pattern now that I think about it)! But... what's that? The x-wing on the 68 pairs you just made in r4 and r5 would force box 5 to have two 3's in column 4. And, I may not be the best at sudoku, but even I know that is not allowed. Tripple, quadruple, quintuple check the logic and you can confidently conclude that the middle cell in box 8 (r8c5) can never be a 6. Which means it must be an 8 :) After that murderous process, it solves pretty quickly.
Nice deduction. Thank you for sharing. Mark Goodliffe would say that a logic chain is not bifurcation if you can see the whole chain to make your deduction, whereas bifurcation is just picking 1 of 2 choices and seeing what happens. How much have you watched Cracking The Cryptic?
It's only the second sudoku video I ever watched and all the tricks in it, I did intuitively for years(basically on every train ride).
Nice job. You seem to have a knack for Sudoku, and you might be ready for my advanced tutorial series. How familiar are you with Sudoku X-Wings and Skyscrapers?
@@SmartHobbies I looked into both techniques and I used the logic behind the x-wing but without knowing about the technique it's nothing I actively searched for. But I have never considered something like the skyscraper. Only way I could eliminate those cells before was by trial and error.
@@philw6056 Wow. I did not know or use any of these techniques until I started watching CTC and Sudoku Swami a few years ago. I hope I can help you move a little bit further down your Sudoku journey.
I clicked on CtC's link and found I had solved the puzzle before. I didn't remember it, not even after I began solving it again. One sign of either my improvement or the ease of the puzzle was how the puzzle collapsed and unraveled before I finished centermarking the grid. I filled out all but block 7. I was dreading that after block 3. I had placed the 25 in the corner of block 7, and I noticed around the corners the chocolate-teapot quad AB, BC, CD, DA. I began in block 9, perhaps because I noticed the 26 a couple cells over, and then eliminated the 2 and placed the 6 -- the first digit except for filling the middle row and column. I cleaned things up after that, letting the puzzle unravel a bit. A 14 pair in block 3 led to a 3569 quad in block 1 and gave me some more digits. I began filling block 7 before I noticed the 36 in block 1, and redid the loop starting there, removing the 3 and placing the 6. (I didn't notice that the same would have happened with the 59 until now, but I didn't need it. I also never found or needed any Y-wing, which you include in your list of strategies.) That second loop unraveled everything. Normally, I'm oblivious to telegraphing, but this was obvious enough that I found it. 7:50 At the Y-wing: I see it at the point of the pair and the quad in my grid. I didn't notice it then. I feel a bit silly now about my comment on the loop and the 59 cell. I'd already placed the 9, thanks to a triple in block 1. The second application of the loop resolved the triple, resolved the corner cells, and broke up the Y-wing. The END: Beginning the puzzle fully centermarked gives a certain advantage: one doesn't have to do Snyder notation, or populate the grid. One doesn't risk botching the process. My previous puzzle was Rangsk's NYT Aug. 7 puzzle. I reached a point where I'd irrevocably broken the puzzle. I backtracked to where the placed digits were correct. My centermarks had a deadly pattern. So I finally wiped out my cornermarks and centermarks, and recentermarked the grid. Surprisingly, an X-wing in 1s cracked the puzzle. NYT puzzles aren't supposed to feature X-wings. Later: I just noticed that a pointing pair in 1s would have done the job. (The story of my Sudoku life.)
I have been there with the NYT Hard before, John. I am glad you tried this older puzzle from Clover. I wish she made more Classics.
You could solve a 3 in block 8 before the doubles in block 1. :) Block 9 (13:15) a 9 can be placed above the number 1.....
Nice Roger. Thank you for pointing that out. 💪🏻
In response to your question about my next move after exhausting Sneider notation - I scratched my head, tried to make sense of the world, and then pressed play on your video to figure out what I was supposed to do lol.
Awesome 😃 Whatever works. I am here for you until you stop getting stuck on puzzles like this.
10:15 for me. I didn't give up and had a beautiful finish! Thanks 🤗
Nice job Ana!