The New Sudoku Players' Forum

[813554]

Puzzle: https://imgur.com/a/Q5Dnd2N

I learnt a lot from this forum and I was able to solve my puzzles sooner or later but I really stuck in this. I'm pretty sure that I am missing something like a chain or X-wing whatever maybe naked or hidden triplets or pairs. I learnt 3D Medusa recently, I was really shocked when I used it for the first time, it was making it so easy. I tried it on this puzzle but there's not enough strong links. What am I missing? How can I solve this? Most importantly, what coloring technique I should learn to see patterns in puzzles like this?

Edit: Maybe I should check my pencil marks, they might be wrong. I'll do that.

[999_Springs]

there is a w-wing here with the 7's in column 4 and the 67 bivalue cells in r1c7 and r7c9

the idea is that wherever the 7 is in column 4 then one of the two 67 bivalue cells has to be a 6, so you can get rid of 6 from any other cell that sees either of those cells

in particular r7c7 isn't 6 and the puzzle goes to the end with singles

edit: 3d medusa hahahahaha. what is this 2006? nobody uses that (or bob hanson's solver) anymore it's considered as old-fashioned as westlife and avril lavigne and crazy frog. just call it colouring and from there it's a short step to learning about general nice loops/cycles/aic's or whatever you like to call them - so that you can use some weak links rather than only strong ones

[SpAce]

I learnt a lot from this forum and I was able to solve my puzzles sooner or later but I really stuck in this. I'm pretty sure that I am missing something like a chain or X-wing whatever maybe naked or hidden triplets or pairs.

W-Wing is the simplest answer here, just like 999_Springs already mentioned. I have nothing to add to that part.

I learnt 3D Medusa recently, I was really shocked when I used it for the first time, it was making it so easy. I tried it on this puzzle but there's not enough strong links. What am I missing? How can I solve this? Most importantly, what coloring technique I should learn to see patterns in puzzles like this?

Here I can help. 3D Medusa is a good starting point to learn the basic idea of coloring techniques, but as you noticed, it doesn't get you very far. David Bird's GEM is the answer you're looking for. It's the most powerful humanly applicable coloring technique I know, and it will solve puzzles like this (and far beyond) easily. David's original presentation and method doesn't make it seem very human-friendly (except for himself, I guess), but actually it is if you use a coloring tool (with a suitable mapping) or other simple mark-up to implement it. I use it both with pencil-and-paper (using a graphical mark-up I made up) as well as with Hodoku coloring. The latter is by far the quickest way to find chains and nets manually, and most of my solutions in the forum Puzzles section have been found using it -- typically in a few minutes. Here's an example of my GEM technique using Hodoku.

GEM coloring starts by identifying a strongly-linked cluster (or at least a pair) just like 3D Medusa (in fact, the initial cluster is a 3D Medusa in normal cases), but it extends far beyond Medusa because of the ability to follow weak links (and to use group nodes, ALSs, and basically any patterns). Below is an example of how it could be used to find the W-Wing and its eliminations in your puzzle:

gemex.png (65.96 KiB) Viewed 851 times

The bluish candidates represent the initial strongly linked par cluster (3D Medusa), and the reddish and greenish ones are the sub and super candidates resulting from following weak links. The dark and light shades of the colors represent the two opposite parities. The grayed-out candidates are found eliminations (they see par/super candidates of both parities; i.e. color trap). The same result could be found using some other seed clusters/pairs as well.

[SpAce]

edit: 3d medusa hahahahaha. what is this 2006? nobody uses that (or bob hanson's solver) anymore it's considered as old-fashioned as westlife and avril lavigne and crazy frog.

This proves that false

I just did it for the kicks of it, though But seriously, while 3D Medusa is a pretty useless technique by itself, it does work as a good stepping stone for more advanced coloring like GEM. Therefore, I think it's still a worthy learning tool.