How to solve a sudoku using 'The law of Symmetry' ?

Piatato has carved out an absolutely mindboggling classic with a trick known only to a few in the sudoku world. So what are you waiting for ?
Try it out and check out the video !

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Rules :

Place a digit from 1 to 9 in each empty cell so that each digit appears exactly once in each row, column and 3x3 box. Classic Sudoku rules apply.

Hello Everyone ! Welcome to this Youtube channel :
"Unshackling Sudokus & Puzzles "
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I am Kishore Kumar Sridharan and I have been part of the team representing India in the World Sudoku Championship each year since 2015. I have also won the Classic Sudoku Master Event held during the Indian Sudoku Championship for a streak of 4 successive times. Solving sudokus and puzzles is my passion.

[JohnSmith-wxrw]

9:29 for me. After all the possible pointing pairs, I then determined all the combinations for row three. It was east to see that 1 and 4 were in box 1 row 3. From there the rest of the numbers were easily determined.

[laszloliptak]

This is a very nice puzzle. I solved it in 12:04.





I don't really like using uniqueness as a solving technique, though technically it does find a solution (which is all these puzzles ask for) without proving that that is the only solution. By the way, one can argue as follows that there is a rotationally symmetric solution as long as the givens satisfy the symmetry you described: In the final solution take all the digits above the main diagonal, and rotate them by 180 degrees, changing each to its corresponding digit. This will be a solution, and satisfy all the givens.
I solved the puzzle as follows: Notice that 1 has only two possible places in box 1, and three places in boxes 7 and 9. Similarly 2 has only two places in box 9 and three places in boxes 3 and 1. If 1 is in r3c3, it forces 1 to r9c2 in box 7, which forces 1 to r8c8 in box 9. This forces 2 to be in r7c7, which forces 2 to r1c8 in box 3, forcing 2 to r2c2 in box 1. The other possible place for 1 in box 1 is also r2c2, so r2c2 must be either 1 or 2, eliminating 8 from there, placing 8 into r2c1. Similarly one can get that r8c8 must be 1 or 2, eliminating 9 from there, placing 9 into r8c9. This leaves only one place for 9 in row 3, and for 8 in row 7. After this the puzzle solves very easily.
I find that pencilmarking cases when a digit can go into three positions is often helpful. I know that Simon a Mark from Cracking the Cryptic also don't do that in a classic sudoku, only in variants, but I like to do that and they really helped me in this puzzle to find the solution quickly.

[SmartHobbies]

Thanks for featuring this. It took me a while to find the break in. I ended up looking for AIC's and found a couple of Nice Continuous Loops using the 2's that cracked it. I need to feature this setter's puzzles on my channel as well.

[KitchensbySavina]

I like pure Classics the best. Thank you.

[TalkingInTheDark]

Nice puzzle guys. I did spot the symmetry which gives the 3 in the middle and from there it was pretty straightforward. Keep up the good work.

[atulkumarparikh]

This is somewhat unique concept of sudoku solutions.You must give atleast two more such puzzles

[JohnRandomness]

The puzzle seems symmetric under 180-degree rotation plus the following switches: 12, 33 (no change), 57, 89, and 46. Therefore, a unique solution must be symmetric under those changes. If a solution is not symmetric, then a second solution arrives from making those changes. I will try the puzzle, although I will try to avoid assuming uniqueness. (That should be proven.)

I find it useful to pencil in three options in a box as well as two, for various reasons. The one disadvantage is clutter.

I suppose that bifurcating on a two-value cell is as bad as assuming uniqueness and placing a 3 in the center, but that's what I did. One possibility led to multiple collisions while the other didn't. Also both trials led to a certain cell being the same (8). So I placed that, and the rest of the puzzle was straightforwardly solved.

[tsujaya]

Not understanding law of symmetry ..how you are getting 3 in the centre of 5 th box...?how to imagine rotation of first grid in order to know 9 and 8 are symmetrical ..this is very confusing..can you draw some diagram to illustrate the symmetricity of 9 and 8 and other digits also

[robertrisk]

Hi, how can I direct message you? Do you have an IG or FB page?