Questions tagged [sudoku]

A Sudoku is a puzzle consisting of a grid to be filled with symbols, such that each constraining unit contains each symbol exactly once. The typical example is a 9x9 square to be filled with the numbers 1 to 9, where the constraining units are rows, columns, and 3x3 blocks.

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5
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1answer
158 views

All That Remains Sudoku

. 2 . | . 7 . | . . 9 . 9 8 | . . . | . . . 3 . . | 9 . . | . . . ---------+---------+-------- 2 . 7 | . . . | . . . . 1 5 | 7 . . | . . . . . . | 1 5 8 | . ...
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2answers
533 views

How to solve this Sudoku?

Here is the sudoku - I could think the following only. The top number box 3 coloumn wise should have some number - 6,7,3 (in some order). The box 3 column 2 -- 2,5,8 ( in some order), and box 3 ...
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9answers
5k views

Sudoku false positive (wrong move)

I'm new to Sudoku puzzles. I tried solving the one above but my last move was flagged as a wrong move(highlighted red). I believe it is a false positive since the $6$(highlighted red) I inserted is ...
4
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2answers
268 views

What is the maximum number of numbers a sudoku can have and have more than one solution?

I was watching this video where he talked about how scientists found the minimum number of numbers a Sudoku can have and still have exactly one solution. This led me to think of the opposite - what is ...
4
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2answers
886 views

What should be used to solve the next step of this sudoku puzzle

How to solve the next step in this sudoku ? I tried X-wing, hidden pairs and many other popular techniques found here http://hodoku.sourceforge.net/en/tech_hidden.php
4
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3answers
526 views

Was “Crook's algorithm” for Sudoku really only developed in the 21st century?

The following algorithm for simplifying (and very often completely solving) Sudoku puzzles: Label each cell with the set of all possible values it could take. Pick a row/column/block and for a value ...
4
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4answers
364 views

Do there exist Graeco-Latin Square style puzzles?

Sudoku, KenKen, and Skyscrapers are three examples of Latin square puzzles. In all three, players are challenged to complete a Latin Square, a NxN grid (typically 9x9) in which the numbers 1-N appear ...
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2answers
2k views

Hardest sum sudoku ever! (as well as how to solve them)

This sum sudoku is probably the hardest puzzle I've ever encountered, and I have made very little progress (a few cells or so). I found it in a book by Reader's Digest. The solution is given, but ...
4
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2answers
3k views

Is a 'legit' Sudoku puzzle supposed to be symmetrical?

Or phrased differently, are non-symmetrical Sudoku puzzles considered legal?
4
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1answer
470 views

Sudoku: Stuck, Need hint to move forward

I have applied the techniques I know to eliminate possible candidates. I'm stuck at this stage now, any hints to move forward are appreciated. I found this puzzle in Microsoft sudoku Android app.
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4answers
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Why is the following 7 in Sudoku a mistake - Newbie

I'm a newbie at sudoku. Why is the following 7 in Sudoku a mistake?
4
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1answer
201 views

Finding a number in this sudoku

I have been trying this sudoku for nearly 5 hours now but im unable to find any number further...If anyone could help me out i would be really grateful.. Note: The numbers in black are the prefilled ...
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2answers
3k views

Do I need to guess from here on this sudoku?

I keep staring at this sudoku puzzle and can't seem to find the next move. Is the next move a guessing move? I thought sudoku always has clear solutions, you just need to figure them out.
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2answers
1k views

How to check a partial sudoku solution

John has started a sudoku puzzle and shows me his completed work, asking whether he's made any errors. There are no obvious errors (a number repeated in a row or subgrid). I know of two ways to ...
4
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2answers
564 views

Reasoning behind next step in sudoku

As you can see in the image, I've been struggling with this sudoku for quite some time and I'm completely stuck. I'm sure I'm missing one standard trick which would make it easy to solve, but I can't ...
4
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1answer
163 views

How to test a sudoku solver?

I have created a standard sudoku solver using my own algorithm. It relies on a continuous scanning with occasional tuple/pair searching. I am looking forward to test if this works properly. I have ...
4
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1answer
142 views

What technique I should use now? [closed]

I am stuck here. I don't want solution for this, I just want to know the name of technique which will be used here to go ahead.
4
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1answer
276 views

Can you help me with a logic to solve this puzzle?

I know the concept of pairing and removed pairs but what other concepts should I use to solve this?
4
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1answer
205 views

Sudoku: need a traceable hint for the next number

Partially solved sudoku: ...
4
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1answer
137 views

Smudged Sudoku - help me solve it!

One late evening I was making my sudoku. I finally finished until water spilled all over the middle-right block. The only thing I remember is the numbers present in the block (but not their position):...
4
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2answers
140 views

Sudoku, unclear next logical step?

Solved up until here, I took the sudoku through an online solver and it seemed to use a guess and check strategy? Is that the only way of getting the solution or am I missing something?
4
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1answer
367 views

Is solving a puzzle using uniqueness invalid? [duplicate]

(I don't know if this is appropriate to ask here, since it's a bit of a soft question about puzzles, rather than a puzzle itself. I'm not certain about the tags either.) When I was first introduced ...
4
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1answer
214 views

Trying to build a sudoku related puzzle box, struggling to ensure that there's only one solution

I want to build a specific puzzle box. The physical side I have down, but I'm struggling with ensuring that there's only one valid solution. The box consists of 9 freely rotating bands, inscribed ...
4
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1answer
292 views

What is guessing? [closed]

The whole difficulty of solving puzzles like sudoku is doing it without guessing. Well, either without any guessing whatsoever or with little enough that a human can still make retractions and come to ...
4
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1answer
771 views

Empty Rectangles - Does the rule apply when the intersection takes place inside the box with the empty rectangle?

The Empty Rectangles method is a strategy for solving Sudoku puzzles. I have seen the description of this strategy here, I have the following question: Is there a problem if the other end of the ...
4
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1answer
264 views

Does “naked set” method always solve a sudoku?

Is always possible to solve a sudoku (that has a unique solution) using only naked pair/triple/quad methods? If not, what about using naked set and hidden set methods combined togheter? I need to know ...
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1answer
2k views

is there any sudoku puzzle combined with magic square?

As everyone know in Sudoku sum of each row and column is 45. so all Sudoku solutions are some kind of magic square. but my question is: Have anyone seen a Sudoku puzzle combined with the magic ...
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2answers
5k views

Examples of sudokus with two solutions [duplicate]

I need some examples of sudokus having more than one solution. Do these puzzles have any common things?
3
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2answers
422 views

Another Determinant Sudoku

sudoku-determinant have been described well here : The Determinant Sudoku I have created another one. Number in the center is the value of the determinant Numbers 0 to 10 are the values of the ...
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2answers
1k views

How to generate and count the 7x7 Latin squares

How many 7 by 7 Latin squares are there, and how can one generate examples of them? I am working on classes for a game, and typing in numbers manually from 1-7 in rows and columns from scratch is ...
3
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4answers
395 views

Help with a sudoku puzzle

I would really appreciate some help because I spent more than hours finding another number. It is supposed to be a very hard one but I started well and according to the key, my numbers are correct. Do ...
3
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3answers
118 views

What patterns could be applied in order to solve a Sudoku?

Related to this Q&A. I am looking for a pattern that could be applied in order to solve this Sudoku. The current patterns that I apply: Ensure that every digit appears once in every block Ensure ...
3
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2answers
140 views

Excluding number in a sudoku scheme

I have the following scheme: Please look at the lower left subgrid. The 8 may go in R7C1 or R9C1. If I put the 8 in R7C1 I'd have a 4 in R9C7 and a 5 in R8C7 If I put the 8 in R9C1 I'd have the ...
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5answers
763 views

What is the best way to solve this 6x6 sudoku? [closed]

I eventually used a trial and error method to solve it: Assume B1 = 2 C2 and F1 = 4 C3 = 2 F3 = 6 There are no candidates left for A3 This let me set B1 = 4 and hence solve the puzzle. But is there ...
3
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2answers
202 views

Stuck on this Sudoku!

I have tried every trick I can think of... where am I going wrong?
3
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1answer
1k views

Why is this Sudoku Skyscraper Failing?

I'm attempting to write a program that solves Sudoku puzzles using a variety of techniques. Up this point, I've only implemented naked singles and hidden singles (for rows and columns). I've been ...
3
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1answer
265 views

Non-Diagonal Pointing Problem

You can see the rules for pointing problem at this article. It has been clarified that there is no solution to this question. But, what if we remove the diagonal rule? is there any solution?
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2answers
113 views

stucked really bad with sudoku puzzle

Stuck with this for long time now, I have tried all the techniques yhat I know
3
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1answer
270 views

How many unique “miracle sudokus” are there?

The following "Miracle Sudoku" puzzle contains only two starting numbers, plus some additional rules that end up revealing the whole board: https://www.youtube.com/watch?v=yKf9aUIxdb4 (or Sudoku ...
3
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1answer
186 views

Can I swap two “yellow” corners on the same side?

The bottom two layers are solved, and the cross has been formed on the bottom layer. I am putting the corners in, ready to orientate them correctly, but I have two corners which need swapping. (The ...
3
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2answers
129 views

What am I missing in this Sudoku?

I think I am missing something in the instance below, since I could solve it only with a long-winded chain of deductions starting with the assumption that (coordinates are (row,column)): and ...
3
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1answer
474 views

An enigmatic sudoku

I entered the dungeon through a small, dark tunnel. After a seemingly endless walk I finally reached a small room. At the other side of the room, there was a big iron door. And in front of the door, ...
3
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2answers
837 views

What is a good notation for trial-and-error when solving Sudoku on paper?

When solving Sudoku on paper, I sometimes get to the point where I need to resort to guessing or bifurcation. At that point, I might guess one number, and continue solving, changing that guess if I ...
3
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1answer
178 views

What do you get when you mix a crossword and a sudoku?

For this CrosSudoku puzzle you must completely solve the sudoku grid below. To start the sudoku you must first figure out the crossword clues to get the starting numbers. Clue notation: x and y are ...
3
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2answers
823 views

Unsolvable sudoku net with maximum blocks

Definitions For a $9\times9$ grid $G$ (not necessarily respecting sudoku rules), a subset of cells $S$ is defined to be sudoku-friendly if the values in $S$ do not contradict the rules of sudoku. ...
3
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1answer
67 views

Setka - Complete grid using clues and sudoku-style logic; Theme - Fear Itself

This is a Setka puzzle; you can find more (along with a more detailed explanation of the rules) at our website, linked from our profile. Theme: Fear Itself How to play Setka, the short version: ...
3
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1answer
121 views

What is the technique I should use now to go ahead?

This is a partially filled sudoku from the Sudoku Expert app. I thought I learnt all tricks and techniques. But clearly there is something I don't know about.
3
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0answers
245 views

Minimum amount of clues for a 16x16 sudoku

I know that 17 is the minimum for a standard 9x9 (3x3 squares), but what about a 16x16 (4x4 squares) sudoku?
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0answers
96 views

Is there a Sudoku answer that has only a single minimal clue set?

User Abigail comments on the titling of "Do sudoku answers always have a single minimal clue set?" : I'd be surprised if there were a Sudoku which doesn't have at least 2 disjoint clue-sets. Well ...
3
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0answers
366 views

How to solve this puzzle?

I have solved the sudoku. Scratching my head on the second part. Any hints? It is not picked from any competition. One of my office colleagues usually post these types of puzzles on emails for fun ...