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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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Introducing Domidoku!

Come one, come all! Come see the new type of logic puzzle, the Domidoku! Here's a sample for all to try! The process is simple! First you solve the Sudoku and then you solve the Dominosa! ...
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1answer
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How can I solve this Sudoku without guessing?

I am fairly new to Sudoku and have hit a brick wall with this one. My colleague said it can only be solved with a guess and seeing how far you go. However, I agree with many on this site and you ...
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2answers
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Stuck on this Sudoku puzzle. Please Explain the logic

I have completed this puzzle with the help of hints from the app. But I am not able to figure out the logic. I normally proceed by placing sure (unambiguous) digits first. Then repeat. But here I am ...
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1answer
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Minimum number of clues for Sudoku to have an unique solution? [duplicate]

I already know that 17 clues are a minimum for a Sudoku to have a solution, but I don't consider a Sudoku to be a real Sudoku while having more than one solution.
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1answer
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Help with Sudoku

i recently was playing sudoku on my iPad. As i was stuck on the puzzle i tipped on "Tip" to receive a hint on how i can solve this sudoku (I am still learning the game) - so please don't judge me for ...
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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?
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2answers
284 views

What other strategies can I use with this sudoku puzzle?

I have a sudoku puzzle that I have been doing for 270 hours. I never guess numbers and always thought that every move in sudoku had to have a logical explanation. Until the app generated this random ...
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Reversed Sudoku

Sudoku from Sudoku Solutions. Here's a Sudoku grid with all the obvious candidates removed. Your task is to re-supply the givens.
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Integers in Cells puzzle (sudoko-like)

All the whole numbers 1−9 are placed in the 9 triangular cells. A negative sign is placed in front of some numbers. The letters A−F are products of 3 or 5 of the numbers. Find all possible ...
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Sum in a sudoku with sum total of 15 and 45

I have created a sudoku puzzle with the following restrictions: Each row and column sum to $45$. Each row and column in the nine $3$ by $3$ sub-grids sum to $15$. Is such a sudoku unique?...
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The hardest one I believe [duplicate]

If you are really smart solve this Sudoku within a day BEST OF LUCK
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Sudoku puzzle #1

Please solve the following sudoku puzzle (from Wikipedia):
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Some Stratospherically Strenuous Sudoku

These three sudoku are particularly irksome, can you logically deduce the solutions to all (or any!) ...and provide your reasoning? They are all proper sudoku - each has a unique solution. They can, ...
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Are there published Sudoku puzzles that require guessing?

I believe in a number of books I have read and solved myself, the introduction stated that guessing should never be necessary for any of the puzzles in the book. Instead, a handful of techniques ...
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3answers
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How do I solve this sudoku without guessing?

I have filled all the possible singles. Also identified and shortlisted candidates, pointing pairs. How do I move ahead without guessing? PS: I applied "Nishio", choosing one of the two possible ...
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2answers
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This is a crossudoku 2

As a follow-up to the first This is a crossudoku puzzle, I decided to make a new one. Here are the clues: Horizontal: D2-F2 The sum of three consecutive prime numbers B3-E3, F9-I9 A novel by ...
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Sudoku and guessing : theory?

It has been proven that the minimum number of givens for a uniquely solvable classic 9x9 sudoku is 17. The usual solving method followed by people is : Fill all the cells where you are sure there is ...
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1answer
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Triple Homicide Sudoku

You are a special consultant who is brought in only for the toughest of cases. A serial killer has been on the loose and has struck the first day of the month for three months in a row now. Interpol ...
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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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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 ...
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R.H.P.C. crossword puzzle

This is an entry into the Fortnightly Topic Challenge #36 I got a ticket to the Red Herring Puzzle Club in the middle of the street. There was just a guy giving them out, like some advertisement ...
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2answers
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The Do-It-Yourself Puzzle

Can you solve this puzzle? You may (or may not) have noticed that this puzzle doesn't seem to have any pieces. How can it be solved without pieces? The short answer it can't. That's why for this ...
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3answers
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How can I spot an X-Wing?

I was doing a Sudoku puzzle (in my morning newspaper on the train to work) and got stuck at this point: ...
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9answers
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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 ...
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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 ...
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1answer
259 views

Generate a sudoku puzzle with minimum number of entries that has exactly $k$ solutions

Is there an algorithm to generate a sudoku puzzle having the minimum number of entries that has exactly $k>1$ solutions? What is this minimum number of entries, as a function of $k$? Given that ...
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2answers
773 views

Slightly Odd Sudoku

Someone I find very trustworthy continues to insist that this is a valid Sudoku board. It's been a while since I've played, but surely there's a couple of things off here, right? Alright, so that ...
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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?
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Is a 'legit' Sudoku puzzle supposed to be symmetrical?

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

Unusual Sudoku Puzzle

Find the solution to this Sudoku puzzle. The only problem is there aren't any normal Sudoku clues. Instead there are only some cryptic clues. What is the solution and how does the puzzle work? Edit: ...
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How many minimal-clue sudoku puzzles are there?

It is known that there are a minimum of 17 clues needed to create a proper sudoku puzzle. For how many puzzles is 17 sufficient? From the history of the minimal proof, I gather that there are ...
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Maximum Sudoku Puzzle

As most of you know, there is no Sudoku problem that has less than 17 number of starting clues with one unique solution. Imagine there is a sudoku problem that has $n$ number of starting clues with ...
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2answers
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Stuck on this Sudoku!

I have tried every trick I can think of... where am I going wrong?
11
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1answer
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Minimum number of clues for a sudoku puzzle

In a sudoku puzzle, what is the absolute minimum number of clues that must be given to specify a layout with a unique solution? Is one in each row, column, and box (9 total) necessary or sufficient?
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1answer
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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 ...
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2answers
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How do I proceed with this Sudoku puzzle?

Pairing elimination is done. What's next?
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1answer
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Help solve sudoku

I did solve this sudoku in 24 minutes, but I had to guess from this part out. I'm using a website to display this sudoku a lot neater than the original site. I can solve plenty of sudokus, but the ...
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1answer
277 views

The Vowel Sudoku Challenge

This is an entry into the Fortnightly Topic Challenge #36 Here is a partially filled in Sudoku-like board involving the five vowels: As with real Sudoku, no vowels in any 9-square box or along any 9-...
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1answer
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What should be my next valid move?

That's the stage I'm now. I am looking at G block (one in left down corner) 4,5 value. I couldn't decide if it should be 4 or 5. How do I decide? And, am I looking at the right place? Any alternate ...
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Save the Eggs! - An Angry Birds Puzzle (Part 2)

⬅️ Angry Birds 1 After saving the eggs, the birds are more cautious. Good News! You can finally relax and enjoy the birds’ hospitality. Unfortunately for you, you’re not the only visitor in town. ...
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1answer
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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
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Do multi-way jigsaw sudoku exist?

A Jigsaw sudoku is like a regular sudoku, but with uneven shapes instead of 9 squares. However, they still have the normal rules for rows and columns. Would it be possible to have a jigsaw sudoku ...
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463 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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1answer
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Maximize 'chains' in a Sudoku

Yet to be solved. Take 2 numbers such that $N, M \in \{1,2,3,4,5,6,7,8,9\}; N \ne M$. Start with a solved 9x9 Sudoku grid. Find any $N_1 = N$. Find an $M_1 = M$, in the same row as $N_1$. In the ...
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2answers
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Why is this considered to be “The World's Hardest Sudoku”?

NOTE: This is in reference to an existing question which I feel is poor and off-topic. In the spirit of "shaping the site while in private beta", I wanted show how the question can be re-phrased and "...
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1answer
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An Incomplete Puzzle

I'm sorry to offload some of my work as the puzzle creator on to you solvers. (No, I'm not.) At least there's only one clue missing, right? EDIT: When the puzzle is ready to be solved, there will be ...
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1answer
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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 ...
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4answers
240 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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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 ...