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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6
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2answers
6k views

Techniques to Solve this Sudoku Puzzle

I have a sudoku puzzle seen below that I am trying to solve. I know I can punch this into some sudoku solver and get the answer but I am looking for techniques I can use to solve this. Any advice?
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4answers
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How do I solve the world's hardest sudoku?

This question is posted under the guidelines Don't worry too hard about restricting or regulating anything that isn't turning into a problem yet. If you don't agree that this question is on topic, ...
84
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2answers
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This new puzzle type needs a name

I believe I have invented a new type of puzzle... What is its name? Colour-blind-friendly version available here. Begin by solving the 16x16 sudoku; each of the digits 1-16 must appear exactly ...
12
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1answer
5k views

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?
56
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4answers
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What is the maximum number of solutions a Sudoku puzzle can have?

I've seen Sudoku puzzles that can be solved two different ways. Referring to a traditional 9x9 grid: Is it possible for a Sudoku puzzle to have more than two solutions? If so, what is the maximum ...
25
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4answers
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Another new puzzle type needs a name

For an example of how this type of puzzle works, see here... I believe I have invented another new type of puzzle... What is its name? Colour-blind-friendly version available here. Begin by ...
13
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3answers
825 views

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, ...
22
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3answers
2k views

There is a reason sudoku uses squares

There exists a 9x9 grid with the cells in one single row numbered 1-9 in order. The cells in the other 8 rows are initially empty. Note: The cells initially containing numbers can be in any one row;...
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2answers
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Alphabetical Sudoku

Who loves fish? Okay that might sound a bit weird but don't worry, I am still sane. Maybe. To answer the question you must complete the Sudoku below. A word will appear in the highlighted box which ...
37
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11answers
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Sudoku net that is always solvable

A sudoku net is a 9x9 grid where every cell is either (blank) or has a cross (block). A random solved sudoku is chosen. The net is placed on top of the sudoku (in any of the 4 ways). We can only see ...
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6answers
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What are the criteria for determining the difficulty of Sudoku puzzle?

What are the criteria for determining the difficulty of Sudoku puzzles? Is it a subjective estimation based on the author's experience, or are there any precise guidelines? For example, there are ...
51
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11answers
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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 ...
16
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2answers
634 views

This new puzzle type needs a name {5}

I believe I have invented a new type of puzzle... What is its name? Colour-blind-friendly version available here. Begin by solving the 9x9 sudoku; each of the 9 symbols ...
15
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2answers
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Do sudoku answers always have a single minimal clue set?

Suppose we have a solved sudoku, which was started from a minimal set of clues to its unique solution, i.e. 17+ numbers in specific locations, which we'll call set1. Is there a set2, (or set3, etc.), ...
15
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3answers
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Cryptic Sucrosswordoku

Maybe I'm a little bit evil. I've combined a couple of puzzle types in a novel way (to me, at least). I'll lay down some rules. The solution to the sudoku works exactly the way a normal 9x9 sudoku ...
8
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1answer
305 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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3answers
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What do chess and wordoku have to do with each other? - Clue Thirty-One

<<---First clue <---Previous clue (?) "Aha! That's it," you exclaim, still holding the papers. "The answer is obviously [redacted]." Having figured out the answer, you ...
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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 ...
4
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1answer
355 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 ...
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2answers
232 views

Magical Knight Moves with Effortless Ease in his Magical Kingdom

Magical Knight knows every Square of his Magical Kingdom. In many respects, he is like any other knight...Literary,Prime, Normal(makes same allowed chess moves). He is people Knight . As he traverses ...
77
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1answer
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Empty sudoku puzzle

The rules are the same as for a normal sudoku puzzle. The only thing different is that instead of numbers for clues, you have greater than/less than (> <) signs between the cells. Have fun solving!...
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3answers
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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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1answer
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Japanese Fusion Alphabet Soup

The Dish... ...is an intriguing blend, with a base of classic Western flavours, and a twist of the Orient at its heart. The Ingredients... ...are diverse and are combined in such an unexpected - dare ...
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2answers
873 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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2answers
3k views

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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3answers
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The Determinant Sudoku

The determinants of $2\times 2$ matrices are calculated this way: $$\det\begin{bmatrix}a & b \\c & d \end{bmatrix}=ad-bc$$ And here's the sudoku-determinant puzzle: What's the solution for ...
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2answers
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Introducing: Compoundoku!

Rules of Compoundoku: Solve both left and right Sudokus. In addition, the board below them is the Compound Board of both Sudokus. Each number on the Compound Board should tell either: (1) ...
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2answers
818 views

Tetromino Sudoku

An entry in Fortnightly Topic Challenge #32: Grid Deduction Hybrids The grid below, when filled in, forms a valid Sudoku grid. It can also be filled in like a LITS (nuruomino) puzzle without the 1x4 ...
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2answers
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A 16 Clue Sudoku Puzzle (but the kings can't be in check)

An entry in the 19th fortnightly challenge... Above is a 9x9 "chess" board with some pieces already laid out, your goal is to fill the board completely, following standard Sudoku rules (i.e. every ...
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2answers
579 views

A Minesweeper Sudoku

My brother created this puzzle, and he wanted me to post this here. Each 3x3 box contains three mines (those squares also have numbers in them). There are no mines in boxes containing a 1, 2, or 3. ...
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4answers
3k views

After here should I guess or is there a logic solution on Sudoku?

From this point is it necessary to guess or is it possible to find a logic solution?
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9answers
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A Page of Puzzling

I found this puzzle page from a newspaper and found it absolutely confounding. The sudoku had question marks and other things all over it, the logic puzzle made no sense, the cryptic crossword was ...
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2answers
1k views

Pseudoku: A Game of Finding Order in Chaos

You are Pat Doe, a lowly Sudoku puzzle-maker eking out a living by producing hand-made Sudoku puzzles. After an exhausting eight hours, you've just completed your last Sudoku grid for the day. ...
22
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1answer
314 views

Monument Valley Sudoku

Another Sudoku monstrosity from the brains of Yours Truly. No rules are given, part of the challenge is trying to work out what the rules are :)
26
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1answer
2k views

This is a crossudoku

So, this is a crossudoku. It is the same as a sudoku - same rules apply. However, you have been given crossword-like clues for part of the numbers on the grid. Some of the clues may have multiple ...
17
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1answer
1k views

Sudoku with only 8 predefined numbers

Have fun with my self-made Sudoku puzzle. Solve this Sudoku puzzle using the standard Sudoku rules: Fill any row, column and bold-framed area with the numbers 1 to 9. Hint: It is not as difficult as ...
16
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2answers
961 views

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. ...
13
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2answers
732 views

Sudoku variation: Using various chess moves, solve the grid from just two numbers

I've been watching a youtube channel hosted by puzzlers and attempting the sudoku variation they post each day. Today's I found particularly interesting and while sharing it around it proved quite the ...
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2answers
921 views

Complaint at the PSE lounge

While walking through the PSE lounge, I noticed a piece of paper on one of the tables. Picking it up, I saw several things. The first, was a couple of sentences at the top: I love this place! But ...
12
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1answer
841 views

This new puzzle type needs a name {4}

I believe I have invented a new type of puzzle... What is its name? Begin by solving the 16x16 sudoku; each of the digits 1-16 must appear exactly once in each row, column and thick-bordered 4x4 ...
8
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2answers
837 views

A spartan skeleton Sudoku

A skeleton crossword is a crossword where the black and white squares aren't given; you have to deduce them. Here's a generalisation of that idea to the Sudoku puzzle. Here's a 4 by 4 grid, with four ...
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5answers
507 views

The Numberphile Heist (part 1)

Hello Puzzling Stack Exchange! While part 1 of the PSE School of Enigmatics remains unsolved, I've got part 1 of another puzzle series for you to solve. I'm in no way affiliated with Numberphile; ...
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1answer
264 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?
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Why must a sudoku have a unique solution [closed]

Why must a sudoku have a unique solution. In my books I don't guarantee it. But I am sure there are not many which don't. I doubt if one in a thousand dont have. And even if they don't its only a ...
14
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2answers
606 views

Double n-queen puzzle, with sudoku rules

Put 9 blue queens and 9 pink queens, with rules : If the blue queens removed, each pink queens do not attack each other. If the pink queens removed, each blue queens do not attack each other. Each 3×...
12
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1answer
6k views

Write digits 1 to 9 in the table, each pointing to next 3x3 grid

Write 1 to 9 digits in an empty Sudoku table with these rules (similar to 9-Queen problem): There are 9 Boxes indexed from 1 to 9 in the image below. and each box has a 3x3 grid child. Every two ...
9
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1answer
630 views

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 ...
9
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2answers
616 views

Cryptic Crossword Sudoku

This puzzle is inspired by Matt’s excellent Cryptic Sucrosswordoku. Below is a sudoku as well as some cryptic clues. The clues lack enumeration and are in no particular order. The solutions to the ...
9
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2answers
569 views

Tetromi-nuri-doku

Note: This puzzle was inspired by the one here, by Mike Q. Every square in the grid above, when the puzzle is complete, has a number between 1 and 9 in it and either is shaded or is not. Each 3x3 ...
7
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1answer
180 views

Maximum number of disjoint clue-sets that determine the same Sudoku solution?

"Do sudoku answers always have a single minimal clue set?" No. Solved Sudoku puzzles may have more than one set of disjoint clue-sets. And those clue-sets can vary in difficulty, so one might be ...