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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4
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3answers
347 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 ...
6
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3answers
3k views

How can I solve this sudoku?

I've almost finished this hard sudoku, but I cannot finish it without guessing or making multiple blind steps to see if I'm wrong or not. Even https://www.sudoku-solutions.com/ gives up and says "...
3
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0answers
84 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 ...
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0answers
48 views

Most objective online linkable sudoku grader?

A Sudoku's difficulty level is often the first thing readers notice about a puzzle. For questions and answers showing a puzzle it would be nice to have a relatively objective linkable tester. I've ...
7
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1answer
169 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 ...
15
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2answers
3k views

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.), ...
10
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1answer
303 views

Is this 3d Sudoku possible?

I was looking at images of 3d Sudoku's on Bing, because I was looking for a $9\times9\times9$ Sudoku, where each horizontal, vertical left-right and vertical top-bottom plane was also a Sudoku. ...
2
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2answers
197 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 ...
9
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2answers
348 views

There's a wealth of information here. Make the most of it!

The puzzle below contains a wealth of information. However, if you were to make a list, you will soon realize that there's something missing. You're task is to fill in all the blanks. Have fun, and ...
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2answers
139 views

Numberless Sudoku with Just a Letter and Symbol Combination

A Standard 9x9 Sudoku uses the digits 1 to 9. You are only allowed to use a single letter(say T) and a symbol of your choice to represent the digits 1 to 9. Rules should be well defined and the ...
5
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2answers
169 views

Standard Sudoku Specialized with just 2 Primes

A standard 9x9 Sudoku uses the digits 1 to 9. You are only allowed two distinct primes to represent 1 to 9. Find out the minimum number of characters (digits + signs) needed to construct a Sudoku ...
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1answer
274 views

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 ...
0
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2answers
153 views

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 ...
0
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1answer
96 views

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.
2
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1answer
92 views

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 ...
24
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2answers
2k views

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.
8
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2answers
307 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 ...
5
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4answers
963 views

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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0answers
86 views

The hardest one I believe [duplicate]

If you are really smart solve this Sudoku within a day BEST OF LUCK
6
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2answers
298 views

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 ...
2
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3answers
689 views

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 ...
6
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1answer
286 views

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 ...
7
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2answers
175 views

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 ...
4
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9answers
3k 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 ...
5
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1answer
211 views

A Quick Sudoklu

Across ...
3
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1answer
157 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 ...
4
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4answers
376 views

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?
8
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1answer
220 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: ...
3
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2answers
190 views

Stuck on this Sudoku!

I have tried every trick I can think of... where am I going wrong?
4
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1answer
213 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
185 views

How do I proceed with this Sudoku puzzle?

Pairing elimination is done. What's next?
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1answer
277 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
2k 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?
0
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1answer
83 views

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 ...
11
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1answer
334 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-...
58
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3answers
2k views

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 ...
4
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1answer
181 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 ...
5
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2answers
197 views

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 ...
23
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2answers
794 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 ...
11
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1answer
450 views

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 ...
4
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1answer
198 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 ...
0
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1answer
498 views

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 ...
3
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0answers
302 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 ...
4
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4answers
247 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 ...
64
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2answers
5k views

Happy Pi-Day! Try to solve this “PiDoku”

To celebrate the Pi-Day (3/14) adequately, a challenging math puzzle must not be missing. Rules: Fill in the numbers 1-9 exactly once in every row, column, and region. On top of that, you need to ...
13
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2answers
1k views

Sudoku Construction Question

I'm one of a group of people building a big puzzle hunt. I have what I think is a pretty good idea for a puzzle, but I'm having trouble constructing it. Basically, what I need to do is make a sudoku ...
7
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2answers
249 views

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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2answers
201 views

Sudoku puzzle - where to go next?

Above is a link to a half-solved sudoku puzzle. I tried to fully solve it but just cant figure out what to do now. Source: Sudoku-Branium studios It is an app on google playstore.
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2answers
262 views

SUDOKU What next? [closed]

I have solved up to this point. How do I proceed without guessing?
4
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2answers
2k 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.