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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Mystery Sudoku = new variant [closed]

I have created a new sudoku variant: the Mystery Sudoku. One of the 9 digits is the mystery digit. Try to find its value and its locations. The numbers outside the grid are the sum of 2 (at the bprder)...
6
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2answers
152 views

Spidoku - Fill in the rest?

Each of the eight segments of the spiderweb should be filled with a different number from 1 to 8, in such a way that every ring also contains a different number from 1 to 8. Some numbers are already ...
0
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3answers
174 views

Sudoku Move Marked Wrong, Seems Legal: Software Bug? [duplicate]

The included screenshot shows an attempted Sudoku move. The computer is marking it incorrect. There is no other 7 in the row, column, or 3x3 cell. What gives?
9
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2answers
557 views

Another Colombian Sudoku

Solve the Sudoku on the left, where the usual rules apply. The dots outside the board on the right indicate how many cells in the corresponding column or row of that board contain precisely the same ...
3
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3answers
106 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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1answer
133 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?
3
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2answers
136 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 ...
2
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1answer
147 views

What can be the next move without guessing in this almost solved Sudoku puzzle?

I am currently stuck at this puzzle where I can't think of the next move without guessing it. I was surprised to be in this situation after solving ~70-80% of the puzzle. I thought for all possible ...
3
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2answers
114 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 ...
4
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1answer
106 views

Sudokus and combinatorics

Considering your suggestions, I have redrawn the 12 X 12 Sudoku so that the twelve rectangles are now visible. The question remains the same: Can someone construct a 12 X 12 Sudoku with the following ...
7
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6answers
1k views

What next step can I take in solving this sudoku?

There are lots of pairs and I don't want to assume any values.
3
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0answers
159 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?
13
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1answer
357 views

Sandwich Sudoku: First 12 digits of pi

Sandwich Sudoku, or "Between 1 and 9 Sudoku", is a variant of Sudoku. A YouTube channel introduced this variation. Rules: Standard Sudoku rules. Place numbers from 1 to 9 in every row, column, ...
3
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5answers
450 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 ...
4
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3answers
408 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
89 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 ...
2
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0answers
78 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
174 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
419 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
206 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
367 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 ...
-5
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2answers
154 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
176 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 ...
1
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1answer
300 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
183 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
117 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
3k 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
326 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
votes
4answers
1k 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?...
0
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0answers
92 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
305 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
1k 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
votes
1answer
301 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
votes
2answers
182 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
4k 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
214 views

A Quick Sudoklu

Across ...
3
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1answer
165 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
527 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
269 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
votes
2answers
195 views

Stuck on this Sudoku!

I have tried every trick I can think of... where am I going wrong?
4
votes
1answer
237 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 ...
1
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2answers
187 views

How do I proceed with this Sudoku puzzle?

Pairing elimination is done. What's next?
1
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1answer
284 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 ...
1
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2answers
3k 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
84 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
votes
1answer
354 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
3k 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 ...