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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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11
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1answer
350 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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3answers
2k views

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: ...
11
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2answers
2k views

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 ...
10
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1answer
323 views

What am I telling to you?

For my first question here, let's start cool with a little sketch. No, it's no hard brainstorming, no, it's not a revolution, yes, I had to start with something :)
10
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1answer
279 views

RELATIONS: Introducing the Sudokross

Behold my sudokross!                           Similar to sudoku, the objective is to fill every row and every column with the ...
10
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1answer
394 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. ...
10
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1answer
1k views

Sudoku with chess queen rules

This is a unique sudoku. With Rules : Common sudoku rules apply. Numbers 1,2,3 have an additional rule, they are also chess queens. If all others numbers removed, the 1s do not attack each other ...
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3answers
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What is the maximum number of empty 3x3 blocks a proper Sudoku can have?

It is possible to have a proper Sudoku with one empty block (consisting of 3x3 cells). The trivial (and very boring) example would be a puzzle where all other cells are given. It's impossible to have ...
9
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2answers
473 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
536 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 ...
9
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2answers
364 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 ...
9
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1answer
610 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
528 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 ...
8
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2answers
758 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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2answers
2k views

Can you solve the 7x7 (sudoku-ish) centered sums puzzle

I have come across this puzzle a few times in competitions and rally's, and it has troubled me because I cannot seem to find a good approach to solving it, either programmatically or numerically. And ...
8
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1answer
261 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: ...
8
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1answer
1k views

Christmas Sudoku

CHRISTMAS IS COMING!!! And to celebrate, here is a Christmas related sudoku: *A friend gave this to me and it took a long time for me to solve it. Thaks to @GentlePurpleRain for providing an updated ...
8
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3answers
477 views

Revenge of the 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 relevant order. The solutions to the ...
8
votes
1answer
368 views

How to deal with conjugate-pair pseudocycles when solving Sudoku

In single-solution regular Sudoku puzzles, sometimes you may encounter a combination of possible cell solutions such as: {2,7} in A1 and A7 (same row) {2,7} in A7 and B8 (same box) {2,7} in B8 and E8 ...
8
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1answer
758 views

Algebra Sudoku: Dozens

Alas, the grid deduction fortnightly is over, but my love for the genre remains the same - i.e. very high. So, here is another grid deduction puzzle. An algebra sudoku! I think the rules are fairly ...
8
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1answer
608 views

How to avoid getting “stuck” while generating sudoku puzzles?

I understand the basic method of generating sudoku puzzles, which is: Put a random number in the current square. If the puzzle is still valid, go to the next square. Otherwise, stay on the same ...
8
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2answers
322 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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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.
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2answers
955 views

Non brute-force Sudoku

The mypuzzle.org site (Difficulty = Hard, Date = 2016-07-12) has the following Sudoku puzzle. I filled in a three easy cells (in square brackets) but then got stuck. Aside from brute force, is there a ...
7
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1answer
173 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 ...
7
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2answers
179 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 ...
7
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2answers
252 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 ...
7
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1answer
249 views

Introducing: Sudoku-Janpu

This is an entry into the 29th fortnightly topic challenge - Retrograde Analysis. Scenario: Alice and Bob were playing a game of Sudoku-Janpu. Alice: I win. Bob: (looking at the board) Oh man, not ...
7
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2answers
643 views

What is the fewest number of clues on a rotationally symmetrical sudoku grid with a unique solution?

It is known that the minimum number of clues a sudoku must have to have a unique solution is 17. But on every website I've seen for them, I haven't found any that are rotationally symmetrical. I once ...
7
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1answer
410 views

Skeleton sudoku, the second

I've already set one skeleton Sudoku. Here's a rather harder one. (Nonetheless, it should be within the realms of what can be done by hand; I solved it manually myself to verify that there was only ...
7
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1answer
871 views

Solve this Subtraction sudoku!

This is subtraction sudoku. The rules are basically the same as common Sudoku, but with a few additions. In the row, the number in the orange box is the difference when its left side (sum of 3 ...
7
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5answers
490 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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2answers
3k views

Minimum steps to verify a Sudoku solution

When checking if a 9x9 Sudoku solution is valid in the absence of an answer key it may not be necessary to check every row, column and 3x3 box. What is the minimum number of items (rows, columns, or ...
7
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1answer
708 views

How do I necessitate the use of the X-Wing pattern during Sudoku creation?

I want to create a Sudoku puzzle, and I want it to be of moderate difficulty. There's a specific pattern I want to include, called the X-Wing pattern: This occurs when two numbers form locked ...
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 "...
6
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3answers
1k views

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 start looking over the ...
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2answers
302 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 ...
6
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1answer
297 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 ...
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2answers
5k 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
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?...
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4answers
5k views

Special 5x5 Sudoku-like table

This is a special 5x5 Sudoku-like table. Each row, column, and diagonal contains digits from 1 to 5 (including diagonals obtained by wrapping around the edges). To filter duplicates (by rotation, ...
5
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2answers
894 views

Largest cages Killer Sudoku

Task 1: Find the maximum value of $n$ for which it is possible to create a regular uniquely-solvable Killer Sudoku (9x9) such that every cage has atleast $n$ cells in it. Rules for killer sudoku ...
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2answers
791 views

Special Sudoku, with windows pattern

Solve this Sudoku, with rules : Every blue square means, it is the left-top of a 3x3 block with each numbers [1 to 9] appearing only once there. There is only one unique solution. Check the example. ...
5
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2answers
203 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 ...
5
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2answers
547 views

Sudoku difference between x wing and double pair

Double Pairs and X Wing are listed as different techniques here (former is a medium and later a master technique). The only difference I can see is double pairs are restricted to two neighbor blocks ...
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3answers
696 views

Sudoku Puzzle, What's My Next Move and Why?

I currently have a sudoku puzzle that looks like this: ...
5
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2answers
174 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 ...
5
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1answer
213 views

A Quick Sudoklu

Across ...
5
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1answer
492 views

What will be the last Sudoku number to be filled?

When I am completing a Sudoku puzzle, there are always two last numbers to fill. Maybe it is just my puzzle solving approach or maybe it is inherent to Sudoku. I got wondering, would everyone who ...
5
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1answer
263 views

An EMIRP Game/ Puzzle for Prime enthusiasts

As most math enthusiasts know, EMIRPs are Prime Numbers which are also prime numbers when reversed. Like 17 which when reversed to 71 is also a prime number. Here is a Game or Puzzle based on 5 ...