# 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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### Happy 2017 Sudoku

This is a simple Sudoku. The only thing different from a regular sudoku are the symbols used: HAPY2017*. The snowflakes (a.k.a. asterisk) are like any other character. Wishing you a Happy New Year ...
9k views

### Removing numbers from a full sudoku puzzle to create one with a unique solution

What is a simple and efficient way of removing numbers from a full sudoku puzzle to create one with a single unique solution? I have already figured out how to generate sudoku grids, like this one: <...
491 views

### Setka - Complete grid using clues and sudoku-style logic; Theme - Halftime

This is a Setka puzzle; you can find more (along with a more detailed explanation of the rules) at our website, linked from our profile. How to play Setka, the short version: Answer each clue using ...
568 views

### An experimental sudoku

(Here is an experimental Sudoku created by me, however, the "box" constraint is not originally mine, but it'd be fun to try out this constraint.) Rules: Normal Sudoku rules apply. ...
2k views

### Nested sudoku in entrance exam

My university set this question in 2013's entrance exam. Also the red boxes include from 1 to 9. What's the solution for this sudoku?
518 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 ...
797 views

### Help me to decorate my Christmas tree

Help me to decorate my Christmas tree with garlands of 7 bulbs. I want to fill in all the blank bulbs with numbers 1 to 7, so that each garland contains 7 different numbers. To make the tree more ...
500 views

### A Difficult Wacky Sudoku - SS#8

An entry in Fortnightly Topic Challenge #47: "Wacky Sudokus" Other puzzles in this series Welcome to the eighth puzzle in this series! For more information about the series, see the first ...
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: ...
421 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-...
2k 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 ...
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 ...
325 views

### Sudoku… with 10 digits? SS#6

An entry in Fortnightly Topic Challenge #47: "Wacky Sudokus" Other puzzles in this series Welcome to the sixth puzzle in this series! For more information about the series, see the first ...
278 views

### Less than 6 Sudoku

In the following sudoku the numbers on the borders indicate the first number less than 6 seen in that row/column. So for example, the 4 at the bottom means that the first number less than 6 seen from ...
913 views

### Calculation Sudoku

Here is a new quiz from my daily quiz calendar. I'm trying to find a way to solve it. The numbers 1-6 should be filled in. And like a sudoku, each row and each column should contain each number ...
768 views

### A Family Reunion

Names have been changed to preserve anonymity A group of 25 people, A to Y, arrived at Z's door to celebrate the family reunion. They each had something to show off. Z: I know you're all excited ...
631 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 ...
332 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 :)
412 views

### 1, 2, 3… Trinary!!! (SS#2)

An entry in Fortnightly Topic Challenge #47: "Wacky Sudokus" Other puzzles in this series Welcome to the second puzzle in this suduko series! For more information about the series, see the ...
324 views

### RELATIONS: Introducing the Sudokross

Behold my sudokross!                           Similar to sudoku, the objective is to fill every row and every column with the ...
719 views

### Knights of the Square Sudoku Table

8 . . | . . . | . . 6 . . 4 | . . . | . . . . . . | . . . | 9 1 . ---------+---------+-------- . . . | . 2 . | . . . . . 9 | 3 . . | . . . . . . | . . . | . ...
318 views

### No Numbers Sudoku: The Ball of Queens

Those are all of the numbers you need. No, I did not forget any. Normal sudoku rules apply. All numbers, except for 1's and 9's, are queens with respect to themselves. E.g. 2's have the queen's ...
2k views

### Sudoku medium difficulty help

I keep getting stuck on the NY Times Sudoku medium difficulty puzzles. I go through one number at a time and narrow down large box where that number can only be in two spaces. When I finish the nines ...
575 views

### How to see why single candidates are obviously correct?

I am trying to understand something that should be simple. I have a "easy" puzzle here, and immediately found where 8 should be in the middle box. But in various Sudoku Apps, they show &...
1k views

### Sudoku Help: Hard

I am unable to finish this Sudoku. All numbers are verified by the app. I'm sure there must be a way to solve this without guessing. Even an online tool couldn't tell me a next number.
3k views

### 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 ...
678 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 ...
332 views

### A 7x7 Suguru - SS#9

An entry in Fortnightly Topic Challenge #47: "Wacky Sudokus" Other puzzles in this series Welcome to the ninth puzzle in this series! For more information about the series, see the first ...
488 views

### Sudoku with no grid and no numbers!!? - SS#12

An entry in Fortnightly Topic Challenge #47: "Wacky Sudokus" Other puzzles in this series Welcome to the twelfth puzzle in this series! For more information about the series, see the first ...
514 views

### The Existence of Total False Sudoku

Is it possible to construct a valid 9x9 puzzle of Total False Sudoku? Total False Sudoku is a regular Sudoku puzzle where all given clue numbers are wrong. A valid puzzle is a puzzle that has only a ...
263 views

### A Fractal Sudoku - SS#13

An entry in Fortnightly Topic Challenge #47: "Wacky Sudokus" Other puzzles in this series Welcome to the penultimate puzzle in this series! For more information about the series, see the ...
401 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 ...
400 views

### Trivia… sudoku

An entry in Fortnightly Topic Challenge #49: Pub Quiz Camouflage Please do not search the answers online (hence the no-computers tag), otherwise it would be too simple to solve this puzzle. I tried ...
3k views

### A Sudoku with only four given digits and some more rules

This is one of the hardest Sudokus (and one of the best Sudokus) I have ever seen, with only 4 given digits. There are some more rules too: First, normal Sudoku rules apply here. Both the diagonals ...
296 views

### How much information can we get from a thermometer?

A fairly common Sudoku variant is so called "Thermometer" Sudoku. In this variant arrows with a rounded end (which look like a thermometer) are added to the grid, with the rule that the numbers on ...
865 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 ...
651 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 ...
163 views

### Sudoku: Episode 64 - Attack of the Clones

An 8x8 Sudoku where you technically only have to figure out 32 cells! Twice Half the cells, double the clues! Penpa Link Rules Normal Sudoku rules apply. Values are 1-8. Boxes are the 4x2 regions ...
167 views

### Shattered Webs - SS#3

An entry in Fortnightly Topic Challenge #47: "Wacky Sudokus" Other puzzles in this series Welcome to the third puzzle in this series! For more information about the series, see the first ...
207 views

### Puzzle of the day - three in one Sudoku?

A three in one sudoku. Have fun
606 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 ...
846 views

### Wanted: Sudoku data in CSV

I am a computer science student looking for unsolved sudoku games that are valid and available in a comma separated text file. Does such a prepared data set exist and where can I find such a data set? ...
1k 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 ...
334 views

### Q: Henry Goldman's Square of Digits

Jaap Scherphuis introduced The Arithmachinist by Henry Goldman in his post Goldman's Transformation Puzzle. In the book I found a curious figure on p.52. I wonder what it means. Could you let me know?...
961 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 ...
3k 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 ...
357 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: ...
2k 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 ...