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.

Filter by
Sorted by
Tagged with
73
votes
1answer
2k views

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!...
64
votes
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 ...
58
votes
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 ...
51
votes
4answers
43k views

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 ...
49
votes
11answers
57k views

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 ...
47
votes
1answer
1k views

Self-referential Sudoku

I built this a while back but never had a good forum for it; this seems like the perfect spot to turn it loose. This is a 'traditional' Sudoku; cells are filled with numbers from 1 through 9, and all ...
46
votes
2answers
2k views

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 ...
43
votes
4answers
5k views

Who am I??? Wait, isn't this a sudoku?

Jmw jrr qtlf tv ee M6SXr rro tr kz r tyr. Can you find out who I am? Hint 1: Hint 2:
43
votes
9answers
4k views

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 ...
43
votes
1answer
2k views

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 - ...
35
votes
11answers
4k views

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 ...
32
votes
3answers
3k views

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 ...
31
votes
6answers
18k views

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 ...
27
votes
2answers
821 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. ...
26
votes
2answers
1k views

Can you solve my Chess Sudoku puzzles?

Rules Normal Sudoku rules apply except that instead of 9s you must place chess pieces. A puzzle can mix chess pieces, and in principle any piece may be used - although the rest of the constraints ...
25
votes
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 ...
24
votes
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.
23
votes
1answer
446 views

Sudoku as Poetry: A Tag-Fusion Masterpiece

This is an entry in the 19th fortnightly topic challenge: Unconventional Tag Fusion. I wrote some poetry for you, but it's hidden within this sudoku. Solve the puzzle and find the poem. For those ...
23
votes
2answers
788 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 ...
21
votes
4answers
33k views

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, ...
20
votes
3answers
1k views

Introducing Domidoku!

Come one, come all! Come see the new type of logic puzzle, the Domidoku! Here's a sample for all to try! The process is simple! First you solve the Sudoku and then you solve the Dominosa! ...
19
votes
6answers
2k views

The Unfinished Puzzle Section

Simply complete the sudoku and crossword, happy puzzling. Across 1. Achieved acclaim by being knowledgable about strange apron (3, 6) Down 2. Explode asteroid five to refrain from inactivity or ...
18
votes
2answers
3k views

Why does generating a Sudoku work in lines, but not in a random pattern?

So, I'll preface this by saying that I am not 100% whether this fits better here or on SO. That said: I've been trying to generate Sudokus using a backtracking algorithm to fill in the whole thing. ...
17
votes
3answers
1k 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;...
17
votes
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 ...
17
votes
3answers
903 views

Single solved state for Sudoku Pyraminx

(Not sure if this is the correct stackexchange, but I think it is.) I recently bought 10 QJ Pyraminxes with an ambitious idea for a mod in my head. After just the first step of modding I realized it ...
16
votes
4answers
2k views

When Sudoku met Ratio

Continuing on from my previous sudoku... I found an old piece of paper with a sudoku solution on it and vaguely remember solving it. This is unlike a simple solution however. You get no starting ...
16
votes
2answers
1k views

Maximum Sudoku Puzzle

As most of you know, there is no Sudoku problem that has less than 17 number of starting clues with one unique solution. Imagine there is a sudoku problem that has $n$ number of starting clues with ...
16
votes
2answers
908 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. ...
15
votes
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.), ...
15
votes
3answers
1k views

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 ...
15
votes
1answer
1k views

Sum in A Sudoku

Color Blind version: Here's a sudoku puzzle with a twist! The numbers given in the squares are actually the sum of the numbers in that region. For example: 18= Sum of the numbers in the 4 yellow ...
15
votes
2answers
659 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 ...
13
votes
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 ...
13
votes
2answers
921 views

Devising a sudoku where the rows are the moves for a draw in tic tac toe

The task is to construct a sudoku whose rows (or columns) are the moves for a game in tic tac toe where the game ends in a draw. Here are some clarifications and constraints which should limit ...
13
votes
3answers
793 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, ...
13
votes
2answers
538 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
votes
2answers
1k views

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 ...
12
votes
2answers
778 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 ...
12
votes
2answers
2k views

Magic Squares in Sudoku Grids

A 3x3 magic square is a 3x3 grid containing the numbers 1-9 once each, and in which every row, column, and diagonal sums to 15: 294 753 618 And I presume we all ...
11
votes
2answers
742 views

Historical figure sudoku

This sudoku hides a famous person from the past. A solution will be accepted if the sudoku is solved (with steps to solve). The letters used are: abceloprt (in alphabetical order). PS. ...
11
votes
3answers
2k views

Creating a solved 9x9 Sudoku based on certain rules

The question: A rectangular fence is a set of 4 cells on a solved sudoku grid with co-ordinates $(i,j)$, $(m,j)$, $(m,n)$ and $(i,n)$. You can visualize this as the 4 corners of a rectangle. ...
11
votes
2answers
750 views

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 ...
11
votes
1answer
2k 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?
11
votes
1answer
3k 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 ...
11
votes
2answers
2k 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 "...
11
votes
2answers
6k 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: <...
11
votes
1answer
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?
11
votes
1answer
447 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 ...
11
votes
1answer
333 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-...