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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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69
votes
1answer
4k views

This new puzzle type needs a name

I believe I have invented a new type of puzzle... What is its name? Colour-blind-friendly version available here. Begin by solving the 16x16 sudoku; each of the digits 1-16 must appear exactly ...
23
votes
4answers
958 views

Another new puzzle type needs a name

For an example of how this type of puzzle works, see here... I believe I have invented another new type of puzzle... What is its name? Colour-blind-friendly version available here. Begin by ...
11
votes
2answers
467 views

Compoundoku wants BIG

Rules of Compoundoku: Solve both left and right Sudokus. In addition, the board below them is the Compound Board of both Sudokus. Each number on the Compound Board should tell either: (1) ...
23
votes
2answers
1k views

Introducing: Compoundoku!

Rules of Compoundoku: Solve both left and right Sudokus. In addition, the board below them is the Compound Board of both Sudokus. Each number on the Compound Board should tell either: (1) ...
8
votes
1answer
221 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 ...
2
votes
1answer
120 views

Sudoku - can’t get any further

What technique am I missing here? I have try all the usual naked pairs etc.
3
votes
1answer
116 views

What is the technique I should use now to go ahead?

This is a partially filled sudoku from the Sudoku Expert app. I thought I learnt all tricks and techniques. But clearly there is something I don't know about.
9
votes
3answers
684 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 ...
3
votes
2answers
795 views

Unsolvable sudoku net with maximum blocks

Definitions For a $9\times9$ grid $G$ (not necessarily respecting sudoku rules), a subset of cells $S$ is defined to be sudoku-friendly if the values in $S$ do not contradict the rules of sudoku. ...
36
votes
6answers
1k views

Sudoku embedded in a Kakuro

In addition to standard Kakuro rules, the grey shaded cells must form a valid Sudoku solution. One sum in this puzzle has been corrected from 28 to 23. Fortunately, it was in a location that nobody ...
3
votes
4answers
379 views

Help with a sudoku puzzle

I would really appreciate some help because I spent more than hours finding another number. It is supposed to be a very hard one but I started well and according to the key, my numbers are correct. Do ...
4
votes
2answers
135 views

Sudoku, unclear next logical step?

Solved up until here, I took the sudoku through an online solver and it seemed to use a guess and check strategy? Is that the only way of getting the solution or am I missing something?
5
votes
1answer
139 views

All That Remains Sudoku

. 2 . | . 7 . | . . 9 . 9 8 | . . . | . . . 3 . . | 9 . . | . . . ---------+---------+-------- 2 . 7 | . . . | . . . . 1 5 | 7 . . | . . . . . . | 1 5 8 | . ...
8
votes
1answer
233 views

Whirlwind of the Square Sudoku Table

. . . | . . . | . . . 6 . . | . . 1 | . 2 . . . . | . . . | . . . ---------+---------+-------- . . 7 | . . . | . . . . . . | . . . | . . . . . . | . . . | . ...
13
votes
1answer
186 views

Queens of the Square Sudoku Table

. 6 . | 8 . 3 | . 7 . . . 1 | . . . | . 6 9 7 . . | . . . | . . 5 ---------+---------+-------- . . . | 9 . . | . 1 . . . . | . . . | . . 4 . . 5 | . 1 . | . ...
6
votes
1answer
258 views

Knights of the Square Sudoku Table

8 . . | . . . | . . 6 . . 4 | . . . | . . . . . . | . . . | 9 1 . ---------+---------+-------- . . . | . 2 . | . . . . . 9 | 3 . . | . . . . . . | . . . | . ...
4
votes
1answer
138 views

What technique I should use now? [closed]

I am stuck here. I don't want solution for this, I just want to know the name of technique which will be used here to go ahead.
7
votes
2answers
170 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
votes
3answers
177 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?
10
votes
2answers
578 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
votes
3answers
110 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
votes
1answer
137 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
votes
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
votes
1answer
153 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
votes
2answers
116 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
votes
1answer
111 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
votes
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
votes
0answers
172 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
votes
1answer
384 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
votes
5answers
498 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
votes
3answers
465 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
votes
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 "...
11
votes
1answer
3k 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?
2
votes
0answers
92 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
votes
1answer
175 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 ...
3
votes
0answers
90 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 ...
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.), ...
10
votes
1answer
496 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
votes
2answers
213 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
votes
2answers
372 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
votes
2answers
179 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
votes
2answers
165 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 ...
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! ...
1
vote
1answer
309 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
votes
2answers
195 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
votes
1answer
134 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
votes
1answer
94 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 ...
1
vote
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?
8
votes
2answers
329 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 ...
25
votes
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.