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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8
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1answer
149 views

Sliced sudoku: rearrange the tiles and then solve it

Rearrange the tiles without rotating nor flipping them to form a $9 \times 9$ sudoku. Then solve the sudoku according to the standard rules. Credits: the sudoku is one of the twelve schemas freely ...
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1answer
818 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
637 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 ...
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1answer
243 views

Whirlwind of the Square Sudoku Table

. . . | . . . | . . . 6 . . | . . 1 | . 2 . . . . | . . . | . . . ---------+---------+-------- . . 7 | . . . | . . . . . . | . . . | . . . . . . | . . . | . ...
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2answers
363 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
1k 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
180 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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1answer
717 views

How can this puzzle be solved without guessing?

This puzzle was given to my 8 year old from the school. My child was struggling, so I gave it a bash, but was unable. I do sudoku regularly so know most methods of solving. I gave it to my husband and ...
7
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1answer
733 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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2answers
198 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
255 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
283 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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1answer
959 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 ...
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5answers
507 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; ...
7
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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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2answers
225 views

Puzzle of the day, Frame Sudoku

The rules are the same as the classic Sudoku, but the numbers outside the grid are the sum of the first three digits placed closest to that row or column
7
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1answer
389 views

Knights of the Square Sudoku Table

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

Sudoku and guessing : theory?

It has been proven that the minimum number of givens for a uniquely solvable classic 9x9 sudoku is 17. The usual solving method followed by people is : Fill all the cells where you are sure there is ...
7
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1answer
870 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 ...
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2answers
6k 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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3answers
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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 "...
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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 ...
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6answers
423 views

Good resource for daily Sudoku Puzzles

I love solving puzzles, It keeps my brain active. Previously I used to solve newspaper Sudoku which were fairly easy. Then I solved some interesting puzzles in the ...
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2answers
308 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 ...
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1answer
333 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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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
6k 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, ...
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2answers
566 views

Multiplicative sudoku (don’t use computers please)

If I place all the numbers from 1 to 9 in a 3x3 grid and I add the products of each row and column, then what is the minimal and the maximal sum? For example, the sum is 450 on the picture above
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2answers
818 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. ...
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2answers
228 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 ...
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2answers
698 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
816 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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1answer
120 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 ...
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2answers
186 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 ...
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1answer
215 views

A Quick Sudoklu

Across ...
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1answer
155 views

Against the Grain, Salt to the Sea: Sudoku

Against the Grain, Grain of Salt, Salt to the Sea, Sea...badge? What Badge? Of course, guessing is not fun, right? Anyway, congratulations to anyone who get this! :D
5
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1answer
575 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
182 views

Just Another Sudoku for PSE

Crafted with love for PSE, <3
5
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1answer
274 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 ...
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1answer
152 views

All That Remains Sudoku

. 2 . | . 7 . | . . 9 . 9 8 | . . . | . . . 3 . . | 9 . . | . . . ---------+---------+-------- 2 . 7 | . . . | . . . . 1 5 | 7 . . | . . . . . . | 1 5 8 | . ...
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2answers
526 views

How to solve this Sudoku?

Here is the sudoku - I could think the following only. The top number box 3 coloumn wise should have some number - 6,7,3 (in some order). The box 3 column 2 -- 2,5,8 ( in some order), and box 3 ...
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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 ...
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2answers
260 views

What is the maximum number of numbers a sudoku can have and have more than one solution?

I was watching this video where he talked about how scientists found the minimum number of numbers a Sudoku can have and still have exactly one solution. This led me to think of the opposite - what is ...
4
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2answers
857 views

What should be used to solve the next step of this sudoku puzzle

How to solve the next step in this sudoku ? I tried X-wing, hidden pairs and many other popular techniques found here http://hodoku.sourceforge.net/en/tech_hidden.php
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3answers
511 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 ...
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4answers
350 views

Do there exist Graeco-Latin Square style puzzles?

Sudoku, KenKen, and Skyscrapers are three examples of Latin square puzzles. In all three, players are challenged to complete a Latin Square, a NxN grid (typically 9x9) in which the numbers 1-N appear ...
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2answers
3k views

Is a 'legit' Sudoku puzzle supposed to be symmetrical?

Or phrased differently, are non-symmetrical Sudoku puzzles considered legal?
4
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1answer
456 views

Sudoku: Stuck, Need hint to move forward

I have applied the techniques I know to eliminate possible candidates. I'm stuck at this stage now, any hints to move forward are appreciated. I found this puzzle in Microsoft sudoku Android app.
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4answers
954 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?