Questions tagged [grid-deduction]

Puzzles such as Sudoku or Kakuro, where the final state of a pre-existing grid must be deduced logically through clues placed within and/or around the grid. Use with the [logical-deduction] tag. For puzzles where you are given a list of clues which can be used to compose a grid to solve them logically, use the [logic-grid] tag instead.

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3 votes
1 answer
372 views

Is the 7-clue 6x6 Sudoku solvable?

So I was trying to find an 8-clue 6x6 Sudoku because I knew from this paper that only 8 clues were needed to create a 6x6 Sudoku with a unique solution. However, I have managed to find one with 7 ...
17 votes
1 answer
541 views

Invalid Jigsaw Sudoku Layout

The Jigsaw Sudoku Layout below is invalid (no Latin Squares exist for it). Why? Please find a short, yet complete, explanation (no computations involved). ...
8 votes
1 answer
453 views

Light Up (Akari), but on a real projective plane!

This is a Light Up (aka Akari) puzzle, except it is on what is called a real projective plane. A real projective plane is, simply put, just a Möbius strip with a single edge except for the fact that ...
2 votes
1 answer
141 views

What can I deduce next about this daily Light Up (Akari) puzzle? (Feb. 22, 2024, 7x7 Hard)

So yesterday, I was searching for online logical deduction puzzles when I came across this website called Brain Bashers which is a site filled with many different types of puzzles. I have been going ...
16 votes
2 answers
650 views

An unusually tricky Galaxy

Background I love Simon Tatham's Puzzles, especially for killing the odd few minutes. One of the available puzzles is Galaxies, based on Tentai Show. I can usually solve these in anywhere from 30 ...
52 votes
5 answers
5k views

Prime Number Snake

Place numbers 1 to 100 in the cells of the 10 x 10 board below in such a way that consecutive numbers occupy neighboring cells (either horizontally or vertically). Shaded cells should contain only ...
7 votes
1 answer
233 views

An Irregular Colombian Sudoku

Solve the Irregular Sudoku below (by Xavier Castillo), where the usual rules apply. The dots outside the board on top indicate how many cells in the corresponding column or row of that board contain ...
17 votes
1 answer
917 views

Mercury in Centigrade

This is part 55 of the puzzle series Around the World in Many Days. Each part is solvable on its own. Dear Puzzling, This is a non-consecutive thermo sudoku. Fill the grid so that each row, column ...
2 votes
2 answers
164 views

What can I next logically deduce in Day 62 of the Minesweeper Advent Calendar? (Fake 3D)

So I have gotten back into playing the Minesweeper Advent Calendars on heptaveegesimal.com, and recently came across the 2023 Minesweeper Advent Calendar. I am currently trying to beat Day 62, which I ...
12 votes
1 answer
2k views

Add rules to Minesweeper until you can start with nothing

Think of classic Minesweeper game, with the following list of restrictions on the placement of mines: C (Connected): All mines are connected via 8-way neighborhood (orthogonal and diagonal). Q (Quad):...
5 votes
1 answer
190 views

The Minesweeper Puzzle That Might Stump People

I thought this might be a different kind of puzzle. This is a game of Minesweeper that I played earlier today. All standard rules apply. For those who don't know, the number inside of each cell ...
3 votes
1 answer
197 views

Impossible pattern in slitherlink

The puzzle here is to analyze the following Slitherlink configuration and show that it is impossible. ...
1 vote
2 answers
289 views

Sudoku-net pseudo-solvable with minimum blocks

A sudoku net is defined here. A sudoku net is defined as 'pseudo-solvable' if we can deduce at least two valid 'not unique' solutions. friendly sudoku is defined here What is the sudoku net with ...
9 votes
2 answers
432 views

Unchained Again

This is part 53 of the puzzle series Around the World in Many Days. Each part is solvable on its own. Dear Puzzling, The black and white circles in this grid form a Masyu puzzle. Draw one continues ...
7 votes
3 answers
1k views

Continue a hard Loopy/Slitherlink puzzle without brute-force

This is a classic Slitherlink puzzle from Simon Tatham's Portable Puzzle puzzle collection. I was stuck at the position shown for quite a while until I found a way to continue by logical deduction. I ...
7 votes
2 answers
468 views

A Colombian Jigsaw Sudoku

This is a Colombian Jigsaw Sudoku where the usual rules apply, but with irregular boxes. The dots in the right-hand scheme indicate how many of the numbers in a particular row or column are correctly ...
12 votes
1 answer
468 views

Aquatic Giants – Heyawake / Marching Bands

This is part 52 of the puzzle series Around the World in Many Days. Each part is solvable on its own. “One, two, three, four, five, I love marine wildlife.” – unknown Dear Puzzling, The grid on the ...
11 votes
3 answers
1k 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 votes
1 answer
589 views

Hardcore Lighting - Excalidraw

Each yellow cell is a light that shines in exactly one direction, horizontally, vertically, or diagonally, endlessly, and goes through any block as long as the block is not a wall. Black cells do not ...
4 votes
1 answer
280 views

27 Directional Lights Celebrate 2024

Let us celebrate the start of 2024! (1 month late...) Direct each light (yellow) such that all unlit squares (white) are lit. Walls (black) block light from going through. Some clarifications of the ...
3 votes
1 answer
142 views

How do I transcribe a Kakuro into a Google Sheets?

As other questions of mine mentioned, I have been slowly working through some PDF puzzle books. I will shortly come up on Kakuro puzzles. Here is an example from the Wikipedia article: The parts ...
4 votes
1 answer
367 views

Creeper Lighting

There are two sets of similar but separate puzzles here; the white puzzle (with white cells) and the black puzzle (with black cells). Each puzzle is solved independently. Each number is a "...
11 votes
1 answer
411 views

One more Colombian Sudoku

Here is one more Colombia Sudoku devised by Xavier Castillo. The usual sudoku rules apply. The dots outside the board above indicate how many cells in the corresponding column or row of that board ...
16 votes
1 answer
729 views

Nurikabe: Back to basics

Rules of Nurikabe: Shade some cells in the grid. Each area of unshaded cells must contain exactly one number, which indicates the size of that area. Two unshaded areas may not share an edge, but they ...
-1 votes
1 answer
151 views

Minesweeper Queens

Based off of: Ken Duisenberg's Puzzle of the Week Oct. 15, 2003: Minesweeper Queens For the puzzle, in the given diagram, the numbered squares are empty, from which the given mines can be attacked by ...
1 vote
1 answer
252 views

What‘s the next step to solve this 10x10 nonogram?

I got stuck on this nonogram (picross) from the game “Murder by Numbers”: What is the next step from here?
13 votes
2 answers
407 views

Heyacrazy: Careening

This is a Heyacrazy puzzle, designed at request of testsolvers of previous puzzles who wanted to see how longer diagonals would work. Rules of Heyacrazy: Shade some cells of the grid. Shaded cells ...
2 votes
2 answers
728 views

On solving the minimally clued 8x8 Sudoku

So I have been doing research on the minimal amount of numbers needed to create an 8x8, and found this paper which went over the minimum amount of clues needed for a sudoku to have a unique solution ...
26 votes
1 answer
1k views

Orange on Turquoise

This is part 50 of the puzzle series Around the World in Many Days. Each part is solvable on its own. Dear Puzzling, This is a Beaches puzzle (or tricolour Aquariums, if you prefer). Shade some cells ...
11 votes
1 answer
324 views

Towering Above – a jigsaw crossword

This is part 49 of the puzzle series Around the World in Many Days. Each part is solvable on its own. Dear Puzzling, This is a jigsaw crossword. Fill every row and column of the grid using the given ...
12 votes
2 answers
524 views

sums and differences in consecutive grid [closed]

Fill in each square of the grid with a number from $1$ to $16$, using each number exactly once. Numbers at the left or top give the largest sum of two numbers in that row or column. Numbers at the ...
14 votes
1 answer
269 views

! ! ! HNY 2024 ! !?

The following puzzle is a typical Sudoku 12 x 12 (1-9, a, b, c), but with an added twist. In addition to the standard rules, each colored box must also contain unique digits; no repetition is allowed ...
4 votes
3 answers
482 views

Impasse with this Sudoku puzzle

This was an advanced puzzle, and I managed to take it as far as possible. Now, I am stuck. I have tried many advanced patterns to no avail. I could use some pointers. It's from an IOS app called &...
3 votes
1 answer
90 views

Help with nearly finished expert sudoku

I just started with Sudoku and I jumped directly to a difficult level. I have a hint but don't want to use it. Please provide logic with your answer.
7 votes
1 answer
293 views

Next Sudoku Number

Here is a sudoku puzzle coming from this magazine I found that B5 and B6 can only contain 6 and 7. 8 cannot be in B5 because D1 would be a 8 and neither B3 not C1 could be a 8. I thought it would help ...
13 votes
1 answer
467 views

Happy and joyful 2024!

Fill each empty cell of the board on the left with a digit between 1 and 9. Each box and each column and row must contain all digits. The dots outside the board on the right indicate how many cells in ...
15 votes
2 answers
1k views

Colombian Sudoku

Fill each empty cell of the board on the left with a digit between 1 and 6. Each column and row must contain all digits. The dots outside the board on the right indicate how many cells in the ...
17 votes
1 answer
620 views

Wreck Exploration

This is part 48 of the puzzle series Around the World in Many Days. Each part is solvable on its own. Dear Puzzling, The larger grid here is a Takuzu puzzle (also known as Binairo). Fill the grid ...
0 votes
0 answers
73 views

Heuristic function for estimating nurikabe puzzle state

I am trying to write a program for solving nurikabe puzzle. I need a method to approximately represent the state of the game in one number, to choose the best way for the algorithm to continue. I can'...
8 votes
3 answers
1k views

What technique can be used to solve this 6x6 sudoku?

Which Sudoku technique can be used to solve this? The screenshot is from the open source Sudoku app by SECUSO (Security Usability Society) for the Android platform.
-1 votes
2 answers
750 views

Another Yin-Yang puzzle

I saw someone post a ying-yang puzzle on here recently and I thought I might challenge people here with another one! Rules of Yin-Yang: Fill each empty cell with either a black circle or a white ...
14 votes
2 answers
857 views

PSE Advent Calendar 2023 (Day 20): Candles on the tree

This puzzle is part of the Puzzling Stack Exchange Advent Calendar 2023. The accepted answer to this question will be awarded a bounty worth 50 reputation.< Previous Door Next Door > Rules of ...
6 votes
1 answer
522 views

PSE Advent Calendar 2023 (Day 18): A holly jolly Hexologic

This puzzle is part of the Puzzling Stack Exchange Advent Calendar 2023. The accepted answer to this question will be awarded a bounty worth 50 reputation.< Previous Door Next Door > Rules: ...
3 votes
3 answers
820 views

How to solve Level 45 in Hexologic (easy mode)

For those who don't know how Hexologic works: You can place one, two or three dots in each blank space and the rows that end in arrows must all add up to the number in the arrow. Here is Level 45 (...
1 vote
1 answer
95 views

How do I do the Hard mode version of the 2nd bonus puzzle unlocked after beating level 45 in Hexologic?

In Hexologic, there are bonus levels that you can unlock after completing each 15 levels. (although it doesn't matter if it's on Easy or Hard mode) I have been able to complete all of the bonus levels ...
11 votes
2 answers
681 views

Turn Back the Clocks

This is part 45 of the puzzle series Around the World in Many Days. Each part is solvable on its own. Dear Puzzling, This is a Slitherlink puzzle. Draw a single continuous loop along grid lines that ...
18 votes
1 answer
815 views

PSE Advent Calendar 2023 (Day 11): Divide the cookies and milk

This puzzle is part of the Puzzling Stack Exchange Advent Calendar 2023. The accepted answer to this question will be awarded a bounty worth 50 reputation.< Previous Door Next Door > Santa’s ...
16 votes
2 answers
465 views

Another type of Sudoku puzzle

I just found a weird-looking sudoku I left years ago in my basement: I think there was a specific name for this type of puzzle, but I forgot to write it down and now I can't remember it! The only ...
18 votes
2 answers
763 views

PSE Advent Calendar 2023 (Day 9): The Peppermint Twist

This puzzle is part of the Puzzling Stack Exchange Advent Calendar 2023. The accepted answer to this question will be awarded a bounty worth 50 reputation.< Previous Door Next Door > This puzzle ...
11 votes
1 answer
241 views

Quadritaisho: The sports bet

My friend from America was going to watch a game and wanted to bet I couldn't guess where he was going. The answer lies in the Quadritaisho puzzle below. Can you help me find out where he's going to ...

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