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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6
votes
1answer
128 views

Tiling three pears with three-pair hexominos

The 21 hexominos below are all those that can be made by joining three dominos together (i.e. they have a perfect matching with respect to the graph of their squares) and are not rectangles. The ...
0
votes
1answer
90 views

Does every validly posed Sudoku have at least one solution and if not what is the minimum number of givens for it to be unsolvable? [duplicate]

Does every validly posed Sudoku (doesn't break any Sudoku rules so only no duplicate 1 to 9 in rows, columns or square) have at least one solution, and if not, what is the minimum number of givens for ...
19
votes
1answer
640 views

Tapata (Tapa variation)

Rules: Shade some cells so that all shaded cell form one orthogonally connected area. Numbered cells are either tapa clue (represent the lengths of the shaded cell surrounding that clue) or pata clue ...
27
votes
2answers
3k views

Sudoku on a Mobius Strip

Well we've done sudoku on keyboards, so the next step is obviously putting a Sudoku on a Mobius strip... of course... I present, the world's very first MOBIUS SUDOKU: Now this sudoku is going to be a ...
9
votes
1answer
935 views

Strategies for Circuit Board Puzzle from NYT

The New York Times publishes a collection of variety puzzles each week, and new to the rotation recently is one called "Circuit Board". Here is an example of a puzzle (I added coordinates ...
3
votes
1answer
148 views

How many Hoshi (Star Sudoku) are possible?

A gifted Sudoku booklet's Hoshi are (almost? - I did only spot checks) all identical, except for number permutation and leads. An excuse for this would be if there were only one legit Hoshi. How many ...
2
votes
1answer
205 views

Mysterious Deaths, or is it just a well known attack?

Last week you were promoted to the position of Sergeant Head Detective of Australia, which basically means the best detective in Australia. Its January 2019, and you wake up ready for your new job. ...
17
votes
4answers
1k views

It's a LITS! And a... um...?

I've combined two of my favourite puzzle types - a LITS grid-deduction puzzle and a, er... a, um... you know, I could have sworn I wrote it down here somewhere! Click on the image for a resolution ...
15
votes
1answer
825 views

9x9 Vanilla Tapa

Rules of Tapa: Shade some cells so that all shaded cells form one orthogonally connected area. Clues cannot be shaded and represent the lengths of the shaded cell surrounding that clue. If there are ...
22
votes
2answers
2k views

Sudoku.... On your keyboard?

Tired of solving Sudokus on paper? Look no further! The solution is, literally, under your nose. Why use a 9x9 grid, when you can use your own QWERTY keyboard! RULES: Fill each row with the numbers ...
17
votes
2answers
2k views

Must any "hourglass" touching the hexagon, in a Sudoku Hoshi, contain the same number twice?

I think I found a law for Sudoku Hoshi (also called Star Sudoku) puzzles but since I did the proof more or less in my head, please check. In case you don't know the rules, I quote: Fill the grid so ...
14
votes
1answer
628 views

(Re-)Introducing KPK Puzzle!

Rules of KPK: Put the letter K or P on every empty cell. Clues outside the grid on the first row/column show how many letters ordered as "KPK" can be seen on the corresponding row or column....
7
votes
1answer
178 views

Japanese Streams - No Sudoku!

Two previous puzzles, were inspired by the recent Japanese Sums puzzle series at Grandmaster Puzzles. Both of the previous puzzles were integrated as Sudoku variants, but this puzzle is a bit purer, ...
8
votes
1answer
236 views

Japanese Streams Sudoku

TL;DR - it's a puzzle: In a previous puzzle, we presented a puzzle inspired by the recent Japanese Sums puzzle series at Grandmaster Puzzles which combined the Japanese sums cluing technique with a ...
16
votes
1answer
232 views

Japanese Odd Sum Sudoku

The Grandmaster Puzzles blog had a recent set of "Japanese sums" puzzles, and the mechanics of those puzzles gave me the idea for a Sudoku. It's not too hard, so I hope you enjoy! The Sudoku ...
5
votes
1answer
970 views

Can you make a puzzle that looks correct until the very last piece?

Lately I've been enjoying a little game called Flow Fit: Sudoku. It's basically sudoku meets jigsaw. You need to place the pieces into predetermined slots, and numbers cannot repeat in the same rows/...
17
votes
1answer
693 views

Slitherlink with a 4

Yesterday, I got my pen-pal to teach me the rules of Slitherlink. I had to use a translator to understand what she wrote though, and as a result I suspect I've misunderstood some of her points. I've ...
3
votes
1answer
146 views

Next move in The Times Sudoku #12583

I'm completely stuck on how to move on with this Sudoku - what's the next number? It's from The Times puzzles - number 12583 on 13/08/21
3
votes
1answer
237 views

Why can R1c3 not be a 4?

Take the following Killer Sudoku (from the app "Killer Sudoku" by Studio Goya LLC) I have been struggling with for the last few hours. "Penciled" numbers are my notes about which ...
3
votes
1answer
250 views

Is there a minimum number of clues that every sudoku puzzle has?

I've seen that the fewest clues on a Sudoku board has been proven to be 17 but I'm wondering if it's possible for every board to have some combination of 17 clues or, if not, if there is a proven ...
2
votes
2answers
193 views

What's the next logical step for this Kakuro? 2

I thought the clue might lie in the 26 column, but I listed all possibilities and can't eliminate any values: 8+4+6+7+1 9+1+6+7+3 8+1+6+9+2 8+4+2+9+3 Source: Puzzle Page app
10
votes
2answers
418 views

Nurikabe: An Inconvenient Twelve

This puzzle is a Nurikabe. I've been busy and haven't made my trademark puzzle in a couple of months, so consider this my comeback puzzle and my apology! Hopefully you enjoy. Rules of a Nurikabe (...
2
votes
1answer
81 views

What's the next logical step for this Kakuro?

The puzzle is small but frustrating. Here's what I've deduced so far: In the 36 row, there are two missing digits which sum to 9, these must be 1+8 so the remaining empty cells are 2,3,4 In the 36 ...
8
votes
1answer
255 views

Existence of index-uniform Hashi puzzles

On the left, we have a starting configuration for a game of Hashi, and on the right, its solution: That is to say, the goal is to make connections (planar, and traveling only in cardinal directions) ...
15
votes
2answers
846 views

Encrypted Pentopia

Rules of Pentopia: Place some pentominoes into the grid (not necessarily all of them) so that they do not touch each other, not even diagonally. Pentominoes cannot repeat in the grid; rotations and ...
3
votes
0answers
206 views

Mega-puzzle of many number puzzles: Nikoli Octathlon

This puzzle has been my Moby Dick of puzzles for so long. It's from MellowMelon's old puzzle site and is a Nikoli-based megapuzzle with eight sub-puzzles. I'm copying the puzzle image from there so as ...
25
votes
2answers
2k views

Encrypted Snake (Grid Puzzle)

Rules of Snake: Shade some cells to form a non-intersecting path which does not touch itself, not even diagonally. Black circles must lie on one end of the path. White circles must lie somewhere ...
15
votes
1answer
360 views

Sum-until-1 Fillomino: Odds, Fibonacci, and Pi

Fillomino rules (taken from Nikoli): Fill in all empty cells with numbers under the following rules. Divide all of the board into blocks. Fill each block with the same number horizontally or ...
15
votes
2answers
367 views

Sub Battle Sudoku

Please find below a variant Sudoku which incorporates elements of Star Battle. The Sudoku is a standard irregular Sudoku, and the clues outside the grid are sandwich clues: the sum of digits strictly ...
9
votes
1answer
465 views

Where's the path?

A person was shading several unit squares in a square grid, to create a path from the bottom left corner to the top right corner. The path stepped from each square to the next either horizontally or ...
14
votes
1answer
283 views

Mid-loop: Coming Soon

Rules of Mid-loop: Draw a single loop passing through all of the black dots. The loop may not branch off, intersect, or move diagonally. The loop cannot bend at the black dot. Each black dots denotes ...
10
votes
2answers
330 views

Trio Tapa: Introduction

Rules of Tapa (copied from here): Shade some cells of the grid. Shaded cells should form a single [orthogonally] connected group; no 2×2 square should be fully shaded. Some cells have clues in them. ...
14
votes
3answers
346 views

Cross ALL the Streams

This grid deduction puzzle is a hybrid of three puzzle types: Cross the Streams, Tapa and Star Battle; rules for each are summarized below. In this grid, every cell is to be shaded either red, blue, ...
17
votes
2answers
689 views

XV Sawtooth Sudoku

Please find below a variant Sudoku puzzle, based on a combinatorics problem I was having a look at. The timing is right, as I recently saw @BeastlyGerbil back in chat, and I know that user is a big ...
3
votes
1answer
621 views

A tough Word-Nurikabe puzzle

I came up with this Word Nurikabe Puzzle, which was NOT a part of the Puzzle Ramayan, the qualifiers for Indian Puzzle Championship. Rules Place the given words in the grids ‘islands’, so ...
2
votes
2answers
220 views

How to get started on this Slitherlink (No Swiss)?

This is a puzzle from Round 4 of WPF's Puzzle Grand Prix this year. It's a Slitherlink with the additional rule that "Every Swiss cross-shaped arrangement of five cells must contain at least one ...
7
votes
1answer
242 views

Toroidal Weaved Truncated Square Tiling Tapa

Rules of Toroidal Weaved Truncated Square Tiling Tapa: The grid wraps around horizontally and vertically and also is divided into several 1-cell and 3-cells tiles. Shade some tiles such that all ...
1
vote
1answer
257 views

Can Arrows puzzles have multiple solutions?

I am trying to make an Arrows puzzle, but I don't know if there are multiple solutions. For those who don't know, an Arrows puzzle starts with a grid of numbers (example from SE) surrounded by empty ...
3
votes
1answer
683 views

What's the next step for this Kakuro puzzle?

What's the next step for the below Kakuro puzzle? Source: Puzzle Page app
10
votes
1answer
183 views

3D Tapa - Count to Five

Rules of 3D Tapa: The grid is a 3-dimensional cubes, represented here by layers of cubes from top to bottom. Shade some cubes such that all shaded cubes form a single orthogonally (in 3-axis) ...
5
votes
1answer
472 views

The next steps for this Kakuro puzzle

What are the next steps for this Kakuro? I've solved most of it, but there is an area I'm stuck on. Source: Puzzle Page app
7
votes
1answer
322 views

"Puzzle Waffle"

A black man, tilting his head in satisfaction and checking it was about lunchtime, entered the Sphinx Café in downtown Washington D.C. on a Friday out of boredom with his usual lunch haunt and greeted ...
8
votes
2answers
482 views

A Sudoku With A Trick

Normal Sudoku rules apply in this puzzle. This is an incredibly difficult puzzle to solve and has a very clever and ingenious trick in it. I request solvers to show their work at different stages of ...
14
votes
1answer
720 views

Up like a rocket ship

This is a Palisade (or 6 Cells) puzzle. The rules are: Thicken some of the pentagons' sides so the thick borders outline regions of six pentagons apiece. Any pentagon with a number in it indicates ...
16
votes
1answer
360 views

A Dotless Kropki

Rules of Kropki: Each row and column contains one occurrence of each digit from one to the size of the grid. All pairs of orthogonally adjacent cells containing numbers with a 1:2 ratio are marked ...
3
votes
5answers
830 views

Can you fill the cells by integers? [duplicate]

Can you fill the cells with integers so that all the equalities must be true?
11
votes
1answer
255 views

Stostone - Aoi's Big Birthday

Rules of Stostone: Shade exactly one stone, an orthogonally-connected group of cells, in each region. No two stones in different regions are adjacent. If a number is in a region, it tells the size of ...
3
votes
1answer
203 views

Quadruped Mosaic

This is a visual puzzle (known as "mosaic" or "fill-a-pix") with the same rules as MineSweeper: This puzzle has exactly 100 x 100 cells. The grid is to be filled with colored and ...
5
votes
1answer
246 views

A brain[expletive] sudoku

This is a Sudoku that is also a Brainfuck program. The standard rules of Sudoku apply. The same symbol can not appear twice in the same row, column, or 3x3 box. The grid should also form a functioning ...
18
votes
1answer
580 views

Slitherknot (Double Slitherlink)

This is a variation on the classic Slitherlink Puzzle. However, instead of creating one loop, you must create 2 separate loops. The two loops can not share any edges, however they can cross or meet on ...

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