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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14
votes
1answer
658 views

Ripple Effect ... with Inequality Sign

I was making ripple effect but failed on uniqueness. That leads me to think of using inequality signs to fix the puzzle. Then, I'm wondering, what if, I make a new one with intentional inequality ...
4
votes
1answer
110 views

Cube Connect Challenges

Cube Connect is a Flow-like mobile puzzle game on the surface of a cube. Rules of Flow (which is simply Numberlink with colors instead of numbers; copied from Nikoli rules with small modification): ...
6
votes
1answer
165 views

Themed Boggle Grids

Inspired by this puzzle, I created (or discovered) these grids. Within each Boggle board is a set of words with a common theme. To make a word in Boggle, connect at least three letters horizontally, ...
9
votes
1answer
240 views

Double Choco: I love myself

Rules of Double Choco: (copied from here) Divide the grid into regions by drawing along some of the dotted lines. Each region should have one group of gray cells and one group of white cells; both of ...
13
votes
1answer
463 views

Pipelink: A Cat for jkittykitkat

Rules of Pipelink: Draw a loop through the centers of all cells. Two perpendicular line segments may intersect (cross) each other, but not turn at their intersection or otherwise overlap. Clues show ...
5
votes
3answers
307 views

Filling a grid with skinny trominoes which have arrows on their ends

Let's have a 10x10 square grid with 7 empty small squares. This grid is to be filled with skinny trominoes which have arrows at their ends (see figure 1). What is the maximum number of arrows which ...
15
votes
2answers
792 views

Imagine a Sudoku with Text-Only: A Gridless 6x6 Antiknight Antidouble Sudoku

Imagine the following Sudoku: Imagine the Sudoku has a 6x6 grid with standard boxes, 2 rows and 3 columns each; and standard digits, 1 to 6. Imagine it has an antiknight rule: identical digits cannot ...
6
votes
4answers
683 views

Train Tracks: is there a unique solution?

In the last year or so a puzzle has been appearing in 'The Guardian' (a UK newspaper). It looks like this: and the instructions are as follows: Lay tracks to enable the train to travel from village ...
17
votes
3answers
456 views

Oh no, my puzzles are corrupted! What should I do? :(

This morning, I made three small and easy puzzles to be posted today. However, when I come back from my lunch, all of my puzzles are corrupted! :( The first one is a standard Curve Data puzzle. ...
3
votes
2answers
266 views

It's kind-of like Minesweeper

Have you ever played "Minesweeper" or "Lights Out!" and wondered what it would be like to reverse the process? Me too! Say hello to a 10 by 10 grid that I like to call "Number ...
4
votes
1answer
704 views

A 4x4 grid of red?

How is this 4x4 grid of red, colored? The only hint I'll give is that
6
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3answers
428 views

Spin the letter-squares!

Spin the letter-squares! A 5x3 grid of letters, e.g., a b c d e f g h i j k l m n o can be rearranged by spinning either the 3x3 section centered at the second letter of the second row (in this case ...
3
votes
1answer
179 views

Let's settle our differences

Can you complete this grid and expose the existing relationships? There are no complex operations (e.g. no exponents, square roots, functions, etc), additionally the numbers are all natural numbers ...
3
votes
2answers
333 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 &...
8
votes
1answer
440 views

Can you reactivate a 4x4 Magic Square?

We've already removed the magic from a 3x3 magic square. Recently, one of our 4x4 magic squares was scrambled in an earthquake and I need your help to reactivate it's magic: Objective Your objective ...
3
votes
2answers
268 views

Fix this puzzle, please!

My students claim that this disconnect four puzzle (fill the grid with crosses and zeros, such that no four equal symbols appear in a row. Rows can be horizontal, vertical, or diagonal) does not have ...
6
votes
3answers
867 views

Help solving this sudoku?

I went up in difficulty on my Sudoku app (Enjoy Sudoku app on Android). I keep getting mostly through them; however, I keep getting stuck towards the end of the puzzle. An example is shown below. Can ...
8
votes
2answers
173 views

Orthogonal Sudokus

This a Sudoku puzzle created by Paul Vaderlind. Fill each cell with 2-digit numbers from 11 to 99 (without the digit 0) such that The first digits represent one regular Sudoku grid. The second digits ...
12
votes
1answer
261 views

KPK 2021 Leftover: Double Back (Little Killer)

Rules of Double Back: Draw a non-intersecting loop through the centers of all empty cells. The loop passes through each region exactly twice. These two puzzles are the leftover of KPK 2021. The ...
11
votes
2answers
781 views

Remove the magic from a 3x3 Magic Square

It's commonly stated that there is only one solution to the 3x3 magic square. This is simply because every variant found is simply a rotation, reflection or both of any other variant. Once such ...
8
votes
1answer
126 views

Trichain: Tetrachain

This is a Trichain puzzle. The rules of Trichain are as follows: Numbers must be white, and match the size of their white islands. Each white island can only contain at most one number. Some white ...
2
votes
0answers
89 views

Most leads in a "difficult" Sudoku

Since "difficult" is undefined, let me define it arbitrarily: A Sudoku is difficult if it can't be solved by only considering singles (naked or hidden), the most basic solving strategy. How ...
11
votes
2answers
501 views

Confectionery Crime Conundrum

Yesterday I received one of the strangest cases of my career as an I.S. PI (Insightful Sleuths Private Investigator). I was reclining in my chair, working on the latest crossword puzzle when I ...
11
votes
1answer
196 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
111 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
854 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 ...
31
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
1k 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
155 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
228 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
871 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 ...
23
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
636 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
182 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
245 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
270 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
975 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
709 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
147 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
2
votes
1answer
240 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
251 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
195 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
428 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
86 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 ...
7
votes
1answer
264 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) ...
14
votes
2answers
856 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
215 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 ...
24
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 ...

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