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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Another four 3D masyu

This puzzle is inspired and descended from Brain-breaking 3D masyu Here the exact copy of rules, for convenience: This is a three-dimensional masyu puzzle.1 The five squares depict the layers of a $...
Alexey Birukov's user avatar
-4 votes
0 answers
85 views

Finding the Minimum-Step Path from (x,y) to (0, 0) with a Cumulative Sum of P [closed]

Imagine a 2D plane, where each point represents a position. Your mission is to trace a path from the origin (0,0) to an end point ...
Moix's user avatar
  • 9
7 votes
2 answers
680 views

A Difficult Colombian Sudoku?

This Colombian Sudoku is by Xavier Castillo. Usual Sudoku rules apply. Additionally, digits on each of the two diagonals must all be different. The dots outside the board above indicate how many cells ...
Bernardo Recamán Santos's user avatar
5 votes
0 answers
148 views

🐍 In the Loop 🐍

Follow the ouroboros down valleys and over mountains. Is it even going anywhere? Interactive Penpa+ version
DanDan面's user avatar
  • 711
5 votes
1 answer
378 views

Help with Star Battle puzzle

I made it through all the easy levels without ever having to consciously divide the whole grid into specific regions. I've seen that this is a common technique, but it confuses me even more when ...
gemmabomma's user avatar
12 votes
2 answers
321 views

A Crabby Sudoku

I present a *deep breath* Even-Odd TetroThermoDoku. From the back of the name to the front: Rules Sudoku: Fill each cell with a digit 1-9 such that no number repeats in any row, column, or 3x3 heavy-...
bobble's user avatar
  • 10.4k
13 votes
1 answer
554 views

Plumbing Issues

This is part 59 of the puzzle series Around the World in Many Days. Each part is solvable on its own. Dear Puzzling, This is a Pipes puzzle (also known as Net, FreeNet and NetWalk). Rotate some cells ...
Jafe's user avatar
  • 78k
17 votes
2 answers
1k views

A small board-puzzle

Place pieces (red) on the board, so every piece is adjacent to 4, 5 or 6 other pieces. I've created this puzzle myself playing around with cellular automatons.
Dromlius's user avatar
  • 175
20 votes
2 answers
898 views

Masyu: Four Colours

Draw four separate loops in the grid, one blue, one green, one grey and one red. Loops connect centres of cells horizontally and vertically and cannot cross over themselves or share any cell with each ...
Jafe's user avatar
  • 78k
3 votes
1 answer
409 views

Continue in 6x6 Towers puzzle

How can I continue with this Towers puzzle?
Alex Eh's user avatar
  • 31
10 votes
1 answer
1k views

Cover me, I'm going in!

This is part 58 of the puzzle series Around the World in Many Days. Each part is solvable on its own. Dear Puzzling, This is a diagramless checkerboard crossword. Empty cells are either blue or white;...
Jafe's user avatar
  • 78k
15 votes
1 answer
801 views

Riverboat Soufflé

This is part 57 of the puzzle series Around the World in Many Days. Each part is solvable on its own. Dear Puzzling, This is a bicolour Masyu puzzle. Draw two separate loops in the grid, one red and ...
Jafe's user avatar
  • 78k
1 vote
1 answer
162 views

What can I deduce about this daily Skyscrapers? (Mar. 18, 2024, 5x5 Easy)

So I have been using a site called Brain Bashers, which is a site filled with logical deduction puzzles, because I like trying to master different logical deduction puzzle types. I have finished the ...
CrSb0001's user avatar
  • 2,241
25 votes
3 answers
2k views

a few signposts

Assign an integer (1 through 16) to each cell so that: 16 is in the cell with the star; and each integer's arrow points to its successor (i.e. the next integer), though not necessarily in the ...
msh210's user avatar
  • 12.6k
6 votes
1 answer
237 views

Product = Sum Sudoku (Royal Statistical Society Christmas Quiz 2023)

Normal Sudoku rules for this grid size apply. The product of the numbers on each pink diagonal equals the sum of the numbers in the blue square. This puzzle is from the now closed contest at: https:/...
Will Octagon Gibson's user avatar
0 votes
0 answers
188 views

Continue with sudoku - how do I scan for next steps?

I filled some cells, but am stuck here. I cannot go any further. How do I advance? How would I scan the Sudoku to recognize next steps? I've taken the puzzle from https://play.google.com/store/apps/...
Abbas Baghirov's user avatar
6 votes
1 answer
165 views

A hard(?) 15-X puzzle

Below is the puzzle I came up with before writing Create a 15-X puzzle with a unique solution. Rules of the puzzle: A 6x6 grid is given. Fifteen cells are marked with an X. Use polystrips of lengths ...
Bubbler's user avatar
  • 14.1k
13 votes
2 answers
218 views

Create a 15-X puzzle with a unique solution

Background Last week, Brandan came up with a grid-deduction genre about filling a 6x6 grid with polystrips of lengths 1 through 8, using each length exactly once. A polystrip cannot bend twice in a ...
Bubbler's user avatar
  • 14.1k
3 votes
1 answer
208 views

Minimally clued 4x5 Hidato (4 clues)

Puzzle attribution: Me :) Background So as you might or might not know, I have been studying the minimum number of clues needed to force a unique solution in Hidato for variously sized boards. I ...
CrSb0001's user avatar
  • 2,241
6 votes
1 answer
176 views

5x5 Hidato with 4 single-digit clues

Goal of Hidato: Fill in a grid with a series of consecutive numbers that connect each other horizontally, vertically, or diagonally. Yesterday I posted New record for minimally clued 5x5 Hidato, ...
Bubbler's user avatar
  • 14.1k
9 votes
2 answers
273 views

How do I constrain a puzzle and keep a singular solution?

I am tinkering with a puzzle framework that has the following rules: In a 6x6 grid of squares, arrange 8 strips of connected squares such that there exists exactly one strip of every length (i.e. a ...
Brandan's user avatar
  • 93
11 votes
3 answers
601 views

New record for minimally clued 5x5 Hidato

CrSb0001 has been studying the minimum number of clues to force a unique solution in Hidato for variously sized boards. They came up with a 5x5 Hidato with 5 clues but it was found that it has ...
Bubbler's user avatar
  • 14.1k
4 votes
1 answer
212 views

Minimally clued 5x5 Hidato

Puzzle attribution: Me Goal of Hidato: Fill in a grid with a series of consecutive numbers that connect each other orthogonally or diagonally To get the green checkmark $\color{green}✓$: Solve the ...
CrSb0001's user avatar
  • 2,241
-4 votes
1 answer
103 views

Binary Grid Challenge and X & O Conundrum

You are given a 5x5 grid with some cells filled with either "X" or "O". Your goal is to fill the remaining cells with "X" or "O" following these rules: Each row ...
Aryan's user avatar
  • 109
13 votes
3 answers
1k views

What is the minimum amount of numbers needed to create a 4x4 Hidato with a unique solution?

Goal of Hidato: Fill in a grid with a series of consecutive numbers that connect each other horizontally, vertically, or diagonally. So I have been working on figuring out the minimum number of ...
CrSb0001's user avatar
  • 2,241
5 votes
1 answer
467 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 ...
CrSb0001's user avatar
  • 2,241
20 votes
1 answer
830 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). ...
JCO's user avatar
  • 440
9 votes
1 answer
484 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 ...
CrSb0001's user avatar
  • 2,241
17 votes
2 answers
724 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 ...
Matthew's user avatar
  • 377
7 votes
1 answer
301 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 ...
Bernardo Recamán Santos's user avatar
19 votes
1 answer
1k 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 ...
Jafe's user avatar
  • 78k
2 votes
1 answer
150 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 ...
CrSb0001's user avatar
  • 2,241
2 votes
2 answers
173 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 ...
CrSb0001's user avatar
  • 2,241
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):...
Bubbler's user avatar
  • 14.1k
5 votes
1 answer
202 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 ...
Truej's user avatar
  • 532
3 votes
1 answer
213 views

Impossible pattern in slitherlink

The puzzle here is to analyze the following Slitherlink configuration and show that it is impossible. ...
JCO's user avatar
  • 440
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 ...
quarague's user avatar
  • 1,823
9 votes
2 answers
471 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 ...
Jafe's user avatar
  • 78k
7 votes
2 answers
474 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 ...
Xavier Castillo's user avatar
2 votes
1 answer
153 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 ...
bobble's user avatar
  • 10.4k
4 votes
1 answer
282 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 ...
Sunny Lu's user avatar
  • 2,864
11 votes
1 answer
426 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 ...
Bernardo Recamán Santos's user avatar
4 votes
1 answer
372 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 "...
Sunny Lu's user avatar
  • 2,864
9 votes
1 answer
595 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 ...
Sunny Lu's user avatar
  • 2,864
16 votes
1 answer
740 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 ...
Jafe's user avatar
  • 78k
-1 votes
1 answer
155 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 ...
CrSb0001's user avatar
  • 2,241
12 votes
1 answer
494 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 ...
Jafe's user avatar
  • 78k
1 vote
1 answer
258 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?
hb20007's user avatar
  • 845
2 votes
2 answers
743 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 ...
CrSb0001's user avatar
  • 2,241
27 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 ...
Jafe's user avatar
  • 78k

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