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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94
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2answers
6k views

This new puzzle type needs a name

I believe I have invented a new type of puzzle... What is its name? Colour-blind-friendly version available here. Begin by solving the 16x16 sudoku; each of the digits 1-16 must appear exactly ...
81
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2answers
4k views

My God, it's full of stars!

An entry in Fortnightly Topic Challenge #32: Grid Deduction Hybrids My dear friend, unknown to us, may have relocated again. He sent me imagery and constellation maps indicating that a distant red ...
78
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1answer
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Empty sudoku puzzle

The rules are the same as for a normal sudoku puzzle. The only thing different is that instead of numbers for clues, you have greater than/less than (> <) signs between the cells. Have fun solving!...
64
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2answers
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Happy Pi-Day! Try to solve this "PiDoku"

To celebrate the Pi-Day (3/14) adequately, a challenging math puzzle must not be missing. Rules: Fill in the numbers 1-9 exactly once in every row, column, and region. On top of that, you need to ...
62
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4answers
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Gerrymandering Puzzle - Rig the Election

The following graphic is a map of the country Mathlandia: You are currently running for reelection, but the polls aren't exactly in your favor. Each square in this grid is a county. Counties with a ...
62
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2answers
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Sudoku like you've never seen it before

I've spent this week trying to create a difficult logic puzzle which is a combination of two Sudoku varaints, 'Samuari Sudokus' and 'Pseudokus', and this combo is unlike anything you can find online. ...
61
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3answers
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R.H.P.C. crossword puzzle

This is an entry into the Fortnightly Topic Challenge #36 I got a ticket to the Red Herring Puzzle Club in the middle of the street. There was just a guy giving them out, like some advertisement ...
58
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4answers
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What is the maximum number of solutions a Sudoku puzzle can have?

I've seen Sudoku puzzles that can be solved two different ways. Referring to a traditional 9x9 grid: Is it possible for a Sudoku puzzle to have more than two solutions? If so, what is the maximum ...
55
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1answer
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The Ludicrous Loop: over a thousand cells of circular logic!

Flavourtext is for flavour only. Ladies and Gentlemen, are you feeling ludicrous today? A little loopy, perhaps? Then come one, come all, for I have just the thing for you. Lampreys and Jellyfish, ...
53
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4answers
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Desert Irrigation Project

An entry in Fortnightly Topic Challenge #32: Grid Deduction Hybrids My dear friend researches and designs canal irrigation systems in a remote desert. He's been missing for two weeks. Members of ...
50
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1answer
3k views

Japanese Fusion Alphabet Soup

The Dish... ...is an intriguing blend, with a base of classic Western flavours, and a twist of the Orient at its heart. The Ingredients... ...are diverse and are combined in such an unexpected - dare ...
47
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5answers
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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 ...
46
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4answers
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Who am I??? Wait, isn't this a sudoku?

Jmw jrr qtlf tv ee M6SXr rro tr kz r tyr. Can you find out who I am? Hint 1: Hint 2:
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One 'double agent' two-step on a waltzing floor

I'm in a jam – cornered I am! – No clue 'bout where to go Here's what went down, a pretty gown Some wine, a French chateau She whispered underneath her breath "Come dance with me and ...
44
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2answers
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I am an island (ysaujdiolkiun)

An entry in Fortnightly Topic Challenge #32: Grid Deduction Hybrids I received an envelope containing two drawings and no return address. I would recognize that handwriting anywhere - my dear friend ...
43
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4answers
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Five Slitherlinks

Solve five Slitherlinks, each with a unique solution. Please say a word regarding (or show an image depicting) each solution method.
43
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2answers
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Circuit Diagram

An entry to Fortnightly Topic Challenge #35: Restricted Title 1 - based on the following xkcd. Circuit diagrams can be quite difficult to understand, so here are some documents that will hopefully ...
42
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4answers
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fill this grid with water!

In this puzzle you have to fill with water some cells of the grid. The number of filled squares in each row and column is written next to it. You can't fill a square if the squares connected to it (...
42
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2answers
2k views

Now You're Packing with Portals #1

I was staring at my window last night, and daydreaming (nightdreaming?) about filling it with shapes. Suddenly, I was struck with inspiration for a new type of puzzle! Here's a fairly easy instance: ...
40
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3answers
2k views

Animal Cross(word)ing

An entry in Fortnightly Topic Challenge #43: Variety Crossword Grids Each of the 40 clues listed below (a mix of pop culture and science/nature) yields the name of an animal. Your task is to solve ...
40
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4answers
2k views

GRID-THIRTY-SIX

Solve 36 puzzles (or more) to find the final 6 letter answer.
40
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2answers
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Magic Maze Puzzle

Inspired by the board game, Magic Maze Set-up: Cut out each 4x4 tile, and the four small tokens (orange, yellow, green and purple), from the provided image below. Place tile 1 on a flat surface with ...
40
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1answer
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Introducing: Number Slope™

Number Slope™1 is an original2 grid deduction puzzle similar to Sudoku. It is solved on an n-by-n grid, tiled with n n-ominoes. The rules are: Each number from 1 to n must occur once and only once in ...
39
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4answers
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WITLESS - A Puzzling Journey

IMPORTANT! READ ME: The only 'puzzle' parts of this are the links, titled 'Set X', 'Inscription X', or 'Constellation X'. Everything else is flavortext, apart from this readme section, although the ...
39
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1answer
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This new puzzle type needs a name {EXTREME EDITION}

A companion puzzle to the 'This new puzzle type needs a name' series, and inspired in part by @JeremyDover's answer to a recent question. Usually, puzzles in this series comprise a mash-up of two ...
38
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6answers
2k views

Sudoku embedded in a Kakuro

In addition to standard Kakuro rules, the grey shaded cells must form a valid Sudoku solution. One sum in this puzzle has been corrected from 28 to 23. Fortunately, it was in a location that nobody ...
38
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1answer
1k views

Didn't you ask me for a crossword?

An entry in Fortnightly Topic Challenge #forty-seven: "Wacky Sudokus" Here's that crossword you asked for... Sorry, what's that - you didn't ask me for a crossword?? TASK: Solve the puzzle ...
38
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2answers
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Q: What kind of logic puzzle would you like? A: Yes

A recent post and Stiv's answer provided inspiration for a new puzzle. I posted a study for this puzzle earlier; this is the bigger effort envisioned. I hope you enjoy! This puzzle consists of four ...
36
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4answers
2k views

Sjudoku - in a world where 9 is replaced by 7

Sjudoku (sju = seven in Swedish). Rules similar to Sudoku applies: In each disk, the numbers 1,2,...7 should appear exactly once. No line may contain duplicate digits (note that there are lines in 3 ...
35
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3answers
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The Determinant Sudoku

The determinants of $2\times 2$ matrices are calculated this way: $$\det\begin{bmatrix}a & b \\c & d \end{bmatrix}=ad-bc$$ And here's the sudoku-determinant puzzle: What's the solution for ...
35
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4answers
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Self-contained math crossword with if-then-else clues

An entry in Fortnightly Topic Challenge #43: Variety Crossword Grids Since I'm not good with with words and crosswords, here is a math crosswords: to know all the operands for the calculations you ...
33
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2answers
3k views

I've been everywhere, man

I am a knight facing a plight My dearest one of all Lives in a tower and won’t come out Unless her name I call I went to pick her up today And though my mind was set To do so, as I ...
33
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1answer
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MASTERING Sudoku

Fill the grid with letters M, A, S, T, E, R, I, N and G. Standard Sudoku rules apply. Additionally, the words on the right-hand side must appear in the given orientation (across/down). Each word ...
32
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2answers
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Question 16 Ripple Effect

This is a Ripple Effect puzzle. The rules of this puzzle are: Fill in each region with numbers from 1 to n, where n is the region size. For instance, the top left region must have the numbers 1 to 5 ...
32
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6answers
2k views

A Six-Faced Puzzle

Here is a grid-deduction puzzle, whose mechanics I have seen under several names such as 'Castle Wall', which is the one I'll use here. The goal of Castle Wall is to draw a loop enclosing all the ...
30
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2answers
2k views

Parallelisation

An entry in Fortnightly Topic Challenge #32: Grid Deduction Hybrids Puzzlers, I am presenting a set of six duo-grids! Of course, I need to tell you how they work - you are given a grid. Looking at it,...
30
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3answers
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Messages hidden in the "visit every square once" puzzle

I proposed my girlfriend yesterday, asking her to be my wife. but she did not answer me. Besides she gave me this 6 puzzles, below. She said I will know her answer after solving the puzzles. Inside ...
30
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1answer
652 views

Pikurossword, or: Three-in-One

This is an entry into the Fortnightly Topic Challenge #36. [edit: i hope this wasn't too bad for my first puzzle here! let me know how i did :)] The answer to this puzzle should answer the question: ...
29
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7answers
5k views

Almost impossible Sudoku like puzzle

I was set a puzzle in my math class. I tried to do it using an equation but it didn't work it looked like a trial and error puzzle so I took it into school and the math teachers couldn't solve it. Is ...
29
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4answers
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Curiouser and Curiouser

CHAPTER ONE Alice was beginning to get very tired of sitting by her sister on the bank, and of having nothing to do: when she was overcome with the strangest sense of deja vu, and saw a 7x3 grid of ...
29
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3answers
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Oh no, it's another safe!

An entry in Fortnightly Topic Challenge #32: Grid Deduction Hybrids Oh, did I feel proud after solving the last safe... until I was immediately dimension-doored (or something) into this room! Damn ...
29
votes
1answer
921 views

A flag-packing problem

An entry in Fortnightly Topic Challenge #45: Flags You are provided with a 9x9 grid of squares and 21 minimalistic flags (pictured below, all shown to scale). TASK: Assign a colour (Black, Blue, ...
28
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11answers
4k views

Is there a puzzle that is only solvable by assuming there is a unique solution?

Is it possible to construct a puzzle that is: Solvable if you assume there is a single unique solution Not solvable if you do not make this assumption My intuition says that the answer is "No&...
28
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5answers
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Making Things Difficult

An entry in Fortnightly Topic Challenge #35: Restricted Title 1. Factoring the Time Think fast! If you're looking for meaning, these clocks have some for you. Keyboards are Disgusting Gunky ...
28
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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 ...
28
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3answers
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Coloring a 4 by 4 grid

I made this simple puzzle a couple of years ago. There are three colors which appear in every row and every column. Moreover, every color appears 5 or 6 times in total. Find the color of the square ...
28
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1answer
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This new puzzle type needs a name {3}

I believe I have invented** a new type of puzzle... What is its name? ** Well, 'adapted' an existing one, really... Colour-blind-friendly version available here. Those without colour-blindness ...
28
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2answers
761 views

Tribute to Clifford Possum Tjapaltjarri

The background text that follows is in this case not part of the puzzle, nor fictitious. The puzzle, which is self-contained, consists entirely of the image below; I have composed it as a genuine (...
28
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1answer
936 views

Every Fourth Wormhole

An entry in Fortnightly Topic Challenge #33: Surface Geometry Mazes
28
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1answer
967 views

You go wherever you go today

A conclusion to my entries in the Fortnightly Topic Challenge #32: Grid Deduction Hybrids. This metapuzzle incorporates the three previous puzzles in this series: Desert Irrigation Project I am an ...

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