All Questions
Tagged with logical-deduction combinatorics
92
questions
5
votes
2
answers
321
views
Number of 3x3 One Up puzzles
Rodolfo Kurchan created a wonderful new grid puzzle called One Up that you can play on his website. There is one main rule:
Each horizontal and vertical sequence of N cells between walls, must contain ...
- 36.3k
19
votes
3
answers
2k
views
Playing Mastermind against an angel and the devil
This puzzle is based on a card game. There are 7 suspects and 3 of them committed a crime. The game contains 35 cards that contain the 35 possible choices of 3 out of the 7 suspects. One card is drawn ...
- 1,863
5
votes
1
answer
437
views
Counting Tic-Tac-Toe draws on larger grids
Alice and Bob play a game of Tic-Tac-Toe on a grid of size $N \times M$. The rules of this game are the same as the original Tic-Tac-Toe:
Alice plays first (white); Bob plays second (black).
On each ...
- 15.9k
2
votes
1
answer
254
views
Good and bad numbers of remaining mines
You've been tasked with finishing solving this Minesweeper board:
"How many mines remain?", you ask. "I'm just choosing that now, actually. Tell you what: I was going to consider every ...
8
votes
2
answers
582
views
How many Nonconsecutive Sudoku solutions are there?
Consecutive Sudoku is a variant with the additional rule that orthogonally adjacent numbers are consecutive if and only if there is a dot/bar on the line between them. A Nonconsecutive Sudoku is one ...
- 10.4k
33
votes
8
answers
3k
views
Two out of a dozen cartons have Easter eggs. Two people try to find one Easter egg carton, each using a different strategy. Who is expected to win?
I have found a counter intuitive puzzle. I have read the answer given at the source and understand it completely. But, what I am unable to understand is why my intuition turned out to be wrong. ...
- 3,193
16
votes
2
answers
800
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 ...
- 28.7k
21
votes
2
answers
1k
views
Beans under the chessboard
Under every grid cell of a chessboard, I put either one bean or nothing.
Now if you choose a (grid) rectangular area on the chessboard, then I will tell you the parity of the number of beans under ...
- 7,405
7
votes
1
answer
324
views
A 3x3 grid with common factors
A $3 \times 3$ grid $G$ is filled with every number from the set $\{2,3,5,6,7,11,14,15,30\}$. Now a new $3 \times 3$ grid $H$ is formed, such that $H_{ij}$ is the number of neighbors of $G_{ij}$ that ...
- 36.3k
10
votes
4
answers
1k
views
Deriving a 3x3 grid from another one
A $3 \times 3$ grid $G$ is filled with every number from $1$ to $9$. Now a new $3 \times 3$ grid $H$ is formed, such that $H_{ij}$ is the number of neighbors of $G_{ij}$ that are greater than $G_{ij}$....
- 36.3k
9
votes
1
answer
594
views
Plants vs Zombies!
Several plants and zombies (no more than 20 creatures in total) came to the party “Plants VS Zombies”, and it turned out that all the creatures are of different heights. When a plant speaks to a lower ...
- 315
3
votes
1
answer
284
views
Swapping eggs puzzle
You can try this with pencil and paper, or make it a physical puzzle you can try out with your kids if you have one of those large 3x6 egg cartons laying around.
Imagine you have 3 rows of 6 spots. ...
- 33
7
votes
1
answer
218
views
My two button microwave
Long ago, I encountered a microwave with a display in the "HH:MM:SS" format. But instead of a number pad, you entered the desired time through two buttons:
An "up" button, which ...
3
votes
1
answer
280
views
Variation of 100 Prisoners' names in boxes
100 Prisoners' Names in Boxes
The following puzzle is a variation of the above puzzle.
Names in Boxes
The names of 4 prisoners are placed in 4 wooden boxes , one name to a box, and the boxes are ...
- 3,193
2
votes
2
answers
188
views
3 switches and 4 lights
The are three switches (1, 2 and 3) and four lights (A, B, C and D). Each switch turns on exactly two lights and no two switches turn on identical lights. You know that
Lights A, B and C are on when ...
- 36.3k