# All Questions

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### character decoding problem at an interview [closed]

If "PSAKLJIUASP" is "PJIUAZAKLKP", then what is the word for "LIOQWERRPOIL"? I noticed that the first 3 characters are reverse of the last 3 characters in both words in question. A is mapped to I ...
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### Optimal play for 2 by 2 dots and boxes

Consider the classic pencil and paper game Dots and Boxes . You can assume the 2 by 2 version (that is with 9 dots). Starting with an empty grid of dots, players take turns, adding a single ...
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### The smallest crossword

I heard Martin Gardner in one of his books presented a crossword, which looks like 3x3 square. Could you help me to find it? Also, have been there a smaller crossword puzzle created?
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### A haunted vending machine that you can't see inside

This question asks about a strange vending machine in which coins can fall out as well as being deposited in, and all the coins it asks for must be deposited before the machine will accept them. That ...
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599 views

### Identify unique Verbal Arithmetic Puzzles

I am attempting to create original Verbal Arithmetic puzzles such as the famous one from this question Alphametic (Verbal Arithmetic) general strategy : SEND+MORE=MONEY For these problems each ...
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### How to create a pure mathematical-logical based puzzle equivalent to resistance based physical puzzle?

I am thinking how to reformulate a physical puzzle in a way that it becomes purely logic based (doesn't uses physical lows and can be solved by a person, who knows nothing about physics). The puzzle: ...
794 views

### Is there a retrograde analysis puzzle like “Point on the incorrectly drawn chess piece”?

Does anybody know a nice chess puzzle, where the question states: Exactly one piece is drawn incorrectly on this diagram; another piece must be drawn on its position. Find the incorrectly drawn ...
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### Is there a more efficient way to rotate the centre pieces on the Octo-Star?

I'm looking for a more efficient algorithm to rotate the center column of the Octo-Star puzzle 45 degrees. The situation below occurs when four properly-oriented edges are next to each other, ...
58k views

### Which way is the bus going?

If I'm not mistaken, this is a children's puzzle, but it got me thinking for a while. The bus is driving on the autobahn. Relative to you, which way is the bus going? Left or Right?
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### How can I solve the Gear Cube Extreme?

The Gear Cube Extreme is another Mechanical Puzzle. I ordered it not so long ago and a friend of mine "accidentally" scrambled it. Now I want to solve it again but I have no idea how or even where to ...
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### Is there any way to 'trap' my opponent on Connect Four?

I am trying to find out if there are any 'optimal' moves in the game, so as to trap my enemy to put his pawns in the place where I need them
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### 5x5x5 Rubik's Cube Smiley

I did some turning on my 5x5x5 Rubik's Cube and I now have the cube like on the image below. 4 times a smiley -_- and 2 times a solved plane. But I have no idea how ...
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### Is there a rating system for crossword puzzles?

On searching the internet for difficult crossword puzzles I find that the New York Times is often mentioned. But is there a rating system? If so how does it work?
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### Why must a sudoku have a unique solution [closed]

Why must a sudoku have a unique solution. In my books I don't guarantee it. But I am sure there are not many which don't. I doubt if one in a thousand dont have. And even if they don't its only a ...
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### What is the position in chess with the longest string of moves before mate?

In chess puzzles, the objective of the puzzle is usually to checkmate the opponent using some form of novel strategy or tactic. For example, the following puzzle (from here): has white to play and ...
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### Fastest way to collect an arbitrary army

I am looking for solution of this puzzle: There is a kingdom with a square shape with sides of length 1. The castle is located at the center of the square. At the castle the king lives under the ...
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### Clever ways to solve Mastermind?

Is there any specific way to solve Mastermind? Apart from the first step that is pure chance, is there any way to continue based on the colors that you think are correct?
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### How does one make a program to provide all the 'possible' numbers in an empty cell

To be able to solve a sudoku one usually has to first work out all the 'possible' numbers in an empty cell. How can one make a program to do this? In this case 'possible numbers' are ones which have ...
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### How many distinct unsolvable Rubik's cubes exist?

I wanted to answer this question: Why can't I have only one edge piece flipped on a 3X3 Rubik's cube? by saying that it is homomorphic to the illegal state in this question: Why is a ...
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### Odds of duplicate birthdays

I found the following problem in an number of places online: John once bet a fellow gambler that two of the first thirty persons they met and spoke to would prove to have the same birthday. Strong ...
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### Why can't I have only one edge piece flipped on a 3X3 Rubik's cube? [duplicate]

I was using the beginner method to deliberately solve a 3X3 cube with one edge piece flipped. But, by the time I got to the top I discovered that I couldn't solve it with only one edge flipped. I had ...
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### The Magic Stick

Here's a relatively easy puzzle that's actually entirely my own creation. An old guru in an Asian monastery is showing his beloved student his gallery of items that he has either collected or kept ...