# Questions tagged [permutations]

For questions related to permutations, which can be viewed as re-ordering a collection of objects.

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### Looking for “average” of two permutations

I am a computer programmer and I am building a search engine for a client. Right now I am puzzling myself about the order in which I should return search results. There are two obvious orderings: ...
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### Number of digits in a series of numbers

I have a list of the numbers from 1 to 1000. How can I find the number of 0's, 1's, 2's, and 9's that are used? The answers are 192, 301, 300, 300 respectively, but I'm interested in the process ...
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### Permutation/Combinations in bit Strings

I have a bit string with 10 letters, which can be {a, b, c}. How many bit strings can be made that have exactly 3 a's, or exactly 4 b's? I thought that it would be C(7,2) + C(6,2), but that's wrong (...
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### Order normalizer permutation

I would like to know how is possible to calculate the order of the normalizer of $H=\langle s\rangle$ in $S_n$ where $s$ is an assigned permutation of $S_n$. I know that finding the order of the ...
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### Unique Groups for Game Tournament

I am trying to put together a Munchkin game tournament where I am assuming I will have 16 people coming to my tournament. As part of that, I want to have as many games as possible where people are not ...
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### Proof of Permutations

With repetition allowed, You multiply the r number of times for total n objects n * n * n ... When the repetion is not allowed then you take away an object ...
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### Combination or Permutation?

I read this puzzle as below. You have 40 boxes, all placed in a row at exact intervals of 1 meter. You also have 9 balls(all same type). You wish to place all the balls in the boxes, no ...
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### Mathematical permutation drawing/visualization tool

I'm writing software and need to document an existing mathematical permutation in our code. I thought the folks here would know where I can find a drawing/visualization tool to draw a permutation ...
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### What are good ways to score an ordering?

For context, a friend hosts a pub trivia night and would like to know a good way to score ranking questions. For example, put these five movies from the 70's in order of release: Jaws, Star Wars, ...
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### Combinations and Permutations Question

I am sitting my A level exams (MEI) and I was looking through the S1 past papers and I encountered this question in the January 2010 paper: Three prizes, one for English, one for French and one for ...
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### Problem in Permutation and Combination

In how many way n identical things can be distributed among r different persons where each person may get any number of things. My book gives following ans: (n+r-1)C(r-1) but I am not able to ...
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### Permutation/Combination of x,y and z moves

First of all, I am not quite sure but I think the problem asks for a permutation/combination of 13 elements over the {x, y, z} set. Here is the problem: How many ways are there for a spaceship to ...
I didn't find any good explanation how to perform multiplication on permutation group written in cyclic notation. For example, if $$a=(1\,3\,5\,2),\quad b=(2\,5\,6),\quad c=(1\,6\,3\,4),$$ then ...
Let $\sigma$ be a permutation of $\mathbf Q.$ We call $\sigma$ bounded (the term might be somewhat misleading, but however it is used in a couple of papers) if there is a real number $M$ such that  ...