# Questions tagged [permutations]

A permutation is a particular ordering of some list of objects. Problems tagged with permutation usually involve finding or generating permutations, including anagrams of text.

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### Doce logf a string swapper [closed]

Challenge Take an input string $s$, and split it into words $w_1, w_2, ..., w_n$. If the amount of words is odd, then return $s$. Otherwise, for each word: Take the second last letter, and swap ...
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### 9erilous 9ermutations

Note: This is an attempt at recycling guest271314's permutation question(s) There's an interesting pattern that forms when you find the differences between lexographically sorted permutations of base ...
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### Amidakuji (阿弥陀籤) simplification

If you have ever had any exposure to Japanese or East Asian culture you will have surely encountered the Amidakuji game: As Wikipedia explains, it is a type of lottery drawn on paper and used to ...
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### Encode - Shuffle - Decode

Challenge Your task is to encode an integer as a string of ASCII characters, then successfully decode it after said string has been randomly shuffled. You will write two programs/functions, which ...
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### What is the simplest reversible circuit that computes conjugacy of transpositions?

Reversible computation refers to computation in which little or no information is deleted. Reversible computation a major component of quantum computation, and reversible computation is potentially ...
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### Permutation Encoding

Write a program which can encode text to avoid reusing characters, and convert back. Both normal and encoded forms are restricted to a particular character set: the space character ...
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### Code golf the best permutation

Challenge Given an integer n ≥ 4, output a permutation of the integers [0, n-1] with the property that no two consecutive integers are next to each other. The value of a permutation ...
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### Block Rearrangement

So your task is to take a 3x3 block where -'s mean blank spaces, and *'s mean filled spaces, for example: ...
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### Levi-Civita symbol

The three-dimensional Levi-Civita symbol is a function f taking triples of numbers (i,j,k) each in ...
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### Codegolf the Hafnian

The challenge is to write codegolf for the Hafnian of a matrix. The Hafnian of an $2n \times 2n$ symmetric matrix $A$ is defined as: \operatorname{haf}(A) = \frac 1 {n!2^n} \sum_{\sigma \in S_{...
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### Conjugate permutations

A permutation of size n is a reordering of the first n positive integers. (meaning each integer appears once and exactly once). Permutations can be treated like functions that change the order of a ...
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### Stitch Together a Palindrome from Palindromic Substrings

Given a string l, find all palindromic substrings p of l (including duplicates and single ...
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### Deranged Rearrangements

Your task is to write a computer program such that when it is cut up into lines (split on the newline character) every arrangement of the lines will output a different number between 1 and n! (where n ...
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### Flattened Spiral Permutation Index

Context Consider square matrices with n columns and rows containing the first n^2 (i.e. n ...
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### How many draws are there in Quarto?

Introduction This challenge is similar to Project Euler problems. I came up with it because I was playing a deceivingly simple board game and couldn't come up with an efficient solution to answer a ...
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### Find The Rank Of A Word

Definition The rank of a word is defined as the position of the word when all the possible permutations (or arrangements) of its letters are arranged alphabetically, like in a dictionary, no matter if ...
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### Generate combinations that add up to a target value

Challenge Suppose you have a list of numbers, and a target value. Find the set of all combinations of your numbers which add up to the target value, returning them as list indices. Input and Output ...
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### ​L​o​o​p​ ​I​t​

Note: The title of this question should be "Loop It", but because title needs to be at least 15 characters, there are some invisible spaces. This note is such that the challenge can be ...
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### A Dance of Many Dimensions

Challenge Given a n-dimensional array of integers and a permutation of the first n natural numbers, permute the array dimensions ...
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### Riffle shuffle a string - Robbers

Cops post A riffle shuffle is a way of shuffling cards where the deck is split into 2 roughly equal sections and the sections are riffled into each other in small groups. This is how to riffle ...
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### Riffle shuffle a string - Cops

Robbers post A riffle shuffle is a way of shuffling cards where the deck is split into 2 roughly equal sections and the sections are riffled into each other in small groups. This is how to riffle ...
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### String Permutations - case and order [duplicate]

Challenge For any string that is composed of alphabetical characters of any case, make a function that returns a list of all of it's variations, order and case-wise empty strings returns empty list. ...
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### N-bit Variation on Subset-Sum

For another challenge I am writing, I need to verify that test cases are solveable with bounded integers. Specifically, I need to verify the following, for a non-empty array of integers ...
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### Days and months make years

Today's date is quite an interesting one. Let's take a look at why. The date 07/12/2017 (in DD/MM/YYYY date format) can be split ...
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### Build this pyramid

Your pyramid The pyramid I want you to build is made entirely of cubes. It has 24 layers, and the Nth layer from the top contains N2 cubes arranged in an N by N square. The pyramid looks like this: ...
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### Output an Anagram! No Not That One!

Given a list of unique strings that are anagrams of each other, output an anagram of those words that is different from each word in the list. The strings will be alphanumeric, and there is guaranteed ...
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### Output all distinct permutations of a vector

Challenge: Output all distinct permutations of a, potentially long, list of positive integers. You may assume that the vector has less than 1,000 numbers when testing, but the process should in ...
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### Those annoying grasshoppers [closed]

The problem #6 of IMO 2009 reads: Let a 1, a 2, a 3, ..., a n, be distinct positive integers and let T be a set of n-1positive integers not containing a 1+a 2+a 3+...+a n, A grasshopper is to ...
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### Numbers with similar powers

Given an integer p > 1, find the smallest integer q > p such that the list of exponents in the prime factorization of q is the same of that of p, no matter the order or the value of the prime ...
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### The Original Number (II)

This challenge is essentially identical to this one with just one difference: it is now allowed to shuffle letters anywhere in the string. Scenario John has an important number, and he doesn't want ...
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### Reliably Broken Sort

Given a list of positive integers that contains at least 3 distinct entries, output a permutation of that list that isn't sorted in ascending or descending order. Examples ...
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### Bubble the brackets!

There are a few questions on this site about balancing brackets, and checking whether brackets are balanced. I propose it's now time to use those balanced brackets for something! In mathematics and ...
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### Construct a Permuter

For this challenge you are going to make a function (your function may be a complete program) that takes a list as input and returns a permutation of that list. Your function must obey the following ...
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### Color me a Pole

Lets say your job is to paint poles, and a client asks you to paint a pole with 4 red sections and 3 yellow sections. You can do that pretty easily as follows: ...
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### The Original Number

Guidelines Scenario John has an important number, and he doesn't want others to see it. He decided to encrypt the number, using the following steps: His number is always a non-decreasing sequence (ie. ...
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### Counting from 1 to n without any consecutive numbers

Goal You are given an integer n (n > 1). You must output how many permutations of the integers ...
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### Smallest unused number sharing a factor

This is a pretty run of the mill question. I will define a sequence and you golf some code to output a entry given a index. The first item in the sequence is 2. The nth item in the sequence is the ...
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### Solve an Anagram

See also: Granma loves Ana You will be given a string of lowercase ASCII letters. Using this dictionary file (UPDATED), your task is to solve the anagram. To solve an anagram, you must output all ...
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### Find all the Anagrams, and the Subanagrams too!

This question is heavily based off this question, but should pose a number of additional difficulties. Your Task You must write a program or function that, when receiving a string, prints out all ...
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### Find all the Anagrams!

Despite having 17 questions tagged anagrams, we still don't have this question, so here it is. Your Task You must write a program or function that, when receiving a string, prints out all possible ...
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### Is that string garbled? [duplicate]

Mayube recently posted Garble that string. However, humans aren't too good at checking whether a string is actually garbled or not. (Actually, that's an understatement, we are really bad at it.) So, ...
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### Garble that string!

Given a string as input, output one or more variants of the string such that: No character is in it's original position No character is adjacent to a character that it was originally adjacent to You ...
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### Golf an Anagram Quine

In this question I asked you to guess an anagram quine based on its output. However it looks like we don't have a question asking to golf an anagram quine yet. So your task will be to make the ...
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### THE Magic Hexagon

There are many magic squares, but there is just one non-trivial magic hexagon, as Dr. James Grime explained, which is the following: ...
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### Find a binary needle in a decimal haystack

The challenge You're given: a non-empty, unsorted list h of positive integers (the haystack) a positive integer n (the needle) Your task is to return the list of all unique decimal concatenations ...
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### Golf you an anagram for great good!

The Task In this challenge, your task is to write some code which outputs one of its anagrams chosen randomly with uniform distribution but it should never output itself. Elaboration Given no input, ...
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### It's Anagram Quine, not just Quine!

The Task In this challenge, your task is to write a program, which takes in no input, with as many anagrams that are quine of themselves as possible. Your score will be the number of anagrams of your ...
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### Random Golf of the Day #8: Shuffle an infinite list

About the Series First off, you may treat this like any other code golf challenge, and answer it without worrying about the series at all. However, there is a leaderboard across all challenges. You ...
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### Scramble words while preserving their outlines

This is much more advanced than How to randomize letters in a word and Cambridge Transposition because of the rule about which letters may be swapped with which. A simple regex will not suffice here. ...
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