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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11 answers
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Ethan Finds the Maximum Element

This is a problem that the Hacker Cup team made for the 2018 Facebook Hacker Cup, but we ended up not using it (though Ethan struggles through a variety of other challenges). Normally code size isn't ...
Wesley May's user avatar
19 votes
9 answers
956 views

Spiral Permutation Sequence

We can roll up the natural numbers in a rectangular spiral: ...
Martin Ender's user avatar
18 votes
4 answers
625 views

Permutation group operation

There is a well-known bijection between the permutations of \$n\$ elements and the numbers \$0\$ to \$n!-1\$ such that the lexicographic ordering of the permutations and the corresponding numbers is ...
Peter Taylor's user avatar
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18 votes
2 answers
2k views

Random Golf of the Day #6: Roll a d20

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 ...
Martin Ender's user avatar
17 votes
17 answers
2k views

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 ...
Gryphon's user avatar
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16 votes
5 answers
1k views

Wolves and Chickens

There's a river and there are wolves and chickens on one side of the river. They have a raft and they all need to get to the other side. However, the raft cannot travel on its own. The raft will sink ...
0WJYxW9FMN's user avatar
  • 2,773
16 votes
3 answers
1k views

Reconstruct a Permutation

Introduction Suppose that you are handed a random permutation of n objects. The permutation is sealed in a box, so you have no idea which of the ...
Zgarb's user avatar
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16 votes
15 answers
1k views

Cheapo Enigma machine (Cops)

For robbers' post, Cheapo Enigma machine (Robbers) A cop's submission will consist of a program/function that accepts a single byte of data and return a single byte of data. Every possible input must ...
ghosts_in_the_code's user avatar
14 votes
5 answers
458 views

Generate all Brain-Flak Snippets

This question is the second of several Brain-flak Birthday challenges designed to celebrate Brain-Flak's first Birthday! You can find more information about Brain-Flak's Birthday here Challenge For ...
Riley's user avatar
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14 votes
6 answers
2k views

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 ...
user avatar
13 votes
4 answers
528 views

Possible Tetris sequences

Write code to figure out whether a run of Tetris pieces could be generated by the official Tetris algorithm. Fewest bytes wins. Official Tetris games generate the sequence of falling pieces in a ...
xnor's user avatar
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13 votes
10 answers
1k views

Permutations with Indistinguishable Items

Given a list of integers, output the number of permutations of the integers, with indistinguishable permutations counted once. If there are n integers, and each ...
qwr's user avatar
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13 votes
3 answers
678 views

Count the number of Hankelable matrices

Background A binary Hankel matrix is a matrix with constant skew-diagonals (positive sloping diagonals) containing only 0s and 1...
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11 votes
1 answer
934 views

Constructing an Orthogonal-Diagonal Greco-Latin Square

Consider a grid of NxN unique elements. Each element has a letter (from A to the Nth letter,...
Nathan Merrill's user avatar
11 votes
7 answers
785 views

Anagram Quines (Robbers' Thread)

This is a cops-and-robbers challenge the Cops' Thread can be found here Your challenge, as robbers is to take outputs from the cops' thread and find anagrams of the output that when run as a program ...
Wheat Wizard's user avatar
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9 votes
7 answers
403 views

Detecting anagrams within a Parent String

Given two strings, a parent string and a query string respectively, your task is to determine how many times the query string, or an anagram of the query string; appears in the parent string, in a ...
Eliseo D'Annunzio's user avatar
8 votes
17 answers
837 views

Cheapo Enigma machine (Robbers)

For cops' post, Cheapo Enigma machine (Cops) A robber's submission consists of a program/function that accepts the output of a cop's code and returns the input for all the outputs provided by that cop'...
ghosts_in_the_code's user avatar
8 votes
5 answers
411 views

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 ...
caird coinheringaahin g's user avatar
8 votes
9 answers
610 views

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 ...
caird coinheringaahin g's user avatar

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