Combinatorics is a branch of mathematics concerning the study of finite or countable discrete structures.

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Generate all permutations in Clojure

Given a set, generate all permutations: (permutations #{1 4 5}) => ((5 4 1) (4 5 1) (5 1 4) (1 5 4) (4 1 5) (1 4 5)) Here's what I cobbled together: ...
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Comparing algorithms for computing binomial coefficients in Java

I have these 3 different algorithms for computing binomial coefficients (I also had the 4th recursive one, yet I discarded it since it is super slow). The first uses the factorial formula, the second ...
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63 views

Generating vertices of the rectified hypercube

The following piece of code generates the vertices of the rectified hypercube in arbitrary dimensions. The 3D case of the rectified hypercube is a cuboctahedron with 12 vertices (±1,±1,0), (±1,0,±1), (...
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86 views

Iterative solution for generating all permutations of a string

I know the runtime for generating all permutations is supposed to be \$O(n!)\$. I'm not sure if the code I wrote for it runs in \$O(n!)\$ though. I'm having trouble analyzing its runtime. The ...
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Permutations part two

This is a follow up from this question. The goal is to make some function that can return the number of possible permutations with repetitions. As Gareth pointed out there is a nice formula for this ...
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Counting permutations without repetitions for a number or a string

Can I make the following code faster with minor modifications? It times out on CodeWars website. ...
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127 views

Computation of product of permutations

Given a graph \$G = (V,E)\$ with a unique labeling of each vertex, let the transposition \$(i,j)\$ (where \$i,j\$ are the labels on adjacent vertices) represent selecting an edge and swapping the ...
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52 views

Find all distinct combinations of letters in a string

I've been preparing for interviews and picking up modern C++. A recent prep question I did was to find all combinations (or distinct subsets) of letters from a string. E.g. ...
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31 views

Form every unique combination of the items of a list of lists

I've tried looking some stuff up. I thought it was transposition first, but looking at this, that's not exactly it. I hacked this code together in about 3 hours, stopping frequently due to ...
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Give the variable length permutations (combinations) of a set of strings

This code is a proof-of-concept which I intend to convert into a static utility / helper class. I'm looking at this review from a structure or performance viewpoint. Small detail such as whether it ...
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40 views

Summative Pattern

While playing around with J (link), I found that you can create a sequence of shape N0 N1 ... NK with i. taking a list as its ...
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79 views

3D Bin Packing using Java

This is a follow up question to 3D bin packing in Java ...
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all combinations of all sizes less than N

I want to generate all possible combinations (without duplicates) of all sizes less or equal than \$N\$, so for example if \$N=3\$ I want to generate the following \$\{1\},\{2\},\{3\}, \{1,2\},\{1,3\},...
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Permutations with repetitions algorithm in R

Given a string of length n, print all permutation of the given string. The code bellow generates all permutations (with repetitions) for the given string and stores them in object ...
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58 views

3D bin packing in Java

I made some changes to the first code here I wrote and I want to know which one is more correct logically (before the changes or after the changes). It's really hard to manually test these kind of ...
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1answer
108 views

3D bin packing algorithm using Java?

I wrote a 3D bin packing algorithm but I am still not sure if it is correct or not. I did not follow any code or pseudo-code that's why I would like to know if it is an efficient algorithm for the 3D ...
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2answers
119 views

Finding all contiguous sublists such that each member appears an even number of times

The program needs to find all contiguous sublists of numbers where the number of occurrences of every member in the contiguous sublist is divisible by 2. The first line of input is N (the number of ...
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2answers
247 views

Java 8 Stream to produce all permutations of an array using recursion

I want to write a class that returns a Stream of permutations of an int[]. ...
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5answers
255 views

Pizza Hut math problem #1 in Haskell

I'm currently attempting to learn Haskell after a fair history of imperative programming. When I saw the Pizza Hut Pi Day math problems, I thought the first one would be a good candidate for my ...
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Finding Kth Permutation Sequence

I have written a program to display the kth permutation sequence of a string made up of letters 'O' and 'Z' . I tried optimizing it but my code have not passed test cases due to timeout issues.Looking ...
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Characters set permutations with repetitions

The code bellow generates all the permutation(with repetitions) for given character set. Is there any better(simpler, more performant) way to do that? ...
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1answer
114 views

Finding ways to achieve a target sum using recursion

I need your review and suggestions how to make this code better. I'm just learning recursion and sure that this solution is not ideal. Question: Write a function that given an input array of ...
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103 views

Korean word segmentation using frequency heuristic

This a continuation of a previous question. I want to thank Joe Wallis for his help with increasing the readability of my code. Although the changes made by Joe Wallis did increase the speed of the ...
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1answer
137 views

Round Robin Tournament

RoundRobin is an implementation of the Round-robin style tournament: ...
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2answers
71 views

Making the same amount from different combinations of coins (top-down approach)

I was reading a typical interview question found here. Given an amount and a list of denominations, count the number of possible ...
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1answer
66 views

Improving Speeds of Tokenisation of large word list for distinct combinations

I'm having trouble with a current algorithm I'm writing that takes a corpa, a list of characters in sets (1 one or larger) with a frequency number attached to it. Against another list of character ...
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57 views

All possible ways of merging two lists while keeping their order

I am writing a function gives all possible ways of merging two ordered lists such that in the merged list, the elements are still ordered according to the elements in their respective starting list. ...
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2answers
111 views

An iterator returning all possible partitions of a list in Java

Given a list of \$n\$ objects and an integer \$k \in \{ 1, 2, \dots, n \}\$, this iterator generates all possible ways of partitioning the elements in the list into exactly \$k\$ disjoint, non-empty ...
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152 views

An iterator returning all possible permutations of a list in Java

I have this class that iterates over all permutations of an input list: PermutationIterable.java: ...
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Generate Subsets Of K Elements From A Set Of Strings

This is the task: Write a recursive program, which prints all subsets of a given set of N words. Example input: words = {'test', 'rock', 'fun'} ...
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Combination generator in Java - 2nd iteration

I have refactored the previous combination generator, and now it is an iterator returning combinations as lists. It hides larger constant factors as the previous version, yet it is really easy to use: ...
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multirange iterator

I'm doing some boring math with lot of sums over lot of variables. So, instead of nesting for loops I have decided to use something like this: ...
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800 views

Generate a dictionary of passwords

I have a Python script that generates a dictionary of all possible 3 digit password combinations. It essentially works by just nesting for loops. This is fine, but ...
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564 views

Solution to King Kohima problem in Python

King Kohima problem: King Kohima has reserved a new exclusive street for his executive class employees where they can build their homes. He has assigned you to plan that street. You have to ...
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1answer
145 views

Combination generator in Java

(See the next iteration.) Given a positive \$N\$, the following class generates all possible non-empty sets \$A \in \mathcal{P}(\{0, 1, \dots, N - 1\})\$ in lexicographic order. Also, it provides a ...
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1answer
94 views

Scala implementation of @rolfl's integer-partitioning algorithm

While reviewing @Martijn's Distinct sums of integers (finding all combinations of positive integers that sum to a given number), I proposed the following solution: ...
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C permutation generator

I am making a permutation generator in c. Any ideas how I can make it faster? ...
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91 views

Searching a string for any permutation of words

Given a string and an array of words, return all indexes in string for which a concatenation of all words in the array, in any order (so ["eensie", "weensy", "spider"] has six orderings) can be ...
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137 views

Recursive program for generating and printing all permutations of the numbers 1, 2, …, n for given integer number n

I've just written code for generating all permutations of the numbers from 1 to n in Java. It seems to work, but I think it's a bit more complex than it needs to be. ...
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111 views

Permutation function in C#

One thing lead to another and eventually I wanted to know the "proper" way of writing the permutation generating function in C#. Below is my code for generating permutations. This will go into an ...
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572 views

isPermutation method

I wrote an isPermute method. Can I get some tips and advice on better coding style? ...
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Printing all possible sums of two n-sided dice rolls

For my CS class, we were tasked with writing a program that calculates all the possible results from rolling two n-sided dice. For example, the input of 4 would ...
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Finding tuples of numbers subject to constraints

I just watched the video from "Think Like a Programmer, Episode 2: Puzzles & Problems". The problem is: Assign number 1-7 to three departments in a city: Fire, Police, Sanitation. ...
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158 views

Finding permutations of a word

This was a basic anagram problem. Take an input word, find all its permutations, then check a dictionary file to see what if any of those are real words. Dictionary file My input data: ...
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148 views

Counting paths in an n-dimensional grid that stay within the boundaries

Problem Statement You are situated in an N dimensional grid at position (x1, x2, …, xN). The dimensions of the grid are (D1, D2, …, DN). In one step, you can walk one step ahead or behind in ...
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280 views

Programming Challenge from Kattis: Apparatus

I am trying to solve apparatus problem, paraphrased below. There is an apparatus with n on/off switches with a one-to-one correspondence to n lights (but with an unknown permutation). We have ...
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129 views

Permuting a typelist

Given a typelist, return a typelist of all the permutations of it. For example: ...
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83 views

`r` permutations of `n`

I have written this snippet to find r-permutations of n, i.e. if I have an array of n=3 {0,1,2}, then r=2 permutations will be {{0, 1}, {0, 2}, {1, 0}, {1, 2}, {2, 0}, {2, 1}}. Can somebody review it ...