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

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Optimizing unique partitions of integers

I am working on a project involving the unique partitioning of integers. I.e. I am looking to have all of the partitions of n = x1 + x2 + x3 + ... + xk, where xi = xj implies i = j. For example, if I ...
7
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1answer
68 views

Compute stats on two class vectors

Below is a full working code example of code which is used to compute stats on two class vectors (partitions). There are two functions: pairwise_indication and ...
9
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2answers
87 views

Printing permutations of a given string

I want some feedback on the program I developed in C for printing the permutations of a given string. ...
0
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1answer
65 views

Finding the number of permutations of an integer array with equaling difference (not in order)

The array size is <= 16. The difference is defined as: diff[i] = array[i+1] - array[i]; I need to find the number of permutations of the original array, which ...
3
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0answers
187 views

Nonogram puzzle solution space

I've written some code to brute-force enumerate the solution space of nonogram puzzles up to a certain size. It does a good job up to the first ~4 billion puzzles, but I run out of disk space to store ...
7
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2answers
120 views

Generate permutations with symbols

Goal: Create a combination of emails based from inputted first name, last name, middle name, and a domain. Add in common separators. Then I'll check which one is correct with the rapportive API. This ...
1
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0answers
48 views

Find the combinations, given three datacenters with x number of machines [closed]

I am working on a project in which I have three datacenter (as of now) and each datacenter will have some machines. So I am storing the input in a ...
5
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1answer
106 views

Project Euler #15 in haskell

I've solved Project Euler #15 in Haskell, but I feel like there might be a better way to express my solution that I'm not seeing. I start out defining my types: ...
3
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2answers
198 views

Permutation of a string eliminating duplicates

This code lists the permutations of the string, and eliminates duplicates if any. I'm looking for code review, best practices, optimizations etc. Also verifying complexity: O(n! * n) as time ...
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2answers
508 views

Calculate all possible combinations of given characters

I was asked in my textbook Lectures on Discrete Mathematics for Computer Science to construct a program that would take an alphabet ({a,b,c} or any combination of ...
5
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2answers
134 views

Print routes on the stairway when only 1 or 2 steps are possible

Given a staircase with N steps, you can go up with 1 or 2 steps each time. Output all possible ways you go from bottom to top. I'm looking for code review, best practices, optimizations etc. ...
3
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1answer
150 views

Find all permutations of a string in C++

I need a review of the following code for finding all permutations of a string in C++: ...
10
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3answers
1k views

Brute Force Algorithm in C

This is a simple brute force algorithm I have in C. All the program does it print out every possible combination of the given alphabet for the given length. I ...
0
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1answer
205 views

Fastest way for working with itertools.combinations

I need to speed up the function below: ...
2
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1answer
36 views

Produce product of lists

I want to combine elements in different lists. For example, here are 3 lists. list_a : [ 1,2,3 ] list_b : [ 4,5,6 ] list_c : [ 7,8 ] Selecting elements from ...
3
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2answers
100 views

Determine if a word can be constructed from list of subsets - follow-up

I have reworked my code as suggested from my previous question: Determine if a word can be constructed from list of subsets. Please instruct me on the complexity along with a review feedback, as ...
2
votes
2answers
121 views

Determine if a word can be constructed from list of subsets [closed]

The question is explained well by examples in the comments below. Also I request verifying complexity: O( n * n!), where n is the number of words in the subsets. Review my code for optimizations, ...
4
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2answers
125 views

Integer Partition using an iterator

I tried implementing Integer Partition (enumerating all possible sets of whole numbers whose sum is a given integer). Looking at @rolfl's answer, I reasoned that with a stack data structure, we ...
3
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3answers
132 views

Permutation algorithm: What is so bad about this code?

I was asked to write a permutation algorithm to find the permutations of {a,b,c}. Since this is a famous question to which an answer is readily available online, I wanted to do it a little ...
6
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2answers
101 views

Integer Partition

The aim is to enumerate all possible sets of whole numbers whose sum is a given integer. ...
3
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1answer
88 views

Better way to create samples

I've done this piece of code for creating all possible samples without repetitions, but I think that it is a so heavy algorithm because every time I call this recursive function I create a new vector ...
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6answers
1k views

How can I make this mess of Java for-loops faster?

I'm trying to find all the 3, 4, 5, and 6 letter words given 6 letters. I am finding them by comparing every combination of the 6 letters to an ArrayList of words ...
6
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1answer
3k views

Find all subsets of an int array whose sums equal a given target

I am trying to implement a function below: Given a target sum, populate all subsets, whose sum is equal to the target sum, from an int array. For example: ...
1
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1answer
61 views

Increase efficiency of card-ordering program

As mentioned in @rolfl comment. What this program does is that it "resequences the cards using a fixed system and count the number of times the resequencing happens before the output is the same as ...
2
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0answers
41 views

TLE for SPOJ Upper Right King

I am solving this problem on SPOJ Upper Right King (Hard). I've written a solution in Python with a time complexity of O(n(logm)2). But it's showing TLE. Can anyone help me out with this? For more ...
2
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1answer
358 views

Ugly numbers problem

Taken from one of codeeval.com challenges (https://www.codeeval.com/open_challenges/42/): Challenge Description: Credits: This challenge has appeared in a google competition before. ...
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2answers
165 views

Improving run-time and max-digits of digit summing code

As a challenge I decided to do the following problem: How many different numbers with n digits are there whose digits add up to k As this is an embarassingly parallel problem I decided to use a ...
3
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1answer
112 views

How to improve this permutations program?

I wrote a small program which shows all possible permutations of choosing m integers from the set {1, 2, ..., n}, as follows: ...
2
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1answer
161 views

Python infinite product generator

I have the code below to get an infinite generator of the products of an iterable (e.g. for the iterable "ABC" it should return A, B, C, AA, AB, AC, BA, BB, BC, CA, CB, CC, AAA, AAB, AAC etc. ...
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2answers
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Permutation of given string

I am reading a book on DSA, and the author explains how to generate the permutation of strings using recursion. I want to know if there are better ways of doing the same, unless this is the best ...
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0answers
81 views

How to make python knapsack program faster

I have knapsack problem: I have data: List of product prices = MENU Most popluar product count = MOST_POPULAR_COCKTAIL Knapsack price = CASH Knapsack length = CHECK_LEN I need get all knapsack ...
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vote
1answer
134 views

How to make this algorithm faster?

It works fine, but it is slow. Could anybody help make this faster? ...
3
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2answers
274 views

Computing the number of permutations of n consecutive numbers

I'm just starting to learn C++ and have been experimenting with various functions. Here is one that computes the number of permutations of n consecutive numbers as well as all possible permutations ...
2
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1answer
259 views

Generating permutations with repetitions of string

I have written the below code which generates all possible permutations with repetitions of a string. I want to make this program shorter and much faster, but I don't know how to do that. ...
1
vote
1answer
81 views

Any way to optimize or improve this python combinations/subsets functions?

I believe this is essentially the same method as the itertools.combinations function, but is there any way to make this code more more perfect in terms of speed, ...
2
votes
2answers
195 views

multi-recursive replacement function

I wrote a function for creating all possible translations of a source string, based on a multiple translation map. It works, but generates a lot of intermediate maps (see line marked with *). Is there ...
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1answer
173 views

Discovering words from letters in Clojure (Letterpress Solver)

I created a Letterpress solver that will take a string of letters and return a list of valid words that can be constructer with the provided letters. Not all letters need to be used in each word. ...
2
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2answers
331 views

Print all interleavings of two given strings

Given two strings str1 and str2, write a function that prints all interleavings of the given two strings. You may assume that all characters in both strings are different Example: ...
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2answers
1k views

Print all permutations with repetition of characters

Given a string of length n, print all permutation of the given string. Repetition of characters is allowed. Print these permutations in lexicographically sorted order Examples: Input: AB ...
3
votes
1answer
398 views

Generating all subsets of a given set

I am learning Java Collections Framework. Can someone look at this code for generating all subsets of a given set and tell me any issues with it. ...
4
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1answer
222 views

compression condition permutation

I have 16 permutations each with 104 variables using the standard alphabet. The 104 variable permutation is selected based off of compression complexity. This is one example of the pattern I am able ...
5
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1answer
455 views

Pairwise Combinations Generator

Below is an algorithm to generate all pairwise combinations for a set of random variables. See here for an explanation of what constitutes a minimal all-pairs set. The algorithm below works but I feel ...
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2answers
11k views

Permutations of a list of numbers

I have written a program to find all the possible permutations of a given list of items. This precisely means that my program prints all possible P(n,r) values for r=0 to n. ...
5
votes
1answer
381 views

Enumerate k-combinations in Clojure (P26 from 99 problems)

I've been playing with Clojure for the last few evenings, going through the well known 99 problems (I'm using a set adapted for Scala). Problem 26 calls for a function that, given a set S and a no. ...
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3answers
495 views

Permutations Finder Help Number 2

I am that same eighth grader with the Java Application For Finding Permutations Efficiently question. I have changed quite a bit of code, and need some more help... ...
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5answers
7k views

Better way to generate all combinations?

I'm generating all combinations of an array, so for instance, ["a", "b", "c", "d"] will generate: ...
8
votes
1answer
365 views

Java application for finding permutations efficiently

I am an eighth grader with a school project of creating and application in Java that returns the total permutations of two given numbers. It needs to be light and efficient, for later deployment on a ...
2
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1answer
259 views

A combinatorial algorithm

How could I improve this algorithm? The goal is to organize matches between sport teams such that: Each team affront each other A minimum number of team should start a match after just finishing one ...
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2answers
2k views

Python generator function that yields combinations of elements in a sequence sorted by subset order

In Python, itertools.combinations yields combinations of elements in a sequence sorted by lexicographical order. In the course of solving certain math problems, I ...