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

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3
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3answers
103 views

Another permutator

This is a solution to this problem. The problem statement: write a program to display all possible permutations of a given input string--if the string contains duplicate characters, you may have ...
2
votes
1answer
20 views

Generating Cartesian product of strings in R

Sometimes I need to create character vectors like this one: ...
5
votes
2answers
81 views

Binomial coefficient

I wrote a C++ function to calculate the binomial coefficient, trying to avoid overflows as much as possible. ...
5
votes
2answers
65 views

Possible combinations following a rule

The problem is the following: We have a number of months to buy a number of supplies. The sooner we finish buying them, the better, but we don't know how much we can buy per month and would like to ...
4
votes
1answer
61 views

Seeking improved Objective-C permutation algorithm

This algorithm seeks to find all of the possible permutations of a word: ...
9
votes
3answers
181 views

Generate all possible combinations of letters in a word

This is a JavaScript function that returns ALL the possible combinations of whatever word the user enters. I am looking to clean this code up a bit...any and all suggestions are welcome! ...
4
votes
1answer
64 views

Permutations program in Python

This code asks for letters and a number of letters per word and generates all possible permutations. Then compares those permutations with an English dictionary and creates a list with all the words ...
3
votes
1answer
81 views

Finding the 'Minimum' AND of all the possible subsets of a set

The subset size should be greater than or equal to 2. How can I speed up this code? ...
8
votes
1answer
85 views

Verifying boardgame mathematics with MATLAB

I recently bought this math-based boardgame for my little cousins, and am now trying to verify its design with some MATLAB code. The relevant parts of the game are: A board with numbers from 1 to ...
21
votes
3answers
370 views

Analyzing Minesweeper Probabilities

Calculating probabilities in Minesweeper might sound like an easy task, but I've seen so many probability calculators that's either incorrect, horribly slow, or with ugly code (or all of them) so I ...
6
votes
5answers
528 views

Improving efficiency of Project Euler 185 (16-place Mastermind)

This a solution for Project Euler Problem 185. It works fine for the example but slow for the problem statement. How can I improve its speed and efficiency? ...
3
votes
2answers
179 views

Calculate all possible combinations of an array of arrays or strings

I'm using code adapted from this Stack Overflow question to calculate all possible combinations from an array, which may contains strings. For example: ...
12
votes
7answers
2k views

Is my solution to return kth row of the Pascal's triangle suitable for a job interview?

Question: Given an index \$k\$, return the \$k\$th row of the Pascal's triangle. For example, given \$k = 3\$, return \$[1,3,3,1]\$. Bonus points for using \$O(k)\$ space. Can it be ...
6
votes
3answers
317 views

Get distinct combinations of numbers

The below code returns all distinct combinations based on the logic that 1,2,3 = 3,2,1 = 2,3,1, so it only returns 1 instance of that set of numbers. ...
1
vote
1answer
45 views

Find triangles from line

I have some lines that form triangles. I'd like to challenge the fastest way to find all triangles. In particular the code should take an ArrayList of Line2D object and return an ArrayList of ...
7
votes
2answers
78 views

Simplified Bin Packing using JavaScript

This code determines the maximum number of boxes (one size) that can fit into the back of a truck, checking all possible orientations to ensure maximum Bin Packing excitement. This is (hopefully) the ...
6
votes
1answer
137 views

Given a shape, return all triangles that can be formed

Given a shape, get all triangles that can be possible by connecting the points. Example: given 3 points, only 1 triangle is possible, but given a pentagon, 10 are possible. Also the ...
3
votes
4answers
125 views

Better way to achieve looped output result

I have 4 variables - say A, B, C and D Each variable can have 4 values - say 1, 2, 3 and 4 I need to generate all possible combinations of values Example of Expected Output: ...
3
votes
3answers
66 views

Curious fractions in functional Ruby

Problem 33 in Project Euler asks: The fraction 49/98 is a curious fraction, as an inexperienced mathematician in attempting to simplify it may incorrectly believe that 49/98 = 4/8, which is ...
7
votes
1answer
101 views

Speeding up subset sum implementation

Important fact: the number of the input is greater than 1. How do I use this fact to speed up this solution? ...
7
votes
3answers
211 views

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
votes
1answer
71 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 ...
10
votes
2answers
130 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
votes
1answer
94 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 ...
4
votes
0answers
269 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
votes
2answers
134 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 ...
4
votes
3answers
291 views

Prints out all ways to multiply smaller integers that equal the original number

Write a program in Java that takes a positive integer and prints out all ways to multiply smaller integers that equal the original number, without repeating sets of factors. In other words, if ...
1
vote
0answers
60 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
votes
1answer
113 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
votes
2answers
534 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 ...
1
vote
3answers
3k 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
votes
2answers
166 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
votes
1answer
227 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
votes
3answers
2k 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
votes
1answer
372 views

Fastest way for working with itertools.combinations

I need to speed up the function below: ...
2
votes
1answer
48 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
votes
2answers
116 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
126 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
votes
2answers
143 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
votes
3answers
170 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
votes
2answers
105 views

Integer Partition

The aim is to enumerate all possible sets of whole numbers whose sum is a given integer. ...
3
votes
1answer
91 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 ...
20
votes
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 ...
8
votes
1answer
6k 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
vote
1answer
65 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 ...
3
votes
0answers
48 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 ...
3
votes
0answers
591 views

Ugly numbers problem

Taken from one of codeeval.com challenges: Challenge Description: Credits: This challenge has appeared in a Google competition before. Once upon a time in a strange situation, people ...
3
votes
2answers
187 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 embarrassingly parallel problem I decided to use ...
3
votes
1answer
135 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
votes
1answer
195 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. ...