Combinatorics is a branch of mathematics concerning the study of finite or countable discrete structures.
3
votes
2answers
41 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
83 views
7
votes
3answers
193 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
69 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
votes
2answers
92 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
70 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
votes
0answers
197 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
123 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
vote
0answers
50 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
107 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
224 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
2answers
656 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
142 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
154 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
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
votes
1answer
223 views
2
votes
1answer
40 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
103 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
votes
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
votes
3answers
155 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
101 views
Integer Partition
The aim is to enumerate all possible sets of whole numbers whose sum is a given integer.
...
3
votes
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 ...
18
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 ...
6
votes
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
vote
1answer
62 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
43 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
votes
1answer
396 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.
...
3
votes
2answers
167 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
votes
1answer
114 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
171 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.
...
6
votes
2answers
1k views
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 ...
1
vote
0answers
85 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 ...
1
vote
1answer
134 views
How to make this algorithm faster?
It works fine, but it is slow.
Could anybody help make this faster?
...
3
votes
2answers
279 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
votes
1answer
265 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
201 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 ...
1
vote
1answer
174 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
votes
2answers
340 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:
...
10
votes
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
433 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
votes
1answer
224 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
votes
1answer
464 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 ...
6
votes
2answers
12k 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
383 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. ...
2
votes
3answers
497 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...
...
17
votes
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
371 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
votes
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
...
