Questions tagged [combinatorics]
Combinatorics is a branch of mathematics concerning the study of finite or countable discrete structures.
418
questions
1
vote
2answers
81 views
MaxProductOfThree in C#
This is my solution for the MaxProductOfThree from codility, it scores 100%, but I'm not a fan of the if if if structure it has going on.
Task description
...
7
votes
2answers
123 views
Letter Combinations of a phone number using a Dictionary
Problem statement (online source)
Given a digit string, return all possible letter combinations that the
number could represent.
A mapping of digit to letters (just like on the telephone ...
11
votes
1answer
112 views
Recursive code to generate a parametric sweep of input values
I generate a set of data based off every combination of inputs. The source range that's inputs requires headers to identify the parameters. In its present state I'm not content as it's not as ...
9
votes
1answer
262 views
Earliest time frog can jump to the other side of a river in C#. Codility's task
I'm new to C#, I programmed a little in java in the past.I had the two previous exercises reviewed here (permCheck, cyclicRotation, with a 100% score, just like this one), and I'm applying what the ...
6
votes
2answers
185 views
Codility's Permutation Check in C#
I've made a few things in Java, and now I'm learning C#.
The code passes the tests with 100% final score. I want to know what things can be improved in my code.
Task description
A non-empty ...
4
votes
1answer
57 views
Go function to generate permutations of a given integer array
I'm writing a function to generate a permutation of given []int:
...
2
votes
2answers
122 views
Counting block combinations I: Project Euler 114
Problem statement (For more detailed description (including pictures), please, visit the link):
A row measuring seven units in length has red blocks with a minimum
length of three units placed on ...
4
votes
1answer
76 views
Counting Bouncy Numbers: Project Euler #113
Problem statement:
Working from left-to-right if no digit is exceeded by the digit to its
left it is called an increasing number; for example, 134468.
Similarly if no digit is exceeded by ...
2
votes
3answers
88 views
Mapping words to letters which contains
Given sentence for example: ala ma kota, kot koduje w Javie kota I should to every letter occurring in the sentence I should map every string that this letter ...
2
votes
3answers
109 views
Counting numbers that are divisible by 3 and can be produced from the digits of a given number
I'm trying to solve this problem from codewars.
Problem
Given a certain number, how many multiples of three could you obtain with its digits? Suppose that you have the number ...
6
votes
4answers
1k views
LINQ for generating all possible permutations
Permutate() is supposed to generate all possible permutations of the source sequence:
...
3
votes
2answers
63 views
Fixed Content Necklace Generator
I wrote a class that generates combinatorial necklaces with fixed content as per Sawada: A fast algorithm to generate necklaces with fixed content. The class is instantiated with an input list that ...
11
votes
3answers
401 views
Print sums of all subsets
Print sums of all subsets of a given set
Problem summary : Print all subset sums of a given set of integers
My approach is to store previous results and use them to calculate new (similar idea as ...
3
votes
2answers
127 views
Challenge: phone keypad to letters - return all possible strings
The challenge:
Given a mapping of digits to letters (as in a phone number), and a digit string, return all possible letters the number could represent. You can assume each valid number in the ...
2
votes
2answers
55 views
Project Euler # 24 Lexicographic permutations in Python
A permutation is an ordered arrangement of objects. For example, 3124 is one possible permutation of
the digits 1, 2, 3 and 4. If all of the permutations are listed numerically or alphabetically, we ...
4
votes
2answers
120 views
Letter case permutation
The question can be found here https://leetcode.com/problems/letter-case-permutation
Given a string S, we can transform every letter individually to be
lowercase or uppercase to create another ...
2
votes
2answers
112 views
Staircase challenge - Python
Your task is to print all unique ways to climb a staircase of length n where, from each step, you can take steps of size x where ...
6
votes
1answer
89 views
A straightforward method for computing the Binomial probability mass function
I've been writing up code to test an alternate way of calculating the Binomial probability mass function. The Binomial random variable is the number of heads out of N coin tosses with coins that have ...
4
votes
2answers
79 views
Array of all permutations in C
Is this a good compromise between readability and verbosity? Are there any bugs, additional error checking, or extraneous code as well?
...
11
votes
6answers
2k views
HackerRank: Electronics Shop
Challenge from Hacker Rank -
Monica wants to buy a keyboard and a USB drive from her favorite electronics store. The store has several models of each. Monica wants to spend as much as possible for ...
7
votes
5answers
202 views
String combinations of 0 and 1
I was asked this question in an interview:
Given a string s consisting of 0, 1 and ...
6
votes
2answers
146 views
Sums of all sublists
The parts_sums function in the code takes a list as parameter and then returns sum of all sub-lists present in the list. e.g.
if, ...
4
votes
1answer
120 views
Pick the best combination of n choose k models
Algorithm
Let \$M_0\$ denote the null model which contains no predictors. This model simply predicts the sample mean of each observation.
For \$k=1,2,\ldots,n\$:
Fit all \$n \choose k\...
4
votes
3answers
403 views
Generate parentheses solution
I have coded a solution to build all valid permutations of parentheses.
My code is below.
I have a question on my code based on a comment by my PEP8 checker. It said that there was no need to ...
4
votes
1answer
83 views
Generate all possible combination of n-pair parentheses
The task is taken from LeetCode
Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.
For example, given n = 3, a solution set is:
...
2
votes
1answer
50 views
Computing the cost for creating a perfect square (with N = 3)
You are given a square matrix \$A \in \mathbb{ N}^{n,n}\$, this number contains integers from \$1\$ to \$n^2\$. The task is to compute the minimal cost, to change this square into a perfect square. A ...
3
votes
1answer
123 views
Swift function to find a specific set of combinations of 3 digits within a larger integer array
I asked this question on Stack Overflow and was directed here. I'm working on a function that will help me quickly find all the upper structure triads (3-note chord) that I can add to a 4-note 7th ...
4
votes
1answer
353 views
Project Euler 76: Counting summations
Project Euler Problem 76 asks:
How many different ways can one hundred be written as a sum of at least two positive integers?
My code is correct but just works slowly.
...
2
votes
0answers
30 views
Interleave two lists, preserving the order of elements in their original list
I need to write an OCaml program that return all possible zip of two lists together while preserving the order of the element in each list. For example, if we zip the lists [1;2] and [3;4], we get [[1;...
3
votes
1answer
52 views
Iterative version of a permutations algorithm
For learning purposes, I've written an iterative version of a recursive algorithm for generating the set of permutations for a given set of unique integers.
Can I make any improvements to increase ...
7
votes
2answers
572 views
Compute all the permutations for a given vector of integers
The task is to compute all the permutations for a given vector of integers (but of course the specific integer type is not relevant for the solution)
The strategy is based on recursion + iterations
...
1
vote
2answers
79 views
Leetcode Next Permutation in Python
My solution to Leetcode Next Permutation in Python.
Implement next permutation, which rearranges numbers into the lexicographically next greater permutation of numbers.
If such arrangement is ...
2
votes
2answers
104 views
Iteratively generating permutations with repetitions
I tried to solve the simple problem of generating all permutations of length n with m distinct elements where repetition is allowed. Doing this recursively took me like 10 minutes:
...
5
votes
1answer
232 views
Best way to performance permutations
This has been my white whale for a while, the idea is convert all the symbols to the goal symbol using all the pieces.
I did an algorithm like 5 years ago (now is lost) and reach lvl 48 but got stuck ...
3
votes
2answers
106 views
Number of possible numbers in roman number string
I just started learning programming a few months ago, and I'm intrigued by Haskell. To learn a bit I tried to adapt some code I have in Java so I can see what are equivalent solutions in Haskell.
The ...
1
vote
0answers
52 views
itertools.produce reduced and filtered
I need to generate list of all allowable test combination values of of actor, action and ...
4
votes
2answers
263 views
PermCheck Codility
The following code gets 100% on the PermCheck task on Codility. It should be O(N).
The question is:
A non-empty array A consisting of N integers is given.
A permutation is a sequence ...
5
votes
5answers
791 views
Checking if an integer permutation is cyclic in Java
A an integer permutation array[] is said to be cyclic if and only if we can choose an arbitrary element at position i, move it ...
4
votes
1answer
74 views
Iterating over combinations
Background
The following describes the real world problem that my code is intended to solve. It is may help you understand what the code is doing and why. I don't think this is strictly necessary in ...
3
votes
2answers
255 views
Grid search parameter combinations in Python
For a computation engineering model, I want to do a grid search for all feasible parameter combinations. Each parameter has a certain possibility range, e.g. (0 … 100) and the parameter combination ...
2
votes
1answer
53 views
Worker placement in Orleans board game/combinations
I am trying to program the board game Orleans. I am planning on making a computer player that plays randomly at first. The part of the game that I'm struggling to code elegantly at the moment has to ...
2
votes
3answers
241 views
Generate all possible permutations of a string in C++
This is my version of the possible permutations of a string challenge. Please give me feedback or criticism. There are two vectors here: positions and ...
1
vote
1answer
57 views
Find the combination of matches which are closest to each other
Problem - Given three sorted arrays find combinations which are closest to each other.
example -
...
2
votes
3answers
88 views
Counting paths between 3 cities in C++
The task is to make a program that prints out how many possible paths a driver can use to visit three cities so that he visits each city exactly n times. The program must be executed within 1 minute ...
3
votes
2answers
429 views
Print out all possible letter combinations a given phone number can represent
I am working on a problem in which given a 7 digit telephone number, we need to print out all possible combinations of letters that each number could represent.
I came up with below code and I was ...
6
votes
1answer
60 views
General nested for
I needed a general-purpose function that accepts some sequence_container<sequence_container<T>> and iterates all permutations of the inner container. To ...
1
vote
1answer
93 views
Python finding next word permutation with function generator
Learning how to use function generators in Python I practiced with the following code that finds the next permutation of a word and then uses this new word as input for the next one until there are no ...
5
votes
2answers
417 views
Finding all possible letter combinations from an inputted phone number
Prompt:
Given a string containing digits from 2-9 inclusive, return all
possible letter combinations that the number could represent.
A mapping of digit to letters (just like on the ...
9
votes
2answers
2k views
Generating the powerset in C
I am solving another problem in leetcode.
Given a set, generate all the subsets of the set.
Input: [1,2,3]
Output: ...
2
votes
2answers
528 views
Generating all permutations of 1 digit, 2 equal letters and 2 different letters efficiently
I created a function that generates all the combinations of 1 digit, 2 equal letters and 2 different letters.
I reduced the numbers and letters to make it more easy to calculate:
...
