Combinatorics is a branch of mathematics concerning the study of finite or countable discrete structures.
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41 views
SPOJ - Alphacode - Exceeds Time Limit
I'm trying to solve Alphacode on SPOJ. The challenge is to count the ways to split a string of up to 5000 digits into a sequence of numbers, each ranging from 1 to 26.
It works fine for small ...
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1answer
37 views
Iterative “counting change” implementation in mit-scheme
Here is my iterative implementation of the Counting change example in SICP. Please note that I'm a beginner, which means I only know the basic syntax for the time being.
Requirement:
How many ...
5
votes
2answers
134 views
Calculating the count of integer partitions of a number (uses stateful vectors internally)
I've written a Haskell function to count the number of partitions of an integer - it's basically an implementation of the same algorithm as this one, using Euler's Pentagonal Number Theorem:
$$P(n) = ...
3
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2answers
62 views
Equivalents permutations function
My function is supposed to essentially give the cartesian product of all the letters in a string with the caveat that you have to give the permutations of every equivalent of each character in a ...
2
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1answer
74 views
Producing residues of combinatorics on strings
Basically, this code does multiplication of chosen operations.
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2
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0answers
60 views
Generating all unique permutations of a string
Here is a plan for generating the permutations of S: For each item x
in S, recursively generate the sequence of permutations of S - x, and
adjoin x to the front of each one. This yields, for each ...
0
votes
1answer
63 views
All permutations of integer vector
I have spent a decent amount of (waaay too much) time trying to write the below function and get my head around recursion. The aim was to return all permutations of an int vector (assuming no ...
0
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0answers
76 views
All combination of character alphabet
I write this code to find all combination of an alphabet z={A,B,C...N}.
In DNA case,we use z={A,C,T,G},then the function Words and ...
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2answers
97 views
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1answer
102 views
Subset sum simple iterative implementation
Here is the simplest iterative implementation of Subset sum problem that I could come up with1, as a follow up to this recursive implementation of the same problem:
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2answers
210 views
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1answer
89 views
Iterative implementation of K of N variations
Objective:
Print all combinations with repetition of k elements out of a set of n elements.
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3
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1answer
57 views
Compute the mean, variance and standard deviation of all pairs, triplets and sets of four
My code sample for finding the mean for the case of pairs is:
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3
votes
1answer
59 views
Calculating how similar two objects are according to a database
I want to calculate how similar two objects are according to a database. However the code is very slow; it takes around 2 minutes to analyze just 3 objects. How can I speed it up? I have tried to ...
1
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1answer
78 views
Using brute force to do large scale permutations and combinations
This problem should self explanatory based on namings of variables and functions. In essence I am doing well over 720*720*90 checks/calculations. Hence, this is taking far, far too long. How do I make ...
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1answer
64 views
Efficient String permutations calculation in Java
In trying to compute permutations of a given String, what can I do to further improve the code below for memory and/or time efficiency?
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2answers
42 views
Pascal's triangle with libgmp and pthread in C
I have written a program to generate a pascal triangle of predefined size.
Code
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2
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1answer
28 views
Shortest code to generate a full mesh of elements
I am trying to find the shortest code that generates a full mesh of the elements fed into it in graphviz format
e.g. the full mesh of [0, 1, 2] is:
2 -> 0
2 -> 1
1 -> 0
I have the code below and I ...
1
vote
0answers
53 views
Recursively generate combinations while using Boost Coroutines
I've tried out implementing a combination generator using boost coroutines. It accepts an array of possible values and generates one array at a time for each combination. As a limitation, it only ...
4
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1answer
51 views
Permutation index Python
Here is my Python code for finding the permutation index of a given digits and a target number. And by permutation index I mean, for example, given digits ...
2
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0answers
43 views
Calculate and plot expected value involving summations and products
I wrote a code to calculate a series of summations and products for a maths assignment I'm doing. The equation is shown below.
$$E(\sigma)=[1-(P(\text{$1^{st}$ rejects}) \times P(\text{$2^{nd}$ ...
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1answer
144 views
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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3answers
107 views
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 ...
4
votes
1answer
84 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), (...
2
votes
1answer
126 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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1answer
60 views
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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3answers
2k views
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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1answer
136 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 ...
2
votes
1answer
83 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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1answer
37 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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0answers
74 views
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 ...
5
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0answers
42 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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0answers
192 views
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2answers
75 views
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\},...
2
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1answer
87 views
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 ...
2
votes
1answer
225 views
2
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1answer
125 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 ...
3
votes
1answer
329 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 ...
9
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2answers
163 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 ...
5
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2answers
571 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[].
...
9
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5answers
275 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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1answer
61 views
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1answer
98 views
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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1answer
116 views
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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5
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1answer
263 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 ...
6
votes
3answers
145 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 ...
2
votes
1answer
260 views
5
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2answers
160 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 ...
3
votes
1answer
72 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 ...
6
votes
1answer
70 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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