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Questions tagged [set]

A set is a collection in which no element is repeated, which may be able to enumerate its elements according to an ordering criterion (an "ordered set") or retain no order (an "unordered set").

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LinkedHashSet Implementation

There's an implementation of LinkedHashSet in Java. Although this is limited with its functionality, it will do the basic job. I used interfaces so then I can use that interface for BST. Set ...
7
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1answer
510 views

Sort int array by frequency then value

Problem Take an array of ints as input and run a special sorting algorithm on it. This algorithm must first sort by int frequency, less frequent first, then sort by value. For example ...
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2answers
176 views

Data Structures for Counting Duplicates and using std::vector::erase

Problem Dupe detection for a vector of ints. I simply want a count of the unique input characters that occurred at least twice. The goal is to count a dupe only once and ignore that input character ...
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1answer
53 views

Possible letter combinations of a dial pad in linear time using a recursive approach

Time complexity: I walk the initial unzipped array of keys representing the number O(N) backwards. I then do an inner walk of the proceeding array of letters *O(L^2), mapping it to every value in the ...
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1answer
484 views

All subsets of a String in java using recursion

I wrote this code for printing all sets of a String. It also prints the empty subset. Is this the right approach ...
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2answers
277 views

Finding Repeat and missing numbers in an array

Problem Statement: You are given a read-only array of n integers from 1 to n. Each integer appears exactly once except A which appears twice and B which is missing. Return A and B. ...
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1answer
89 views

Grow-only set (CRDT)

I made up a quick and dirty implementation of the G-Set in C#. I was hoping for some feedback on my approach. I'm not totally happy with having the payload public but I can't see that I'm gaining ...
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2answers
912 views

From a set of words, output all words that fit a string of random letters (like Scrabble)

I am in my first year of programming with Python 3 and am wondering if anyone had a better way to program this problem. When the user provides up to 7 random letters as a single string, the program ...
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1answer
268 views

set implementation based on an array

I was supposed to implement set without using any implemented structures. I would love to know what can I correct in my code, because I am not that much satisfied with its quality, so if you have any ...
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2answers
38 views

Implementation of a shift operation for Set in JavaScript that emulates the one for arrays

I discovered that the JavaScript sets are ordered but don't offer a method to take the first element out of the set. For the arrays this operation exists and it's called shift. A very basic ...
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3answers
172 views

Finding the number of ways to partition {1,2, …, N} into p1 and p2 such that sum(p1) == sum(p2)

I am trying to write a space and time efficient algorithm to calculate the number of ways to partition a set of integers {1, 2, ..., N} into two partitions such that the sums of integers in the two ...
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1answer
104 views

Ruby Connected Components in a Graph

I've written the following code to find the connected components of a graph in ruby, but it is quite slow since I don't use any sensible data structure for the disjoint sets, and hence find_set is ...
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2answers
93 views

is_subset Python implementation

I wanted to ask for a code review for my implementation of Set: ...
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0answers
58 views

Sorted set a Queue

I needed a data structure offering both poll returning the smallest element and fast contains. A ...
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0answers
32 views

Benchmarking TreeSet in Java against a van Emde Boas tree based integer set

VanEmdeBoasTreeIntegerSet.java ...
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1answer
2k views

Concurrent HashSet

I've recently been using HashSet and locking on each method, I found this to not only be a lot of work (was using it in a lot of places) but I started to see inconsistency in my code. I later decided ...
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3answers
683 views

Finding common Integers between two lists

Write a method numInCommon that takes two Lists of integers as parameters and returns the number of unique integers that occur in both lists. Use one or more Sets as storage to help you solve this ...
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1answer
93 views

Python implementation for Set

I wanted to ask for a code review for my implementation of Set: ...
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3answers
82 views

Finding duplicates between n Sets

I have n Objects, Each Object has a Set of "nested" "Neighboring Objects". I need to check if there are duplicates between the "Neighboring Objects" Sets (there are no duplicates inside a single Set ...
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2answers
1k views
4
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1answer
3k views

Compute power set of a given set in Python

Problem: Given a set (let's say of integers), return the list of all of its subsets also known as the power set. It looks to be working, but I would like feedback on the algorithm and Python ...
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1answer
841 views

Thread safe tbb::concurrent_hash_map and std::set

I have a basic websocket server implemented in C++. I'm using Intel TBB's concurrent hash_map to store all the users, uniquely identified by the id. The concurrent ...
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1answer
211 views

Finding added keys, removed keys, and unchanged keys in ordereddict

I'm comparing two OrderedDict objects and I need to find added keys, removed keys, and keys that are present in both (the intersection). Sets are designed for ...
3
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1answer
85 views

Sorted vector/set class that works with simple types (char, int, double, etc…)

I'm new to C++ (approx. 3 months) and have just read Stroustrup's Programming Principles and Practice. Previously used Python a lot. As an exercise I tried to implement a custom container, with the ...
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1answer
61 views

Largest divisible subset optimization

So this is my solution to the following leetcode problem: https://leetcode.com/problems/largest-divisible-subset/description/ How could I optimize this code? I think the run time is \$\mathcal{O}(n^2)...
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4answers
4k views

Powerset (all subsets of a set) in Java

I am trying to get a powerset (all subsets of a set) in Java. So my logic for that is: A given set is one subset, so add so it as it is to result. Remove each element of set from given set and we ...
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2answers
128 views

Forming sets from pairs of numbers

I do not want to use a new data structure but the existing APIs in Java. Here's a solution. I am thinking if this can be made simpler. Input say ...
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3answers
236 views

Java Generics and ArrayLists

This abomination of code creates arrays based off input from the user. Sample input would be something like "S 4 aba bab baa aab" where: args[0] = array type (<...
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1answer
3k views

Set class with binary search tree implementation

Here is my Set implementation with binary search tree that compiles. Please let me know what changes are needed to make it better. Thank you. ...
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3answers
569 views

Monty hall python simulation

I have the following code that simulates the monty hall problem (see google for more details). I used sets to do it but is there a more intuitive or efficient way to do it? ...
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2answers
161 views

Set with custom compare

In my project I use std::set with custom Compare function for maintaining an event queue. It fulfills following criteria: event duplication is not allowed should ...
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2answers
6k views

Finding the intersection of elements in two sets

Is there another better way to implement those two methods in 1 and 2? Implement the method contains. contains returns ...
2
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1answer
39 views

A value set data structure for rapid statistics queries in Java - follow-up

(See the previous iteration.) Now all operations of the data structure work in exact constant time, yet it came with the price: the state of this set maybe non-sensical. A user may end up with the ...
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2answers
67 views

A value set data structure for rapid statistics queries in Java

(See the next iteration.) This question is an elaboration of my question. Just like the previous implementation, all operations (except clear) run in exact or ...
3
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1answer
474 views

Extract index of first unique element in large array in Swift

I'm using the following code to return the first index of a unique character in a large String. It works fine until I get to large strings, where it times out. Is ...
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1answer
6k views

Remove Duplicates from Array in Swift 3.0

I ran the following code through a Leetcode.com challenge and it says the runtime for the test cases is 119ms, which puts it at the back of the pack performance wise. The goal is to remove duplicates ...
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0answers
73 views

Spellchecker program is having issues due to vowel checking method

This program takes in a list of 275k or so words from '/usr/share/dict/words' and loads them into HashSet. It then takes in a list of 1000 words (taken from the dictionary and are scrambled (vowel ...
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1answer
257 views

Dictionary with ISet key as a collection of names

I'm writing a command-line utility and I need to find commands (and parameters) by name. The name can either be a full name like save or a shortcut ...
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2answers
920 views

Building a set of all subsets recursively in C++

Here is my recursive implementation of a power set function in C++. One thing that concerns me is that I am iterating over the set of sets while modifying its size. The code nevertheless functions as ...
5
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2answers
2k views

Determining if a relation is reflexive

A binary relation \$R\$ on a set \$A\$ is called reflexive if and only if \$R(a, a)\$ for every element \$a \in A\$. I want to know if there can be any improvements made on the function below to ...
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0answers
98 views

Substitute for `std::array::operator[]` in C++11 by using template-based recursion

What follows is a simplified version of a tentative implementation for a template-based set, named TemplateArgs. For the sake of clarity and focus on the question ...
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2answers
175 views

Find combination of sets which sum up to a specified result

Example input : A) 1, 2 B) 2, 8 C) 7, 8 Required Result : 8, 10 The output from the program with this input should be A + C. Few notes : We can only combine 2 sets. There must ...
3
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1answer
90 views

Return “support count” for a given itemset after searching a large list of transactions

Not having found a satisfactory association rules implementation in Python, I set out to code my own. The code below runs reasonably quickly, but the groceries dataset used for testing is peanuts ...
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2answers
664 views

Generate powerset in JS

I came across a mock interview question in which the candidate is asked to generate the powerset of a given set. The input set is represented as a unique array of integers. There was no solution ...
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1answer
642 views

Printing the power set of a given set of elements

Input: Set of elements (String) Output: Printing the elements of the power set of the given set ...
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3answers
724 views

Sorting a list by the modulus of 3

The input is an unsorted array of integers. The output should be an array of integers sorted based on the modulus of 3 (or any other number). It begins with all integers conforming to Integer % 3 == ...
2
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1answer
236 views

IEnumerable and Predicate sets in .NET

GitHub Repository Previously: Countable and uncountable sets in .NET (clean version). Thesis There is a full featured support of countable sets in .NET: ...
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0answers
69 views

Countable and uncountable sets in .NET (set operators, demo)

Up-to-date version: IEnumerable and Predicate Sets in .NET (Complete, Explained). Previously: Countable and uncountable sets in .NET (clean version). Disclaimer: Please do not interpret my attempts ...
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5answers
1k views

An ordered set in C#

I need a generic data structure that ensures that its elements are unique. C# has HashSet<T>, great! As it turns out, the elements have to stay in the order ...
2
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1answer
206 views

Countable and uncountable sets in .NET (clean version)

Sorry, it used to be some retired garbage in Countable and uncountable sets. Now and here it is clean. P.S. I would not like to say that this stuff is about to replace functional programming :) No, ...