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Questions tagged [collections]

Collections APIs provide developers with a set of classes and interfaces that makes it easier to handle collections of objects.

0
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1answer
44 views

Breaking a 32-bit value into bytes for an ArrayList

I am very new to Java and its collections and I'm trying to figure out "best" way to populate an ArrayList<Byte> in Java. In particular, I'm trying to take a ...
4
votes
2answers
840 views

Going from IQueryable<IEnumerable<myObj>> to IEnumerable<myObj>

I have a "GetPersonsPerDepartment()" method returning a IQueryable<IEnumerable<Person>> while I'm trying to get a simple ...
4
votes
1answer
116 views

Collections management with many derived elements

I've been told few days ago that using is is a code smell and anti-pattern. I used it in an game to filter some elements of a collection (the inventory of the ...
3
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2answers
109 views

Ring Buffer Implementation in C++14

A ring buffer or circular buffer is a fixed sized queue that advances head and tail pointers in a modulo manner rather than moving the data. Ring buffers are often used in embedded computer design. ...
4
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3answers
104 views

Really easy synchronised access to an IEnumerable without boilerplate code

Often when reading data from a sequence (IEnumerable<T>) in multi-threaded code, a consistent snapshot needs to be taken inside a ...
8
votes
4answers
729 views

Alternating items in a collection

Is there any better way how to mix items in list? In my example: I want to sort list items as male, female, male, ... My solution is probably very time and resource demanding. Can I do it somehow with ...
6
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2answers
546 views

Moving elements satisfying a predicate from one container to another

I've implemented a C++ algorithm that moves elements satisfying a given unary predicate from one container into the other, deleting them from the input container. This is my implementation: ...
3
votes
1answer
49 views

Time series dataset with temporally enforced object lifetime

The purpose of this class is to have that can maintain data set where the samples contained within the set have an expiry time. Samples are inserted in chronological order. In an attempt to memory ...
2
votes
0answers
19 views

How to connect a propery class/object with a collection (its database class)?

I'm struggling with organizing my code regarding 'best practise'. In particular how I link a class with its collection class. I've 2 classes: ...
6
votes
1answer
191 views

Generic Skip list implementation in C++ Version 3

This is a follow up of Non generic Skip List implementation in C++ Version 2 If you don't know what a Skip list is: https://en.wikipedia.org/wiki/Skip_list I tried to incorporate as much ...
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0answers
30 views

Dependancy Container

I'm currently creating my own microframework for learning purpose and I want to make it more powerful by providing a way to register classes and instantiate them (once) only when needed. So here is my ...
3
votes
2answers
255 views

Non generic Skip List implementation in C++ Version 2

Edit: This code was reworked and repostetd under a new question: Generic Skip list implementation in C++ Version 3 This is a follow up of: Non generic Skip List implementation in C++ If you don't ...
4
votes
1answer
54 views

General use multi-dimensional container using operator[]

This is a followup to a previous question of mine on same subject. Context I want to have a tool that allows to simulate as much as possible a C++ standard container for a multidimensional ...
4
votes
2answers
121 views

Non generic Skip List implementation in C++

Edit: This code was reworked and repostetd under a new question: Non generic Skip List implementation in C++ Version 2 To sharpen my C++ skills I tried to implement a skip list. I was quite happy ...
2
votes
2answers
76 views

Summing payments by year using Java Streams

I'm using 1.8.0_162 version of Java and here is my task about stream framework ...
8
votes
3answers
155 views

Build clusters from connections (virus propagation)

The scenario is the following: There is a list of persons and places where those persons visit. Each person is connected to a single or multiple places. See the picture below, where O[i] represents ...
4
votes
3answers
107 views

List mapping of large data set from file

I have a list of items 116 thousand and my mapping function is taking quite some time to process. I am using the file helpers library to write the CSV to disk but its the for each that is taking ...
9
votes
2answers
191 views

Multi-dimensional container using operator[]

This is a late followup to a previous question of mine on same subject. Context: I want to have a tool that allows to use all the C++ goodies (algorithms, for loop on containers, etc.) on a ...
2
votes
2answers
159 views

Wrapper for a raw array so that it can be passed to templates expecting Standard Library containers

I am working with a code base where unfortunately I cannot replace all raw arrays with std::array. The spec provides no guarantee that the memory layout of a ...
7
votes
1answer
79 views

Custom container for iterating over combinations of elements from multiple sets

Motivated by some SO quesitons [1, 2] I made an attempt at implementing a custom container with a bi-directional custom iterator for iterating over all combinations of elements from multiple sets. I ...
0
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0answers
36 views

Achieving a synced collection of objects with NHibernate

I'm working on a WinForms application that can modify objects loaded from a MSSQL server (using NHibernate). I need to load the entities into a DataGridView, and ...
5
votes
2answers
61 views

Filter queries three orders of magnitude slower than insertions

As part of a C++ library, I'm implementing a filter class for approximate set membership and abundance queries. The filter has two primary operations: ...
4
votes
1answer
149 views

Fast insert unique container

I posted the same question at StackOverflow then I got an advice to post it here. Original question: https://stackoverflow.com/questions/49998297/fast-insert-unique-container I have to store ...
3
votes
3answers
81 views

Fill in workbook with data from another workbook

Followup to this question I made a macro that will fill in data in a workbook that has 65 (24 are user filled) columns and can go as long as 1500 rows. The macro can import about 1500 rows and 24 ...
3
votes
1answer
134 views

Finding the lowest possible number of changes to turn one string into another

I've been working on a task: I have two giant strings, both consist of the same characters just scrambled (both consist only capital english letters). The task is to find the lowest possible number of ...
4
votes
1answer
67 views

Fill a new Workbook with info from another workbook

I made a macro that will fill in data in a workbook that has 65 (24 are user filled) columns and can go as long as 1500 rows. In an ideal scenario, the workbook has a perfect column that could work ...
4
votes
0answers
112 views

C++11 Removable connection from emitter or receiver object

Please review my solution for the following problem. I am interested in: Maintainability Usability Logical correctness Efficiency Problem: It has 1+ objects each in separated thread and between the ...
4
votes
1answer
172 views

Complete ObservableDictionary

In conjunction with a recent question of mine, I found that an ObservableDictionary would be very handy for my situation, so I decided to implement one. I've ...
1
vote
1answer
614 views

Set, List and Map equality comparison with Lambda check

I'd like to be able to compare two objects with different equality checks. This should work if they're in a Set, List or ...
3
votes
2answers
895 views

Example of adding STL iterator support to custom collection class

I'm trying to create an example of a custom collection with an API meeting the requirements of STL iterator templates, as a learning experience. The collection used here, a ring buffer, is merely a ...
5
votes
1answer
104 views

C++ container — variable byte coded numbers list

I'm writing a container for unsigned integers, which uses variable byte coding. It works but some decisions I took look ugly so I would be glad if you gave me some hints for improving the design. I ...
0
votes
1answer
41 views

Create numerical-key array from existing string-key array, with a given string-key as first item

I have an array of available languages for my website, with a short ISO country code as the key for each language. I need to create a new array that contains the same info, but with numerical keys and ...
6
votes
2answers
243 views

Iterator of Container of Container

Based on this question I though I would pull together an iterator that iterated over a container of containers. ...
1
vote
1answer
259 views

Returning containers from function - C++ [closed]

I've been trying to implement a few interfaces for processing data. And most of the time I do new of container and return a smart pointer to this container. ...
3
votes
1answer
54 views

Python JIT container type

This is a follow on from this review. Where I am attempting to improve the performance of my rest client. I have created an container type (as suggested in my previous post) that lazily instantiates ...
0
votes
1answer
40 views

Find combinations of items in a nested collection

It's a very typical problem that I come across here and there. Imagine that you have a collection of items of any type, and sometimes items are collections themselves; you then need to "expand" them ...
1
vote
2answers
69 views

Given a list containing dates and the amount spent on each date, display the total amount spent per month

I had an interview yesterday where I was asked to write a function that would take in a list containing a date and the amount of money spent on that date, and to output the total amount spent per ...
1
vote
0answers
953 views

Custom dictionary class for reading and writing json value to a file

Is my implementation good? The program works as planned, but I wonder if some parts of the code can be made cleaner or more efficient. The file output looks like this: ...
0
votes
1answer
414 views

Scala type matching map

I was working with some complicated generics system, and I found the need to make an abstraction for a typesafe mapping between K[T] and V[T] where T is the same for individual pairs. In the case ...
4
votes
1answer
8k views

Map with case insensitive get, remove and containsKey

I am looking for a Map implementation (with String keys and any generic type for values) that would support getting, removing ...
2
votes
1answer
65 views

Getting single element or throwing one of two exceptions

Sometimes I need to get a single thing from a collection but I'm not very happy with the Single extension. It does not differentiate between empty and more than one ...
2
votes
1answer
412 views

VBA: Loop all .xlsx files in a folder and produce a list of worksheets and workbooks contained therein

I pieced together this code in answer to the following OP post on Stack Overflow: Get worksheet Names of All .xlsx files in a folder Task: The OP basically wanted to loop all .xlsx files in a folder ...
2
votes
2answers
105 views

Vector replacer

I rolled an own vector-like construct with improved performance and got it reviewed. Here is the updated version. ...
2
votes
1answer
990 views

Vector-like custom container with improved insert performance

I rolled a little container class (just for couriosity) which was meant to be able as a vector replacement in some cases. (Whoever wonders about the lack of move semantic etc, I just left it out due ...
5
votes
2answers
175 views

General FizzBuzz in Scala

I wanted to create a FizzBuzz implementation that both showcases the strengths of Scala (Functional paradigm and collections) and is general enough to anticipate the typical interview follow-up ...
1
vote
1answer
133 views

Array Wrapper Class

I’ve wrote a small array wrapper class which mimics the built-in Collection for adding and retrieving items. Once the object is created, you set the array capacity and that would not change. ...
2
votes
2answers
106 views

Optimise many namedtuple assignment statements [closed]

I'd just like to know if there's a way I can reduce the number of namedtuple assignment statements in the code below. The actual program has over 60 assignment ...
1
vote
1answer
2k views

Generic Comparator

I have tried to make a generic comparator with the use of reflection, but I am not sure how efficient it is or if it is the right way to do so Also, I don't know how it will handle dates. ...
1
vote
2answers
83 views

PHP port of Java collections

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2
votes
0answers
342 views

Flattening a map into a list of records

In my everyday work I'm trying to move away from traditional iterating over collections to a more Java 8 streams-like behavior. I'm currently working on a project where I have a collection defined as: ...