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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.

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77 views

Binary Search Tree Implementation in C++17

I am a hobbyist computer programmer trying to learn modern C++ (in this case C++17). I thought it might be an interesting challenge to write a Binary Search Tree similar to ...
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0answers
65 views

Data structure that is fast to read and modify

I'm working on an apllication that needs to process a lot of objects in realtime. I've separated the logic from the UI so that it isn't as much of a mess. The basic idea is that every tick I'm trying ...
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0answers
48 views

Further dive into filtering using IPredicate

Preface This is a follow up to my previous post from not long time ago about containers and filtering. This post can be found here. Now, I will attempt to expand what I have learnt from the answer ...
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1answer
99 views

Class containers, filtering and coding practices

Context Usually, when I have to deal with a collection of items (especially objects) I tent to create a container class for that collection (wrapper?). What I mean by that is: when I have to handle ...
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3answers
74 views

My implementation of a for_each function that traverses a std::container by some step size integer N

As my answer to Iterating over an odd (even) elements only in a range-based loop, I wrote this function, with the following driver program and output: ...
2
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0answers
37 views

Simple generic macro-generated containers

In order to learn macros in C I decided to make a generic data structures generator for other projects that I have in C. The main macros are the following: ...
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0answers
16 views

Extension to BindingList<T> that allows for cancelable notifications of changing and deleting

This is an extension of the System.ComponentModel.BindingList<T> class that allows for notifications of item changing and deleting. These notifications ...
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3answers
499 views

Pass IEnumerable<T> as an argument of method and repository pattern

I've seen tutorials of Unit Testing and I've never seen that IEnumerable<T> used as an argument of method. All authors use ...
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1answer
90 views

java.util.Set extension/implementation

Lately, I was working on some experimental java.util.Set extension, IdSet: ...
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1answer
54 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
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2answers
853 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
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1answer
118 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
467 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. ...
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3answers
107 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 ...
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4answers
746 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
579 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
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1answer
50 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 ...
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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
278 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 ...
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2answers
293 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
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1answer
55 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
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2answers
132 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
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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 ...
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3answers
156 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 ...
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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 ...
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2answers
205 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
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2answers
231 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
85 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 ...
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2answers
62 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
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1answer
172 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
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3answers
82 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
140 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
69 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
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0answers
114 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
302 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 ...
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1answer
677 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 ...
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2answers
1k 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
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1answer
106 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 ...
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1answer
42 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 ...
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2answers
361 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. ...
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vote
1answer
341 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
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1answer
55 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
41 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 ...
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2answers
72 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 ...
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0answers
1k 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
505 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
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1answer
10k 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
67 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
452 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 ...