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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.

8
votes
4answers
696 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
votes
2answers
536 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: ...
0
votes
0answers
19 views

Loop each items are the unique solution to retreive one specific property from one collection object?

with this code I add item/properties into my collection: ...
0
votes
0answers
38 views

Scala function to summarize sales metrics

I have a Java background and have recently started learning Scala. I've implemented a method that still looks to me more like a Java style. How can it be improved using various Scala features to be ...
3
votes
1answer
47 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
136 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 ...
1
vote
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
222 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
108 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
106 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
176 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
126 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
74 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
votes
0answers
34 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
59 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
132 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
132 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
65 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
132 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
436 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
462 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
102 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
39 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
171 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
187 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
37 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
719 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
340 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 ...
3
votes
1answer
6k 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
63 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
357 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
98 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
830 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
166 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
123 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
100 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
1k 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
82 views

PHP port of Java collections

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2
votes
0answers
283 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: ...
2
votes
1answer
109 views

Implementing an HotelManager interface in Java

Got a mission to implement an Hotel Manager interface. I will post the interface and the attached class Reservation, and will add my code. What I am asking you is ...
2
votes
1answer
335 views

Filtering a log file and extracts by different properties

I have implemented a program to extract a log file which contains a header line, followed by zero or more data lines, in comma-separated value format. The file consists of 3 columns. The first column ...
0
votes
2answers
25 views

Removing objects from a list that don't appear in a list of ID's

I have a list of objects with each of them having an ID. I have a second list that is just a list of media ID's. I want to remove the objects from the first list that don't match a mediaID contained ...