What collections did you use in your solution (HashMap and ArrayList) and what role does each play?

In a solution using Flutter, I used two main collections: HashMap and ArrayList.

• HashMap is a data structure that stores key-value pairs. It provides quick access to elements by key, which is convenient for storing and searching data, such as settings or cached objects.

• ArrayList is a dynamic array that allows storing an ordered list of elements with fast access by index and dynamic resizing. It is used for storing sequences of data, such as a list of interface elements or data to be displayed.

Example of usage in Dart (Flutter):

import 'dart:collection';

void main() {
  // HashMap for storing settings
  var settings = HashMap<String, String>();
  settings['theme'] = 'dark';
  settings['language'] = 'ru';

  // ArrayList equivalent — List in Dart
  List<String> items = ['Element 1', 'Element 2', 'Element 3'];

  print(settings['theme']); // dark
  print(items[0]); // Element 1
}

Thus, HashMap is used for quick key-based lookup, and ArrayList (List) for storing ordered data with iteration and index access.