Notes on List Data Structure Lecture

Introduction

• Importance of understanding list data structures in programming.
• Objective of the lecture: Create an application to practice working with lists.

What is a List?

• A list is a data structure used to store a collection of data (multiple items of the same type).
• Benefits of using lists:
  • Easier management of data.
  • Quick access to add, remove, and sort items.

Real-Life Examples

• Shopping List Example:
  • Write down items to buy, check them off after purchase.
• In programming, similar functionality can be mimicked:
  • Create a list programmatically.
  • Examples of functions like adding/removing items are simpler in programming.

List Characteristics

• Lists can contain multiple elements or be empty.
• Example of an empty list: a list of boys dated (count = 0).
• Purpose of lists: Organizing data efficiently.

Creating Lists in Programming

• Syntax:
  • List<Type> listName = new List<Type>(); for an empty list.
  • List<String> shoppingList = new List<String>() { "item1", "item2", ... }; for an initialized list.
• Example of creating a list:

  List<string> shoppingList = new List<string>() { "chocolate", "banana", "sugar", "milk", "cereal" };
  

Accessing List Elements

• Use a for each loop to iterate through and print items:

  foreach (string item in shoppingList) {
      Console.WriteLine(item);
  } 
  

Adding and Removing Items

• To add an item:
  • shoppingList.Add("itemName");
• To remove an item:
  • shoppingList.Remove("itemName");
• Demonstrated adding "lemon" and "apple" to the shopping list.

Sorting Lists

• To sort items alphabetically:
  • shoppingList.Sort();
• Sorting behavior described based on item types (strings, numbers).

Interactive Program Development

• Refactor the program to allow user input for adding/removing items.
• Example structure:
  • While the list is not empty, display the list, ask for input:

    while (shoppingList.Count != 0) { 
        // Display list and gather input 
    }
    

Improving User Experience

• Make user input more intuitive by printing prompts on the same line.
• Clear the console after each operation for clarity:

  Console.Clear();
  

Bidirectional Adding/Removing

• Program adjusted to check if the user input exists:
  • If exists: remove from list.
  • If not: add to list.
• Checking mechanism:

  if (shoppingList.Contains(userInput)) {
      shoppingList.Remove(userInput);
  } else {
      shoppingList.Add(userInput);
  }
  

Handling Case Sensitivity

• Convert user input to lowercase to avoid duplicates based on casing.

  shoppingList.Add(userInput.ToLower());
  shoppingList.Remove(userInput.ToLower());
  

Infinite Loop Structure

• Changing loop structure to run infinitely:

  while (true) {
      // Continuous operations 
  }
  

Conclusion

• Understanding how to effectively use lists in programs is essential.
• Encouraged to ask questions and provide feedback.
• Mention of an available practical programming course for deeper learning.