Adding and Removing from Sets

Part of the Logic & Flow section of Coddy's Dart journey — lesson 19 of 65.

Once you have a Set, you'll often need to modify its contents by adding new elements or removing existing ones. The add() and remove() methods provide straightforward ways to manage your set's elements.

The add() method attempts to insert a new element into the set. However, since sets only store unique values, if you try to add an element that already exists, the method simply does nothing - no error occurs, and the set remains unchanged.

Set<String> usernames = {'alice', 'bob', 'charlie'};

usernames.add('diana');     // Adds 'diana' successfully
usernames.add('alice');     // Does nothing - 'alice' already exists

print(usernames);  // {alice, bob, charlie, diana}

The remove() method works by taking the value you want to delete and removing it from the set. If the element doesn't exist in the set, the method simply does nothing, making it safe to use without checking first.

usernames.remove('bob');        // Removes 'bob'
usernames.remove('unknown');    // Does nothing - element not found

print(usernames);  // {alice, charlie, diana}

Challenge

Easy

Create a program that manages a team collaboration system by adding new team members and removing inactive ones from a project team. Your program should:

Read a string input representing the project name
Read multiple string inputs representing initial team members (the input will end when you receive "initial_done")
Read multiple string inputs representing new members to add (the input will end when you receive "add_done")
Read multiple string inputs representing members to remove (the input will end when you receive "remove_done")
Create a Set with the initial team members
Use the add() method to add each new member to the team
Use the remove() method to remove each specified member from the team
Print the team management results in the exact format shown below

For example, if the project name is "Mobile App Development", the initial members are "Alice", "Bob", "Charlie", the new members to add are "Diana", "Alice", "Eve", and the members to remove are "Bob", "Frank", your program should output:

Project: Mobile App Development
Initial team: {Alice, Bob, Charlie}
Adding new members: [Diana, Alice, Eve]
After adding members: {Alice, Bob, Charlie, Diana, Eve}
Removing members: [Bob, Frank]
Final team: {Alice, Charlie, Diana, Eve}
Team size: 4
Status: Team updated successfully

If the project name is "Website Redesign", the initial members are "John", "Sarah", the new members to add are "Mike", "John", and the members to remove are "Sarah", "Unknown", your program should output:

Project: Website Redesign
Initial team: {John, Sarah}
Adding new members: [Mike, John]
After adding members: {John, Sarah, Mike}
Removing members: [Sarah, Unknown]
Final team: {John, Mike}
Team size: 2
Status: Team updated successfully

If the project name is "Data Analysis", the initial members are "Emma", the new members to add are "Tom", "Lisa", and the members to remove are "Emma", your program should output:

Project: Data Analysis
Initial team: {Emma}
Adding new members: [Tom, Lisa]
After adding members: {Emma, Tom, Lisa}
Removing members: [Emma]
Final team: {Tom, Lisa}
Team size: 2
Status: Team updated successfully

Your program must demonstrate that the add() method does nothing when trying to add a member who already exists, and the remove() method does nothing when trying to remove a member who doesn't exist. Store the input lists to show what operations were attempted, then show the Set contents after each operation to demonstrate the unique nature of Sets.

Cheat sheet

Use add() to insert elements into a Set. If the element already exists, nothing happens:

Set<String> usernames = {'alice', 'bob', 'charlie'};

usernames.add('diana');     // Adds 'diana' successfully
usernames.add('alice');     // Does nothing - 'alice' already exists

print(usernames);  // {alice, bob, charlie, diana}

Use remove() to delete elements from a Set. If the element doesn't exist, nothing happens:

usernames.remove('bob');        // Removes 'bob'
usernames.remove('unknown');    // Does nothing - element not found

print(usernames);  // {alice, charlie, diana}

Try it yourself

import 'dart:io';

void main() {
  // Read project name
  String? projectName = stdin.readLineSync();
  
  // Read initial team members
  List<String> initialMembers = [];
  String? member;
  while ((member = stdin.readLineSync()) != "initial_done") {
    initialMembers.add(member!);
  }
  
  // Read new members to add
  List<String> membersToAdd = [];
  while ((member = stdin.readLineSync()) != "add_done") {
    membersToAdd.add(member!);
  }
  
  // Read members to remove
  List<String> membersToRemove = [];
  while ((member = stdin.readLineSync()) != "remove_done") {
    membersToRemove.add(member!);
  }
  
  // TODO: Write your code below
  // Create a Set with initial team members
  // Add new members using add() method
  // Remove members using remove() method
  
  // Print the results in the required format
  print("Project: $projectName");
  // Add remaining print statements here
}