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Sets

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In Dart, a Set is an unordered collection of unique items. Sets are particularly useful when you need to ensure that no duplicate elements are present in your collection. In this section, we will cover the following topics:

  1. Introduction to Sets
  2. Creating Sets
  3. Adding and Removing Elements
  4. Set Operations
  5. Iterating Over Sets
  6. Practical Examples
  7. Exercises

  1. Introduction to Sets

A Set in Dart is a collection of unique elements. Unlike Lists, Sets do not maintain the order of elements. Sets are useful when you need to store a collection of items and ensure that each item is unique.

  1. Creating Sets

You can create a Set in Dart using the Set class. Here are a few ways to create a Set:

Using the Set Constructor

void main() {
  Set<int> numbers = Set();
  print(numbers); // Output: {}
}

Using Set Literals

void main() {
  Set<String> fruits = {'apple', 'banana', 'orange'};
  print(fruits); // Output: {apple, banana, orange}
}

Using the Set.from Constructor

void main() {
  List<int> list = [1, 2, 3, 4, 4, 5];
  Set<int> uniqueNumbers = Set.from(list);
  print(uniqueNumbers); // Output: {1, 2, 3, 4, 5}
}

  1. Adding and Removing Elements

You can add and remove elements from a Set using the add, addAll, remove, and removeAll methods.

Adding Elements

void main() {
  Set<String> fruits = {'apple', 'banana'};
  fruits.add('orange');
  print(fruits); // Output: {apple, banana, orange}
}

Adding Multiple Elements

void main() {
  Set<String> fruits = {'apple', 'banana'};
  fruits.addAll({'orange', 'grape'});
  print(fruits); // Output: {apple, banana, orange, grape}
}

Removing Elements

void main() {
  Set<String> fruits = {'apple', 'banana', 'orange'};
  fruits.remove('banana');
  print(fruits); // Output: {apple, orange}
}

Removing Multiple Elements

void main() {
  Set<String> fruits = {'apple', 'banana', 'orange', 'grape'};
  fruits.removeAll({'banana', 'grape'});
  print(fruits); // Output: {apple, orange}
}

  1. Set Operations

Dart provides several methods to perform operations on Sets, such as union, intersection, and difference.

Union

The union method returns a new Set containing all elements from both Sets.

void main() {
  Set<int> setA = {1, 2, 3};
  Set<int> setB = {3, 4, 5};
  Set<int> unionSet = setA.union(setB);
  print(unionSet); // Output: {1, 2, 3, 4, 5}
}

Intersection

The intersection method returns a new Set containing only the elements that are present in both Sets.

void main() {
  Set<int> setA = {1, 2, 3};
  Set<int> setB = {3, 4, 5};
  Set<int> intersectionSet = setA.intersection(setB);
  print(intersectionSet); // Output: {3}
}

Difference

The difference method returns a new Set containing the elements that are present in the first Set but not in the second Set.

void main() {
  Set<int> setA = {1, 2, 3};
  Set<int> setB = {3, 4, 5};
  Set<int> differenceSet = setA.difference(setB);
  print(differenceSet); // Output: {1, 2}
}

  1. Iterating Over Sets

You can iterate over the elements of a Set using a for loop or the forEach method.

Using a for Loop

void main() {
  Set<String> fruits = {'apple', 'banana', 'orange'};
  for (String fruit in fruits) {
    print(fruit);
  }
}

Using the forEach Method

void main() {
  Set<String> fruits = {'apple', 'banana', 'orange'};
  fruits.forEach((fruit) => print(fruit));
}

  1. Practical Examples

Example 1: Removing Duplicates from a List

void main() {
  List<int> numbers = [1, 2, 2, 3, 4, 4, 5];
  Set<int> uniqueNumbers = Set.from(numbers);
  print(uniqueNumbers); // Output: {1, 2, 3, 4, 5}
}

Example 2: Finding Common Elements Between Two Lists

void main() {
  List<int> listA = [1, 2, 3, 4];
  List<int> listB = [3, 4, 5, 6];
  Set<int> setA = Set.from(listA);
  Set<int> setB = Set.from(listB);
  Set<int> commonElements = setA.intersection(setB);
  print(commonElements); // Output: {3, 4}
}

  1. Exercises

Exercise 1: Create a Set of Integers

Create a Set of integers and add the numbers 1 to 5 to it. Then, print the Set.

void main() {
  // Your code here
}

Solution:

void main() {
  Set<int> numbers = {1, 2, 3, 4, 5};
  print(numbers); // Output: {1, 2, 3, 4, 5}
}

Exercise 2: Perform Set Operations

Given two Sets of integers, perform union, intersection, and difference operations and print the results.

void main() {
  Set<int> setA = {1, 2, 3};
  Set<int> setB = {3, 4, 5};
  
  // Your code here
}

Solution:

void main() {
  Set<int> setA = {1, 2, 3};
  Set<int> setB = {3, 4, 5};
  
  Set<int> unionSet = setA.union(setB);
  Set<int> intersectionSet = setA.intersection(setB);
  Set<int> differenceSet = setA.difference(setB);
  
  print('Union: $unionSet'); // Output: Union: {1, 2, 3, 4, 5}
  print('Intersection: $intersectionSet'); // Output: Intersection: {3}
  print('Difference: $differenceSet'); // Output: Difference: {1, 2}
}

Exercise 3: Remove Duplicates from a List

Given a List of integers with duplicate values, create a Set to remove the duplicates and print the unique values.

void main() {
  List<int> numbers = [1, 2, 2, 3, 4, 4, 5];
  
  // Your code here
}

Solution:

void main() {
  List<int> numbers = [1, 2, 2, 3, 4, 4, 5];
  Set<int> uniqueNumbers = Set.from(numbers);
  print(uniqueNumbers); // Output: {1, 2, 3, 4, 5}
}

Conclusion

In this section, we have learned about Sets in Dart, including how to create them, add and remove elements, perform set operations, and iterate over them. We also covered practical examples and exercises to reinforce the concepts. Understanding Sets is crucial for managing collections of unique items efficiently in your Dart programs. In the next section, we will explore Maps, another essential collection type in Dart.

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