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# Dart – Sets

Sets in Dart is a special case in List where all the inputs are unique i.e it doesn’t contain any repeated input. It can also be interpreted as an unordered array with unique inputs. The set comes in play when we want to store unique values in a single variable without considering the order of the inputs. The sets are declared by the use of a set keyword.

There are two ways to do so:

var variable_name = <variable_type>{};

or,

Set <variable_type> variable_name = {};

Example 1: Declaring set in two different ways.

## Dart

 // Dart program to show the Sets concept void main() {   // Declaring set in First Way   var gfg1 = {'GeeksForGeeks'};       // Printing First Set   print("Output of first set: \$gfg1");       // Declaring set in Second Way   Set gfg2 = {'GeeksForGeeks'};        // Printing Second Set   print("Output of second set: \$gfg2"); }

Output:

Output of first set: {GeeksForGeeks}
Output of second set: {GeeksForGeeks}

Example 2: Declaring repeated value in a set and a list and then comparing it.

## Dart

 // Dart Program to declare repeated value // in a set and a list and then // comparing it   void main() {   // Declaring list with repeated value   var gfg = ['Geeks','For','Geeks'];       // Printing List   print("Output of the list is: \$gfg");       // Declaring set with repeated value   var gfg1 = {'Geeks','For','Geeks'};        // Printing Set   print("Output of the set is: \$gfg1"); }

Output:

Output of the list is: [Geeks, For, Geeks]
Output of the set is: {Geeks, For}

Note: You can see that repeated value was simply ignored in the case of the set.

Adding Element In Set: To add an element in the set we make use of “.add()” function or “.addAll()” function. But you must note that if you try to add a duplicate value using these functions then too they will get ignored in a set.

Some other functions involving Sets are as follows:

Example:

## Dart

 void main() {   // Declaring set with value   var gfg = {'Hello Geek'};       // Printing Set   print("Value in the set is: \$gfg");       // Adding an element in the set   gfg.add("GeeksForGeeks");       // Printing Set   print("Values in the set is: \$gfg");       // Adding multiple values to the set   var geeks_name = {"Geek1","Geek2","Geek3"};   gfg.addAll(geeks_name);       // Printing Set   print("Values in the set is: \$gfg");       // Getting element at Index 0   var geek = gfg.elementAt(0);       // Printing the element   print("Element at index 0 is: \$geek");       // Counting the length of the set   int l = gfg.length;       // Printing length   print("Length of the set is: \$l");       // Finding the element in the set   bool check = gfg.contains("GeeksForGeeks");       // Printing boolean value   print("The value of check is: \$check");       // Removing an element from the set   gfg.remove("Hello Geek");       // Printing Set   print("Values in the set is: \$gfg");       // Using forEach in set   print(" ");   print("Using forEach in set:");   gfg.forEach((element) {     if(element == "Geek1")     {       print("Found");     }     else     {       print("Not Found");     }   });       // Deleting elements from set   gfg.clear();       // Printing set   print("Values in the set is: \$gfg"); }

Output:

Value in the set is: {Hello Geek}
Values in the set is: {Hello Geek, GeeksForGeeks}
Values in the set is: {Hello Geek, GeeksForGeeks, Geek1, Geek2, Geek3}
Element at index 0 is: Hello Geek
Length of the set is: 5
The value of check is: true
Values in the set is: {GeeksForGeeks, Geek1, Geek2, Geek3}

Using forEach in set:
Found
Values in the set is: {}

Converting Set to List in Dart: Dart also provides us with the method to convert the set into the list. To do, so we make use of toList() method in Dart.

List<type> list_variable_name = set_variable_name.toList();

Note: It is useful in the way as the list we will get will contain unique values and no repeated values.

Example:

## Dart

 // Converting Set to List in Dart void main() {   // Declaring set with value   var gfg = {'Hello Geek',"GeeksForGeeks","Geek1","Geek2","Geek3"};        // Printing values in set   print("Values in set are:");   print(gfg);       print("");       // Converting Set to List   List gfg_list = gfg.toList();       // Printing values of list   print("Values in the list are:");   print(gfg_list); }

Output:

Values in set are:
{Hello Geek, GeeksForGeeks, Geek1, Geek2, Geek3}

Values in the list are:
[Hello Geek, GeeksForGeeks, Geek1, Geek2, Geek3]

Converting Set to Map in Dart: Dart also provides us with the method to convert the set into the map.

Example:

## Dart

 // Converting Set to Map in Dart void main() {   // Declaring set 1 with value   var gfg = {"GeeksForGeeks","Geek1","Geek2","Geek3"};       var geeksforgeeks = gfg.map((value) {     return 'mapped \$value';   });   print("Values in the map:");   print(geeksforgeeks);       }

Output:

Values in the map:
(mapped GeeksForGeeks, mapped Geek1, mapped Geek2, mapped Geek3)

Set Operations in Dart: There are three operations on set in Dart:

Example:

## Dart

 // Set Operations in Dart   void main() {   // Declaring set 1 with value   var gfg1 = {"GeeksForGeeks","Geek1","Geek2","Geek3"};       // Printing values in set   print("Values in set 1 are:");   print(gfg1);       print("");       // Declaring set 2 with value   var gfg2 = {"GeeksForGeeks","Geek3","Geek4","Geek5"};       // Printing values in set   print("Values in set 2 are:");   print(gfg2);       print("");           // Finding Union   print("Union of two sets is \${gfg1.union(gfg2)} \n");       // Finding Intersection   print("Intersection of two sets is \${gfg1.intersection(gfg2)} \n");       // Finding Difference   print("Difference of two sets is \${gfg2.difference(gfg1)} \n");       }

Output:

Values in set 1 are:
{GeeksForGeeks, Geek1, Geek2, Geek3}

Values in set 2 are:
{GeeksForGeeks, Geek3, Geek4, Geek5}

Union of two sets is {GeeksForGeeks, Geek1, Geek2, Geek3, Geek4, Geek5}

Intersection of two sets is {GeeksForGeeks, Geek3}

Difference of two sets is {Geek4, Geek5}

In the above code, we can also compare more than two sets as:

Example:

## Dart

 // Comparing more than 2 sets in Dart   void main() {   // Declaring set 1 with value   var gfg1 = {"GeeksForGeeks","Geek1","Geek2","Geek3"};       // Declaring set 2 with value   var gfg2 = {"GeeksForGeeks","Geek3","Geek4","Geek5"};       // Declaring set 3 with value   var gfg3 = {"GeeksForGeeks","Geek5","Geek6","Geek7"};       // Finding Union   print("Union of two sets is \${gfg1.union(gfg2).union(gfg3)}\n");       // Finding Intersection   print("Intersection of two sets is \${gfg1.intersection(gfg2).intersection(gfg3)}\n");       // Finding Difference   print("Difference of two sets is \${gfg2.difference(gfg1).difference(gfg3)}\n"); }

Output:

Union of two sets is {GeeksForGeeks, Geek1, Geek2, Geek3, Geek4, Geek5, Geek6, Geek7}

Intersection of two sets is {GeeksForGeeks}

Difference of two sets is {Geek4}

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