Data Structures And Algorithms in Dart : Arrays

In Dart, an array is an ordered list of items. You can use an array to store a collection of items, such as a list of names or a list of numbers.

To create an array in Dart, you can use the List type and specify the type of elements that the array will hold within angle brackets (< and >). For example:

List<int> numbers = [1, 2, 3, 4, 5];

This creates an array of integers called numbers with the elements 1, 2, 3, 4, and 5.

You can also use the new keyword to create an array:

List<String> names = new List<String>();

Arrays have many useful methods for adding, removing, and manipulating elements.

Some of the most common methods include :

Here are some common methods that you can use with arrays in Dart:

We will be using the following lists to explain the core array methods in Dart :

List<int> numbers = [1, 2, 3, 4, 5];

List<dynamic> mixed = [1, '2', 3.0, true, [4, 5]];

• add(element): Adds an element to the end of the array.

// Add an element to the end of the array
numbers.add(6); // [1, 2, 3, 4, 5, 6]

• addAll(elements): Adds all the elements of an iterable to the end of the array.

// Add multiple elements to the end of the array
numbers.addAll([7, 8, 9]); // [1, 2, 3, 4, 5, 6, 7, 8, 9]

• clear(): Removes all elements from the array.

numbers.clear();

• remove(element): Removes the first occurrence of an element from the array.

// Remove the first occurrence of an element from the array
numbers.remove(3); // [1, 2, 4, 5, 6, 7, 8, 9]

• removeAt(index): Removes the element at a specific index from the array.

// Remove the element at a specific index from the array
numbers.removeAt(2); // [1, 2, 5, 6, 7, 8, 9]

• removeLast(): Removes the last element from the array.

// Remove the last element from the array
numbers.removeLast(); // [1, 2, 5, 6, 7, 8]

• removeRange(start, end): Removes a range of elements from the array.

// Remove a range of elements from the array
numbers.removeRange(1, 3); // [1, 8]

• insert(index, element): Inserts an element at a specific index in the array.

// Insert an element at a specific index in the array
numbers.insert(1, 2); // [1, 2, 8]

• insertAll(index, elements): Inserts all the elements of an iterable at a specific index in the array.

// Insert multiple elements at a specific index in the array
numbers.insertAll(1, [3, 4, 5]); // [1, 3, 4, 5, 2, 8]

• sort([compare]): Sorts the elements in the array according to the provided comparator function.

// Sort the elements in the array
numbers.sort(); // [1, 2, 3, 4, 5, 8]

• indexOf(element): Returns the index of the first occurrence of an element in the array, or -1 if the element is not found.

// Get the index of the first occurrence of an element in the array
int index = numbers.indexOf(4); // 3

• lastIndexOf(element): Returns the index of the last occurrence of an element in the array, or -1 if the element is not found.

// Get the index of the last occurrence of an element in the array
int lastIndex = numbers.lastIndexOf(4); // 3

• sublist(start, [end]): Returns a new list containing the elements in a range of the array.

// Get a new list containing the elements in a range of the array
List<int> sublist = numbers.sublist(1, 3); // [2, 3]

• asMap(): Returns a new map view of the array.

// Get a new map view of the array
Map<int, int> map = numbers.asMap(); // {0: 1, 1: 2, 2: 3, 3: 4, 4: 5, 5: 8}

• forEach(function): Calls the provided function on each element in the array.

// Call a function on each element in the array
numbers.forEach((element) {
  print(element);
});

• fold(initialValue, combine): Reduces the array to a single value by repeatedly calling the combine function on the elements of the array, starting with the initialValue.

// Use .fold() to add all the elements in the array
int sum = numbers.fold(0, (prev, element) => prev + element); // 15

• generate(generator, [count]): Creates a new array where the elements are generated by calling the generator function. If the count parameter is provided, it specifies the number of elements to generate.

// Use .generate() to create an array of 10 random numbers
Random random = new Random();
List<int> randomNumbers = List.generate(10, (_) => random.nextInt(100));

• any(test): Returns true if at least one element of the array satisfies the provided test function.

// Check if any element in the array is greater than 4
bool anyGreaterThanFour = numbers.any((element) => element > 4); // true

• contains(element): Returns true if the array contains the specified element.

/ Check if the array contains the number 3
bool containsThree = numbers.contains(3); // true

• elementAt(index): Returns the element at the specified index in the array.

// Get the element at index 2 in the array
int elementAtIndexTwo = numbers.elementAt(2); // 3

• every(test): Returns true if every element of the array satisfies the provided test function.

// Check if every element in the array is greater than 0
bool allGreaterThanZero = numbers.every((element) => element > 0); // true

• expand(function): Returns a new array where each element is replaced by the elements returned by the function.

// Expand the array by multiplying each element by 2
List<int> expanded = numbers.expand((element) => [element * 2]).toList(); // [2, 4, 6, 8, 10]

• fillRange(start, end, fillValue): Sets the elements in a range of the array to a specified value.

// Set the elements in the second half of the array to 0
numbers.fillRange(2, 5, 0); // [1, 2, 0, 0, 0]

• firstWhere(test, [orElse]): Returns the first element that satisfies the provided test function, or a default value if no such element is found.

// Get the first element that is greater than 2
int firstGreaterThanTwo = numbers.firstWhere((element) => element > 2, orElse: () => null); // 0

• cast(): Casts the elements in the array to a specified type.

// Cast the elements of the array to type int
List<int> castToInt = mixed.cast<int>().toList(); // [1, 3]

• followedBy(other): Returns a new array containing the elements of the current array followed by the elements of another iterable.

• join([separator]): Concatenates the elements in the array into a single string, with an optional separator string between each element.
  

// Concatenate the elements of the array into a single string
String joined = mixed.join(', '); // '1, 2, 3.0, true, [4, 5]'

• lastWhere(test, [orElse]): Returns the last element that satisfies the provided test function, or a default value if no such element is found.

// Get the last element that is a boolean
bool lastBool = mixed.lastWhere((element) => element is bool, orElse: () => null); // true

• map(function): Returns a new array where each element is the result of calling the function on the corresponding element of the original array.

// Multiply each element in the array by 2
List<int> multiplied = mixed.map((element) => element * 2).toList(); // [2, '22', 6.0, true, [4, 5]]

• reduce(combine): Reduces the array to a single value by repeatedly calling the combine function on the elements of the array.

// Reduce the array to a single value by adding the elements
int sum = mixed.reduce((prev, element) => prev + element); // 15.0

• singleWhere(test, [orElse]): Returns the only element that satisfies the provided test function, or a default value if no such element is found.

// Get the only element that is a string
String singleString = mixed.singleWhere((element) => element is String, orElse: () => null); // '2

• skip(count): Returns a new array that skips the first count elements of the original array.

// Skip the first two elements of the array
List<dynamic> skipped = mixed.skip(2).toList(); // [3.0, true, [4, 5]]

• skipWhile(test): Returns a new array that skips elements from the original array while they satisfy the provided test function.

// Skip elements of the array while they are not a boolean
List<dynamic> skippedWhile = mixed.skipWhile((element) => element is! bool).toList(); // [true, [4, 5]]

• take(count): Returns a new array that contains the first count elements of the original array.

// Take the first three elements of the array
List<dynamic> taken = mixed.take(3).toList(); // [1, '2', 3.0]

• takeWhile(test): Returns a new array that contains elements from the original array while they satisfy the provided test function.

// Take elements of the array while they are not a boolean
List<dynamic> takenWhile = mixed.takeWhile((element) => element is! bool).toList(); // [1, '2', 3.0]

• toList(): Returns a new list with the elements of the original array.

// Convert the array to a list
List<dynamic> toList = mixed.toList(); // [1, '2', 3.0, true, [4, 5]]

• toSet(): Returns a new set with the elements of the original array.

// Convert the array to a set
Set<dynamic> toSet = mixed.toSet(); // {1, '2', 3.0, true, [4, 5]}

• toString(): Returns a string representation of the array. where(test): Returns a new array containing only the elements of the original array that satisfy the provided test function.

// Convert the array to a string
String toString = mixed.toString(); // '[1, 2, 3.0, true, [4, 5]]'

• whereType(): Returns a new array containing only the elements of the original array that are of the specified type.

// Get only the elements of the array that are a boolean
List<dynamic> whereBool = mixed.where((element) => element is bool).toList(); // [true]

// Get only the elements of the array that are a double
List<dynamic> whereDouble = mixed.whereType<double>().toList(); // [3.0]