swift Array dropFirst() Function

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The dropFirst() function of an array is used to remove the specified number of elements from the beginning of the given array. Using this function we can remove as many as element we want from the beginning of the array. If the number of elements we want to remove is greater than the size of the array, then this function will return an empty array. The complexity of this function is O(1).

For example, we have an array = [10, 13, 18, 19]. Now using the dropFirst(2) function we removed the first 2 elements from the array. Hence the resultant array is [18, 19].

Syntax

Following is the syntax of the dropFirst() function −

func dropFirst(_x: Int) -> Self.SubSequence

Parameters

This function takes only one parameter which is x. Here x represents the number of elements we want to remove from the beginning of the given array. If this function does not contain any parameter, then it will remove the first element from the given array.

Return value

This function returns an array after removing the initial elements.

Now we will discuss how to use the dropFirst() function with the help of the following examples:

Example 1

Swift program to demonstrate the dropFirst() function. Here we will see how the dropFirst() function works with different data types.

import Foundation

// Array of string type
var arrayOne = ["mango", "apple", "orange", "graps"]
print("Original array:", arrayOne)

// Removing first two elements using dropFirst() function
print("Modified array:\(arrayOne.dropFirst(2))")

// Array of integer type
var arrayTwo = [8, 3, 1, 9, 3]
print("\nOriginal array:", arrayTwo)

// Removing first three elements using dropFirst() function
print("Modified array:\(arrayTwo.dropFirst(3))")

// Array of double type
var arrayThree = [1.2, 25.3, 60.3, 7.2, 83.4, 10.33]
print("\nOriginal array:", arrayThree)

// Removing first element using dropFirst() function
print("Modified array:\(arrayThree.dropFirst(1))")

Output

Original array: ["mango", "apple", "orange", "graps"]
Modified array:["orange", "graps"]

Original array: [8, 3, 1, 9, 3]
Modified array:[9, 3]

Original array: [1.2, 25.3, 60.3, 7.2, 83.4, 10.33]
Modified array:[25.3, 60.3, 7.2, 83.4, 10.33]

Example 2

Swift program to demonstrate the different behaviour of the dropFirst() function. Here we will see how the dropFirst() function reacts when we do not pass any parameter to it and when we pass the number of elements greater than the size of the array.

import Foundation

// Array of integer type
var array1 = [2, 4, 5, 7]
print("Original Array:", array1)

// Calling dropFrist() function without parameter
print("Modified array:", array1.dropFirst())

// Array of integer type
var array2 = [30, 20, 70, 60, 10, 80]
print("\nOriginal Array:", array2)

// Calling dropFrist() function with a parameter greater than the size of the array
print("Modified array:", array2.dropFirst(10))

Output

Original Array: [2, 4, 5, 7]
Modified array: [4, 5, 7]

Original Array: [30, 20, 70, 60, 10, 80]
Modified array: []

Example 3

Swift program to remove the first two rows from the given matrix using the dropFirst() function.

import Foundation

// Defining a matrix
var matrix = [
    [2, 5, 6, 7],
    [8, 3, 2, 1],
    [9, 2, 3, 1],
    [1, 1, 2, 2]
]

// Printing original matrix
print("Original Matrix:")
for x in matrix{
    print(x)
}

// Removing the first two rows from the matrix
matrix = Array(matrix.dropFirst(2))

// Printing the modified matrix
print("\nModified Matrix:")
for y in matrix {
    print(y)
}

Output

Original Matrix:
[2, 5, 6, 7]
[8, 3, 2, 1]
[9, 2, 3, 1]
[1, 1, 2, 2]

Modified Matrix:
[9, 2, 3, 1]
[1, 1, 2, 2]