Swift Array - shuffle Function

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The shuffle() function of an array is used to shuffle the elements present in the given array. It shuffles elements randomly so whenever you run the code you will get different output. This function works only for mutating collections such as arrays, it does not work with non-mutating collections. Mutating collections are those collections that can be modified whereas non-mutating collections are those collections that cannot be modified, if we try to modify them we will get an error.

For example, we have an array = [34, 10, 38, 9, 19]. Now using the shuffle() function we shuffle the elements of the given array. Hence the resultant array is [9, 38, 19, 34, 10].

We can use the shuffle() function in two different types −

• shuffle() function
• shuffle(using:) function

Swift Array shuffle() Function

The shuffle() function is used to shuffle the elements of the given array randomly. It does not change the elements instead it only modifies their position. The complexity of this function is O(n), where n is the size of the given array.

Syntax

Following is the syntax of the shuffle() function −

func shuffle()

Parameters

This function does not take any parameter.

Return Value

This function returns an array with shuffled elements.

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

Example 1

Swift program to shuffle the elements of the given array using the shuffle() function.

import Foundation

// Array of integer type
var arr1 = [4, 5, 6, 7, 88, 89]
print("Original Array:", arr1)

// Shuffling the array elements
arr1.shuffle()

// Display the result
print("Shuffled Array:", arr1)

// Array of string type
var arr2 = ["Swift", "Java", "C++"]
print("\nOriginal Array:", arr2)

// Shuffling the array elements
arr2.shuffle()

// Display the result
print("Shuffled Array:", arr2)

// Array of mixed type
var arr3: [Any] = [3.2, "Swift", 4, "Hello", false]
print("\nOriginal Array:", arr3)

// Shuffling the array elements
arr3.shuffle()

// Display the result
print("Shuffled Array:", arr3)

Output

Original Array: [4, 5, 6, 7, 88, 89]
Shuffled Array: [5, 6, 89, 7, 4, 88]

Original Array: ["Swift", "Java", "C++"]
Shuffled Array: ["Swift", "C++", "Java"]

Original Array: [3.2, "Swift", 4, "Hello", false]
Shuffled Array: ["Swift", false, 4, "Hello", 3.2]

Example 2

Swift program to shuffle the elements of a 2-D array using the shuffle() function. Here we shuffle each row of the given 2-D array.

import Foundation

// Defining 2-D array
var twoDArray = [
   [3, 5, 7, 8, 9],
   [3, 4, 6, 8, 9],
   [1, 3, 5, 75, 4],
]
// Print the original
print("Original 2D Array:")
for row in twoDArray {
   print(row)
}

// Shuffling 2-D array
twoDArray.shuffle()

// Print Shuffled array
print("\nShuffled 2D Array:")
for row in twoDArray {
   print(row)
}

Output

Original 2D Array:
[3, 5, 7, 8, 9]
[3, 4, 6, 8, 9]
[1, 3, 5, 75, 4]

Shuffled 2D Array:
[3, 5, 7, 8, 9]
[3, 4, 6, 8, 9]
[1, 3, 5, 75, 4]

Swift Array shuffle(using: ) Function

The shuffle(using:) function is used to shuffle the elements of the given array according to the given randomness generator. You can use a predefined random number generator or a custom random number generator. The complexity of this function is O(n), where n represents the length of the array.

Syntax

Following is the syntax of the shuffle(using:) function −

func shuffle<T>(using generator: inout T) where T : RandomNumberGenerator

Parameters

This function takes only one parameter which is a generator. The generator represents the random number generator that is used to shuffle the array.

Return Value

This function returns an array with shuffled elements.

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

Example 1

Swift program to shuffle the elements of the given array using shuffle(using:) function.

import Foundation

// Defining an array of integer type
var inputArr: [Int] = [10, 23, 11, 19, 20]

print("Original Array:", inputArr)

// Create a custom random number generator
var randomGenerator = SystemRandomNumberGenerator()

// Shuffle the array with a custom random generator
inputArr.shuffle(using: &randomGenerator)

print("Shuffled Array: \(inputArr)")

Output

Original Array: [10, 23, 11, 19, 20]
Shuffled Array: [19, 20, 10, 11, 23]

Example 2

Swift program to shuffle the array using a custom random generator and then find their sum.

import Foundation

// Defining an array of integer type
var inputArr: [Int] = [10, 23, 11, 19, 20]

print("Original Array:", inputArr)

// Create a custom random number generator
var randomGenerator = SystemRandomNumberGenerator()

// Shuffle the array with a custom random generator
inputArr.shuffle(using: &randomGenerator)
print("Shuffled Array: \(inputArr)")

// Calculating the sum of the array elements using reduce() function
let sum = inputArr.reduce(0, +)

print("Sum: \(sum)")

Output

Original Array: [10, 23, 11, 19, 20]
Shuffled Array: [20, 11, 23, 10, 19]
Sum: 83