# Quick guide to Swift array partition

## Introduction

The `partition(by:)` method in Swift allows you to divide an array into two smaller groups, based on a predicate. This can be useful for tasks such as sorting, filtering, and grouping.

In this blog post, we will provide a quick guide to using Swift array partition. We will cover the basics of how to use the method, as well as some common use cases.

## How to use Swift array partition

The `partition(by:)` method takes a predicate as its only argument. The predicate is a function that takes an element of the array as its argument and returns a Boolean value. The `partition(by:)` method will divide the array into two groups: the elements for which the predicate returns `true` and the elements for which the predicate returns `false`.

The following code shows how to use the `partition(by:)` method to divide an array of numbers into two groups: even numbers and odd numbers:

```let numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

// Predicate to check if a number is even
let isEvenPredicate: (Int) -> Bool = { \$0 % 2 == 0 }

// Divide the array into even and odd numbers
let (evenNumbers, oddNumbers) = numbers.partition(by: isEvenPredicate)

// Print the even and odd numbers
print(evenNumbers) // [2, 4, 6, 8, 10]
print(oddNumbers) // [1, 3, 5, 7, 9]
```

## Common use cases for Swift array partition

The `partition(by:)` method can be used for a variety of tasks, including:

• Sorting: You can use the `partition(by:)` method to sort an array in ascending or descending order. To do this, you would use a predicate that checks if an element is greater than or less than another element.
• Filtering: You can use the `partition(by:)` method to filter an array, removing all of the elements that do not match a given predicate.
• Grouping: You can use the `partition(by:)` method to group an array into two or more smaller groups, based on different criteria.

Here are some specific examples of how to use the `partition(by:)` method for sorting, filtering, and grouping:

```// Sort an array of numbers in ascending order
let numbers = [10, 3, 2, 5, 4, 1, 6, 7, 8, 9]
let sortedNumbers = numbers.partition(by: { \$0 < \$1 })

// Filter an array of strings to remove all of the empty strings
let strings = ["a", "", "b", "", "c"]
let filteredStrings = strings.partition(by: { \$0.isEmpty })

// Group an array of people by their age
let people = [Person(age: 20), Person(age: 30), Person(age: 40)]

let (under30, over30) = people.partition(by: { \$0.age < 30 })
```

## Conclusion

The `partition(by:)` method is a powerful tool that can be used to divide an array into two or more smaller groups, based on different criteria. It is a versatile method that can be used for a variety of tasks, such as sorting, filtering, and grouping.