Swift: Remove duplicates from array

Swift: Remove Duplicates from Array

In Swift, arrays can contain duplicate elements, but often you need a collection with unique values. This example demonstrates simple and efficient ways to remove duplicates from an array using built-in Swift features like sets and the `filter` method.

Code

// Example array with duplicates
let numbers = [1, 2, 3, 2, 4, 1, 5]

// Method 1: Using a Set to remove duplicates (order not guaranteed)
let uniqueNumbersSet = Array(Set(numbers))
print(uniqueNumbersSet) // Output might be [2, 4, 5, 1, 3]

// Method 2: Using filter and a Set to preserve order
var seen = Set<Int>()
let uniqueNumbersOrdered = numbers.filter { number in
  if seen.contains(number) {
    return false
  } else {
    seen.insert(number)
    return true
  }
}
print(uniqueNumbersOrdered) // Output: [1, 2, 3, 4, 5]

Key Points

• Using a Set removes duplicates but does not preserve the original order of elements.
• Filtering with a Set allows you to remove duplicates while maintaining the array’s order.
• The `filter` method combined with a tracking Set is an efficient way to keep unique elements in sequence.
• Converting between arrays and sets is simple and leverages Swift’s standard library for common tasks.