An extension for Swift Array that returns the difference between two arrays

Array+Diff.swift

//: Playground - noun: a place where people can play

extension Array where Element: Comparable {
    /**
     Compares array with passed array and returns the differences. Warning: Must be a set of data (no duplicate values)
     - Parameter with: The new array to compare to the existing array
     - Returns: A tuple with an array of added items and an array of removed items.
     */
    func diff(with array: Array) -> (added: Array, removed: Array) {
        let originalArray = self.sorted()
        let newArray = array.sorted()
        var addedItems: [Element] = []
        var removedItems: [Element] = []
        var originalIndex = 0
        var newIndex = 0
        
        while originalIndex < originalArray.count && newIndex < newArray.count {
            if originalArray[originalIndex] < newArray[newIndex] {
                removedItems.append(originalArray[originalIndex])
                originalIndex += 1
            } else if originalArray[originalIndex] > newArray[newIndex] {
                addedItems.append(newArray[newIndex])
                newIndex += 1
            } else {
                newIndex += 1
                originalIndex += 1
            }
        }
        
        if newIndex < newArray.count {
            addedItems.append(contentsOf: newArray[newIndex..<newArray.count])
        }
        if originalIndex < originalArray.count {
            removedItems.append(contentsOf: originalArray[originalIndex..<originalArray.count])
        }
        
        return (added: addedItems, removed: removedItems)
    }
}


let original = [7, 3, 4, 6]
let new = [2, 4, 9, 10, 7]

let result = original.diff(with: new)

print(result.added) //prints [2, 9, 10]
print(result.removed) //prints [3, 6]

Or just use set:

let original = Set([7, 3, 4, 6, 7])
let new = Set([2, 4, 9, 10, 7])

let removed = original.subtracting(new)
let added = new.subtracting(original)

print(removed) //prints [6, 3]
print(added) //prints [10, 2, 9]