How to split an array in half in Swift?

You can make an extension so it can return an array of two arrays, working with Ints, Strings, etc:

extension Array {
    func split() -> [[Element]] {
        let ct = self.count
        let half = ct / 2
        let leftSplit = self[0 ..< half]
        let rightSplit = self[half ..< ct]
        return [Array(leftSplit), Array(rightSplit)]
    }
}

let deck = ["J", "Q", "K", "A"]
let nums = [0, 1, 2, 3, 4]

deck.split() // [["J", "Q"], ["K", "A"]]
nums.split() // [[0, 1], [2, 3, 4]]

But returning a named tuple is even better, because it enforces the fact that you expect exactly two arrays as a result:

extension Array {
    func split() -> (left: [Element], right: [Element]) {
        let ct = self.count
        let half = ct / 2
        let leftSplit = self[0 ..< half]
        let rightSplit = self[half ..< ct]
        return (left: Array(leftSplit), right: Array(rightSplit))
    }
}

let deck = ["J", "Q", "K", "A"]

let splitDeck = deck.split()
print(splitDeck.left) // ["J", "Q"]
print(splitDeck.right) // ["K", "A"]

Note: credits goes to Andrei and Qbyte for giving the first correct answer, I’m just adding info.