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],[2,4]]

但返回一个命名元组甚至更好,因为它强制执行这样一个事实：你期望正好两个数组：

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","A"]

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

注意：获得第一个正确答案的是Andrei和Qbyte,我只是添加信息.