MiSwift Challenge #2 - Linked List

miswift-challenge-2.swift

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

import Foundation

class Node<T> {
    
    let value: T
    var next: Node<T>?
    
    init(value: T) {
        self.value = value
    }
}

class LinkedList<T>: Sequence, CustomStringConvertible, ExpressibleByArrayLiteral {
    
    private (set) var head: Node<T>?
    private (set) var tail: Node<T>?
    
    func append(_ value: T) {
        let node = Node(value: value)
        
        if let head = head {
            head.next = node
        }
        else {
           head = node
        }

        tail = node
    }
    
    // MARK: - ExpressibleByArrayLiteral
    
    required init(arrayLiteral elements: T...) {
        for element in elements {
            append(element)
        }
    }
    
    // MARK: - Sequence
    
    func makeIterator() -> AnyIterator<T> {
        var node = head
        return AnyIterator {
            defer { node = node?.next }
            return node?.value
        }
    }
    
    // MARK: CustomStringConvertible
    
    var description: String {
        return map { $0 }.description
    }
}

let linkedList = LinkedList<Int>() // []
linkedList.append(1) // [1]
linkedList.append(2) // [1, 2]

let emojis: LinkedList = ["🌊", "🚘"]
emojis.head?.value // "🌊"
emojis.tail?.value // "🚘"