I use lists a lot
// Created by frank on 1/15/19.
<span style="font-size: 14pt;">// Copyright © 2019 frank. All rights reserved.
//
import Foundation
public class Node<T> {
var value: T
var next: Node<T>?
weak var previous: Node<T>?
init(value: T) {
self.value = value
}
}
public class LinkedList<T> {
fileprivate var head: Node<T>?
private var tail: Node<T>?
private var currentNode: Node<T>?
public var isEmpty: Bool {
return head == nil
}
public var first: Node<T>? {
return head
}
public var last: Node<T>? {
return tail
}
public var current: Node<T>? {
return currentNode
}
public func currentValue() -> T {
if currentNode == nil{
currentNode = head
}
let tValue = currentNode?.value
currentNode = currentNode?.next
return tValue!
}
public func currentIndexValue(index: Int) -> T {
var node = head
var count = 0
while node != nil {
if count == index{
break
}
node = node!.next
count = count + 1
}
return (node?.value)!
}
public func getNext() -> String {
var text = ""
text = "\(currentNode!.value)"
currentNode = currentNode?.next
if currentNode == nil{
currentNode = head
}
return text
}
public func append(value: T) {
let newNode = Node(value: value)
if let tailNode = tail {
newNode.previous = tailNode
tailNode.next = newNode
} else {
head = newNode
currentNode = head
}
tail = newNode
}
public func nodeAt(index: Int) -> Node<T>? {
if index >= 0 {
var node = head
var i = index
while node != nil {
if i == 0 { return node }
i -= 1
node = node!.next
}
}
return nil
}
public func removeAll() {
head = nil
tail = nil
}
public func getCount()->Int{
var node = head
var ecount = 0
while node != nil {
//text += "\(node!.value)"
node = node!.next
//if node != nil { text += ", " }
ecount = ecount + 1
}
return ecount
}
public func remove(node: Node<T>) -> T {
let prev = node.previous
let next = node.next
if let prev = prev {
prev.next = next
} else {
head = next
}
next?.previous = prev
if next == nil {
tail = prev
}
node.previous = nil
node.next = nil
return node.value
}
}
extension LinkedList: CustomStringConvertible {
public var description: String {
var text = "["
var node = head
while node != nil {
text += "\(node!.value)"
node = node!.next
if node != nil { text += ", " }
}
return text + "]"
}
}