Swift implementation of Linked List (Insert, Delete, Special insert).

LinkedList.swift

import UIKit

// Linked List (Insert, Delete, Special insert)
class Node {
    let value: Int
    var nextNode: Node?
    
    init(value:Int, nextNode: Node?) {
        self.value = value
        self.nextNode = nextNode
    }
}

class LinkedList {
    
    var headNode: Node?
    
    // 1. Insert
    func insert(value: Int) {
        //For first insertion
        if headNode == nil {
            headNode = Node(value: value, nextNode: nil)
            return
        }
        
        //For other insertion after the first one
        var currentNode = headNode
        while currentNode?.nextNode != nil {
            currentNode = currentNode?.nextNode
        }
        //When all insertion done, set the last node value and last nextNode to nil for the end of list
        currentNode?.nextNode = Node(value: value, nextNode: nil)
    }
    
    // 2. Delete
    func delete(value: Int) {
        // For first node
        if headNode?.value == value {
            headNode = headNode?.nextNode
        }
        
        //For others
        var previousNode: Node?
        var currentNode = headNode
        
        while currentNode != nil && currentNode?.value != value {
            previousNode = currentNode
            currentNode = currentNode?.nextNode
        }
        
        previousNode?.nextNode = currentNode?.nextNode
    }
    
    // 3. Special insert // Insert in order
    func insertInOrder(value: Int) {
        if headNode == nil || headNode?.value ?? Int.min >= value {
            let newMode = Node(value: value, nextNode: headNode)
            headNode = newMode
            return
        }
        var currentNode: Node? = headNode
        while currentNode?.nextNode != nil && currentNode?.nextNode?.value ?? Int.min < value {
            currentNode = currentNode?.nextNode
        }
        
        currentNode?.nextNode = Node(value: value, nextNode: currentNode?.nextNode)
    }
    
    func displayListItems() {
        print("Items in node:")
        var currentNode = headNode
        while currentNode != nil {
            print(currentNode?.value ?? "")
            currentNode = currentNode?.nextNode
        }
    }
    
    func setupNodes() { // Dummy node, 1->2->3->nil
        
        let three = Node(value: 3, nextNode: nil)
        let two = Node(value: 2, nextNode: three)
        headNode = Node(value: 1, nextNode: two)
    }
}

let linkedList = LinkedList()
//linkedList.setupNodes()
linkedList.insert(value: 1)
linkedList.insert(value: 2)
linkedList.insert(value: 4)
linkedList.insert(value: 5)

linkedList.insertInOrder(value: 3)
//linkedList.delete(value: 2)
linkedList.displayListItems()