public void AddLast(object data)
{
MyLinkedListNode node = new MyLinkedListNode(data);
if (count == 0)
{
first = node;
}
else
{
last.next = node; // this one I could not figure out
node.previous = last; // I figured this out
}
last = node; // I figured this out
count++;
}
public void AddFirst(object data)
{
// create a new node
MyLinkedListNode node = new MyLinkedListNode(data);
if (count == 0) // no other nodes exist yet!
{
first = node;
last = node;
}
else
{
node.next = first; // connects New Node to the CURRENT First Node
first.previous = node; // connects the CURRENT First Node to New Node
first = node; // make New Node the First Node
}
count++; // more effecient than +1
}
// help us manage all the nodes using Methods() e.g. Add, Remove, and SearchFor node
public MyLinkedListNode AddAfter(MyLinkedListNode node, object data)
{
MyLinkedListNode newnode = new MyLinkedListNode(data);
if (node == null)
{
throw new ArgumentNullException("null object!");
}
if (node == last)
{
AddLast(newnode); // AddLast increments the count for us!
return(newnode);
}
MyLinkedListNode temp = node.next;
node.next = newnode;
newnode.previous = node;
newnode.next = temp;
temp.previous = newnode;
count++; // always manage the count of nodes!!
return(newnode);
}
public void RemoveFirst()
{
if (count == 0)
{
throw new InvalidOperationException();
}
else if (count == 1)
{
first = last = null; // both First and Last are pointing to self to orphan it
}
else
{
// disconnect links between First and Next Nodes
first.next.previous = null;
// save a reference to the Next Node before cutting link to Next node
MyLinkedListNode second = first.next;
second.previous = null;
first.next = null;
// now delete the last link
first = second;
// object is now orphaned and GC will take care of it eventually
}
count--;
}
private int count; // tracks number of nodes in linked list
public MyLinkedList() // default CTOR to build an empty linked list
{
first = null;
last = null;
count = 0;
}
static void Main(string[] args)
{
try
{
// TESTS
// addfirst
// addlast
// copyto
Console.WriteLine("Creating linked list => 10 thru 70...");
MyLinkedList list1 = new MyLinkedList();
list1.AddFirst(10);
list1.AddFirst(20);
list1.AddFirst(30);
list1.AddFirst(40);
list1.AddFirst(50);
list1.AddFirst(60);
list1.AddFirst(70);
Console.WriteLine("Executing AddLast() => 80, 90, and 100...");
// test AddLast()
list1.AddLast(80);
list1.AddLast(90);
list1.AddLast(100);
Console.WriteLine("Creating an Array and copying Linked List into it...");
// make an array
object[] arr1 = new object[list1.Count];
// copy linked list back to an array
list1.CopyTo(arr1, 0);
// display the array
Console.WriteLine("Executing static void Display() method...");
Display(arr1);
// test RemoveFirst, copy it to a new array, then display array
list1.RemoveFirst();
object[] arr2 = new object[list1.Count];
list1.CopyTo(arr2, 0);
Console.WriteLine("\nExecuted RemoveFirst()...");
Display(arr2);
// test RemoveLast, copy it to a new array, then display array
list1.RemoveLast(); // TODO: Create RemoveLast() method in class MyLinkedList
object[] arr3 = new object[list1.Count];
list1.CopyTo(arr3, 0);
Console.WriteLine("\nExecuted RemoveLast()...");
Display(arr3);
// Test Find Data
Console.WriteLine("\nExecuting Find(50)... a findable value");
int value = 50;
MyLinkedListNode f1 = list1.Find(value);
if (f1 != null)
{
Console.WriteLine($"Found node {f1.data}!");
}
else
{
Console.WriteLine($"Unable to find node with data = {value}.");
}
Console.WriteLine("\nExecuting Find(10)... not a findable value");
value = 100;
MyLinkedListNode f2 = list1.Find(value);
if (f2 != null)
{
Console.WriteLine($"Found node {f2.data}!");
}
else
{
Console.WriteLine($"Unable to find node with data = {value}.");
}
Console.WriteLine("\nExecuting AddAfter(f4, 80)");
MyLinkedListNode f3 = new MyLinkedListNode(300);
// add data=800 after data=80
// 1) Find Node with data:80
// 2) Apply the AddAfter()
MyLinkedListNode f4 = list1.Find(80);
MyLinkedListNode addafter = list1.AddAfter(f4, 800); // f4=node to add after, 800=data for newnode
object[] arr4 = new object[list1.Count];
list1.CopyTo(arr4, 0);
Display(arr4);
// In-Class Exercise
Console.WriteLine("Press <Enter> to see In-Class Exercise results. . .");
Console.ReadLine();
Console.Clear();
MyLinkedList list2 = new MyLinkedList();
list2.AddLast("John");
list2.AddLast("Sandra");
list2.AddLast("Michelle");
list2.AddLast("Peter");
addafter = list2.Find("Sandra");
list2.AddAfter(addafter, "Robert");
addafter = list2.Find("Robert");
list2.AddAfter(addafter, "Karen");
object[] arr5 = new object[list2.Count];
list2.CopyTo(arr5, 0);
Display(arr5);
list2.RemoveFirst(); // should be John
list2.RemoveFirst(); // should be Sandra
object[] arr6 = new object[list2.Count];
list2.CopyTo(arr6, 0);
Display(arr6);
}
catch (Exception ex)
{
Console.WriteLine($"\n{ex.GetType().Name} : {ex.Message}\n{ex.StackTrace}");
}
// End of coding
Console.ReadLine();
}
public MyLinkedListNode(object data) // CTOR
{
this.data = data;
next = null; // we dont yet know what they will be set to
previous = null; // alternately could do next = previous = null (without shadowing!)
}