diff --git a/course-source-files/section 12/LinkedListApp/LinkedList.h b/course-source-files/section 12/LinkedListApp/LinkedList.h
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+++ b/course-source-files/section 12/LinkedListApp/LinkedList.h	
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+#ifndef LINKED_LIST_H
+#define LINKED_LIST_H
+
+#include <iostream>
+#include "List.h"
+using namespace std;
+
+
+//-----------------Node--------------//
+class Node
+{
+	public:
+        Node(int data, Node* next)
+        {
+            this->data = data;
+            this->next = next;
+        }
+        int getData() const
+        {
+            return data;
+        }
+        void setData(int data)
+        {
+            this->data = data;
+        }
+        Node * getNext() const
+        {
+            return next;
+        }
+        void setNext(Node* next)
+        {
+            this->next = next;
+        }
+
+    private:
+            int data;
+            Node* next;
+};
+
+//-----------------Linked List class--------------//
+
+class LinkedList : public List
+{
+public:
+	LinkedList()
+	{
+		mNumElements = 0;
+		mHead = nullptr;  //empty list, no nodes
+	}//end ctor
+
+	//destructor - considered good programming to use virtual destructor
+	//in case you may delete an object of a derived class through a polymorphic pointer
+	virtual ~LinkedList()
+	{
+		makeEmpty();  
+	}
+
+	void add(int newEntry)
+	{
+		//ADT doesn't specify where to add it, so add at front!
+		Node* newNode = new Node(newEntry, mHead); //next = mHead
+		newNode->setNext(mHead);
+		mHead = newNode;
+
+		mNumElements++;
+	}//end add
+
+	//add to list at specified, 0-indexed position
+	//case 1:  add at beginning (position 0)
+	//case 2:  add somewhere that's not the beginning
+	void add(int newEntry, int position)
+	{
+		Node* newNode = new Node(newEntry, mHead);
+
+		//allow adding at the end, so @mNumElements itself is okay
+		if (position >= mNumElements + 1 || position < 0)
+		{
+			//could also use exceptions
+			cout << "Error:  Cannot add at specified position" << endl;
+			return;  //get out of here. 
+		}
+
+		if (position == 0)  //case 1
+		{
+			newNode->setNext(mHead);
+			mHead = newNode;
+		}
+		else  //case 2
+		{
+            // not beginning
+			Node* nodeBefore = mHead;
+			Node* nodeAfter;
+
+			for (int i = 0; i < position - 1; i++)
+			{
+				//find the nodeBefore the position we want
+				nodeBefore = nodeBefore->getNext();
+			}//end for
+
+			nodeAfter = nodeBefore->getNext();
+			//now splice our new node in between them
+			newNode->setNext(nodeAfter);
+			nodeBefore->setNext(newNode);  //instead of pointing to nodeAfter,
+										   //nodeBefore now points to the node we're adding
+
+		}
+
+		mNumElements++;
+	}//end add at position
+
+	//replace element at this position
+	void set(int newEntry, int position)
+	{
+		Node* walker = mHead;
+		int index = 0;
+
+		if (position >= mNumElements || position < 0)
+		{
+			//could also use exceptions
+			cout << "Error:  Cannot set at specified position" << endl;
+			return;  //get out of here. 
+		}
+
+		for (int i = 0; i < position; i++)
+		{
+			walker = walker->getNext();  //break out when i == position, which
+			                             //is where we want to add!  Yaaay!
+		}//end for 
+
+		//by now, we're at the position we want to add
+		walker->setData(newEntry);
+
+	}  //replace element at position
+
+	//leave for challenge at end
+	bool contains(int entry) const
+	{
+		bool result = false;
+
+		result = find(entry) != -1;  //is true if it does find it!
+
+		return result;
+	}  //does it exist?
+
+	int find(int entry) const
+	{
+		int foundIndex = -1;  //-1 means not found
+		int indexCounter = 0;
+		Node* walker = mHead;
+		while (walker != nullptr)
+		{
+			if (walker->getData() == entry)
+			{
+				foundIndex = indexCounter;
+				break; //get outta here
+			}
+
+			indexCounter++;
+		}
+
+		return foundIndex;
+	}  //return position of entry
+
+	int remove(int position)
+	{
+
+		if (position >= mNumElements || position < 0)
+		{
+			//could also use exceptions
+			cout << "Error:  Cannot remove at specified position" << endl;
+			return 0;  //get out of here. 
+		}
+
+		int dataToReturn = 0;
+
+		if (position == 0) //case:  first node
+		{
+			Node* temp = mHead;
+			dataToReturn = temp->getData();
+			mHead = mHead->getNext();
+			delete temp;  //remove it
+		}
+		else              //case:  any other node, positions 1, ...
+		{
+			//find element before, element itself, and element after
+			// and hold on to them, and bypass node at position
+			Node* nodeBefore = mHead;
+			Node* nodeToRemove;
+			Node* nodeAfter;
+
+			for (int i = 0; i < position - 1; i++)
+			{
+				nodeBefore = nodeBefore->getNext();
+			}//end for
+
+			//nodeBefore is at position - 1
+			nodeToRemove = nodeBefore->getNext();
+			dataToReturn = nodeToRemove->getData();
+
+			nodeAfter = nodeToRemove->getNext();
+
+			//bypass the node we're removing
+			nodeBefore->setNext(nodeAfter);
+
+			//delete the node
+			delete nodeToRemove;
+
+		}//end if-else
+
+		mNumElements--;  //one less item now
+
+		return dataToReturn;
+	}
+
+	//we actually have to delete the nodes
+	void makeEmpty()
+	{
+		//destroy all the nodes in the list
+		Node* temp;
+		while (mHead != nullptr)
+		{
+			temp = mHead;
+			mHead = mHead->getNext();
+			delete temp;
+		}//end while
+	}//end makeEmpty
+
+	int size() const
+	{
+		return mNumElements;
+	} //get length of list
+
+	bool isEmpty() const
+	{
+		return mNumElements == 0;
+	}//end isEmpty
+
+	void printList() const
+	{
+		Node* walker = mHead;
+
+		while (walker != nullptr)
+		{
+			cout << walker->getData() << endl;
+			walker = walker->getNext();
+		}
+	}//end printList
+  
+    private:
+        Node* mHead;  //the head of the list
+        int mNumElements;  //num elements
+};
+#endif
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