Linked Lists
Chapter 3
1
Objectives
You will be able to:
 Describe an abstract data type for lists.
 Understand and use an implementation of
a List ADT.
2
Linked Lists


An alternative to arrays for storing an
ordered collection of data items of the
same type.
Normally, but not always, nodes are
dynamically allocated and deleted.


List can grow indefinitely.
“Linked” is an implementation issue.

The ADT is simply a “List”.
3
List Operations
Typical operations for a List ADT:
 Create list
 Insert item at head
 Insert item at tail
 Insert item at specified position
 Insert item in order
 Retrieve item at specified position
 Retrieve item with specified value or key
 Delete item
 Traverse
 Determine if list is empty
 Determine number of items in the list
 Destroy list

Many more
4
Linked Lists vs. Arrays

Advantages of lists



Efficient insertion and deletion at any
position.
No specific limit on size.
Disadvantages of lists

Lack of direct access to all nodes
5
List as an ADT

Use copy semantics.




Don’t give clients access to internals.
Insertion adds a copy of client's data to
the list.
Retrieval gives client a copy of the data.
All data is stored internally in the list.


No pointers to data outside
The list encapsulates the data.
6
Singly Linked Lists


Nodes consist of data + pointer.
List object has pointers to first node and
last node.



Null if list is empty
Each node has a pointer to the next node.
Last node has null pointer.
7
Singly Linked List Example

Code in Figure 3.2 on page 79 and
following


A singly linked list of integers.
Source files available from author’s web site:

http://www.mathcs.duq.edu/drozdek/DSinCpp/



intSLLst.h
intSLLst.cpp
To look at the example, create an empty
Visual Studio C++ project and download the
files into the project directory.

Or copy the files into an empty directory on Circe.
8
Creating a Project
9
Creating a Project
10
Creating a Project
11
Creating a Project
12
Creating a Project
13
Project Directory
14
Project Directory
Download here.
15
After Download
The source files intSLLst.h and intSLLst.cpp are in the project directory,
but are not yet in the project.
We have to add them to the project.
16
Add Files to Project
17
Add Files to Project
18
Source Files in the Project
19
Still can’t compile

We don’t have a program yet.


Just a class definition.
Need a “main” in order to compile and
run.
20
Adding a “main”
21
Adding a “main”
22
Project with main.cpp
23
Start with a stub
24
Compile and Run
25
Compile Error
Evidently the author used an older compiler.
26
Fixing the Errors
27
Ready to Run
Click here to run.
28
Program Running
We have a working program!
Now we need to make it do something.
Start by looking at the class definition.
29
The Node Class
//************************ intSLLst.h ***************
//
singly-linked list class to store integers
#ifndef INT_LINKED_LIST
#define INT_LINKED_LIST
class IntSLLNode
{
public:
int info;
class IntSLLNode *next;
IntSLLNode(int el, IntSLLNode *ptr = 0)
{
info = el;
next = ptr;
}
};
30
The List Class
class IntSLList
{
public:
IntSLList()
{
head = tail = 0;
}
~IntSLList();
int isEmpty()
{
return head == 0;
}
void addToHead(int);
void addToTail(int);
int deleteFromHead(); // delete the head and return its info;
int deleteFromTail(); // delete the tail and return its info;
void deleteNode(int);
bool isInList(int) const;
void printAll() const;
private:
IntSLLNode *head, *tail;
};
31
main.cpp
#include <iostream>
#include "intSLLst.h"
using namespace std;
int main()
{
IntSLList myList;
cout << "Testing addToHead();\n";
cout << "Calling addtoHead for 3 2 1 0\n";
myList.addToHead(3);
myList.addToHead(2);
myList.addToHead(1);
myList.addToHead(0);
cout << "Initial List:\n";
myList.printAll();
cin.get();
}
// Hold window open.
32
Program Running
33
Test the Delete Method
cout << "\nTesting deleteFromHead\n";
while (!myList.isEmpty())
{
cout << "Deleting head node\n";
myList.deleteFromHead();
cout << "Current List:\n";
myList.printAll();
}
cin.get(); // Hold window open.
}
34
Program Running
35
Assignment
Before next class



Read Chapter 3, through section 3.1.3.
Download and read the author’s singly linked list
class files.
Do the example from today’s class for yourself
if you didn’t do it in class.

Read the .cpp file.


Understand every line!
Expect a quiz on this code next week.
Project 1
36