Here are my slides for my preparation class for possible Master students in Electrical Engineering and Computer Science (Specialization in Computer Science)... for the entrance examination here at Cinvestav GDL.

1. Data Structures
Iterators and Chain Linear List
Andres Mendez-Vazquez
May 6, 2015
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2. Images/cinvestav-
Outline
1 Iterators
Interface
Separate and Inner Class Iterator
2 Introduction
Linked Representation
Memory Layout
3 Operations
IsEmpty()
size()
Get(Index)
Remove
Add
4 Can we simplify the code?
5 Other data structures based in the Linked List
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3. Images/cinvestav-
Iterator Method
Scenario
We often want to access every item in a data structure or collection in
turn...
Example with the array representation
1 int listSize = SomeList.size();
2 for (int i = 0; i < listSize; i++)
3 System.out.println(SomeList.get(i));
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4. Images/cinvestav-
Iterator Method
Scenario
We often want to access every item in a data structure or collection in
turn...
Example with the array representation
1 int listSize = SomeList.size();
2 for (int i = 0; i < listSize; i++)
3 System.out.println(SomeList.get(i));
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Motivation
Question
What if we have a get that is really complex?
For example the get in a Chain List
We will see that it has complexity O(n)!!!
Previous Code
What a waste of time!!! O n2 !!!!
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6. Images/cinvestav-
Motivation
Question
What if we have a get that is really complex?
For example the get in a Chain List
We will see that it has complexity O(n)!!!
Previous Code
What a waste of time!!! O n2 !!!!
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7. Images/cinvestav-
Motivation
Question
What if we have a get that is really complex?
For example the get in a Chain List
We will see that it has complexity O(n)!!!
Previous Code
What a waste of time!!! O n2 !!!!
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8. Images/cinvestav-
Then
Something Notable
Iteration is such a common operation that we could include it as part of
the ADT list.
However
We do not want to add another operation to the ADT each time we think
of another way to use an iteration.
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9. Images/cinvestav-
Then
Something Notable
Iteration is such a common operation that we could include it as part of
the ADT list.
However
We do not want to add another operation to the ADT each time we think
of another way to use an iteration.
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10. Images/cinvestav-
Outline
1 Iterators
Interface
Separate and Inner Class Iterator
2 Introduction
Linked Representation
Memory Layout
3 Operations
IsEmpty()
size()
Get(Index)
Remove
Add
4 Can we simplify the code?
5 Other data structures based in the Linked List
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11. Images/cinvestav-
In Java at java.util we have the interface Iterator
Interface
package java . u t i l ;
p u b l i c i n t e r f a c e I t e r a t o r <Item> {
p u b l i c boolean hasNext ( ) ;
p u b l i c Item next ( ) ;
// Optional method
p u b l i c void remove ( ) ;
} // end I t e r a t o r
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Explanation
public boolean hasNext()
It detects whether this iterator has completed its traversal and gone
beyond the last entry in the collection of data.
It returns true if the iterator has another entry to return.
public T next()
It retrieves the next entry in the collection and advances this iterator
by one position.
It returns a reference to the next entry in the iteration, if one exists
It throws NoSuchElementException if the iterator had reached the
end already, that is, if hasNext() is false.
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Explanation
public boolean hasNext()
It detects whether this iterator has completed its traversal and gone
beyond the last entry in the collection of data.
It returns true if the iterator has another entry to return.
public T next()
It retrieves the next entry in the collection and advances this iterator
by one position.
It returns a reference to the next entry in the iteration, if one exists
It throws NoSuchElementException if the iterator had reached the
end already, that is, if hasNext() is false.
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Explanation
public boolean hasNext()
It detects whether this iterator has completed its traversal and gone
beyond the last entry in the collection of data.
It returns true if the iterator has another entry to return.
public T next()
It retrieves the next entry in the collection and advances this iterator
by one position.
It returns a reference to the next entry in the iteration, if one exists
It throws NoSuchElementException if the iterator had reached the
end already, that is, if hasNext() is false.
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Explanation
public boolean hasNext()
It detects whether this iterator has completed its traversal and gone
beyond the last entry in the collection of data.
It returns true if the iterator has another entry to return.
public T next()
It retrieves the next entry in the collection and advances this iterator
by one position.
It returns a reference to the next entry in the iteration, if one exists
It throws NoSuchElementException if the iterator had reached the
end already, that is, if hasNext() is false.
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Explanation
public boolean hasNext()
It detects whether this iterator has completed its traversal and gone
beyond the last entry in the collection of data.
It returns true if the iterator has another entry to return.
public T next()
It retrieves the next entry in the collection and advances this iterator
by one position.
It returns a reference to the next entry in the iteration, if one exists
It throws NoSuchElementException if the iterator had reached the
end already, that is, if hasNext() is false.
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Explanation
public void remove()
It removes from the collection of data the last entry that next()
returned.
Precondition: next() has been called, and remove() has not been
called since then.
It throws IllegalStateException if next() has not been
called, or if remove() was called already after the last
call to next().
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Explanation
public void remove()
It removes from the collection of data the last entry that next()
returned.
Precondition: next() has been called, and remove() has not been
called since then.
It throws IllegalStateException if next() has not been
called, or if remove() was called already after the last
call to next().
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Explanation
public void remove()
It removes from the collection of data the last entry that next()
returned.
Precondition: next() has been called, and remove() has not been
called since then.
It throws IllegalStateException if next() has not been
called, or if remove() was called already after the last
call to next().
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20. Images/cinvestav-
Effect in a list
Before next()
Joes Piotor Iterator cursor Jen Jess Marius
After next()
Joes Piotor Jen Iterator cursor Jess Marius
Effect of remove()
Joes Piotor Iterator cursor Jess Marius
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21. Images/cinvestav-
Effect in a list
Before next()
Joes Piotor Iterator cursor Jen Jess Marius
After next()
Joes Piotor Jen Iterator cursor Jess Marius
Effect of remove()
Joes Piotor Iterator cursor Jess Marius
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22. Images/cinvestav-
Effect in a list
Before next()
Joes Piotor Iterator cursor Jen Jess Marius
After next()
Joes Piotor Jen Iterator cursor Jess Marius
Effect of remove()
Joes Piotor Iterator cursor Jess Marius
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23. Images/cinvestav-
NO FREE LUNCH!!!
Remark
Some details of using an iterator depend on the approach used to
implement the iterator methods.
We can do the following
A possible, but not optimal, way to provide an ADT with traversal
operations is to define them as ADT operations.
For example, if ListInterface extends Iterator, a list object would
have iterator methods as well as list methods.
PROBLEM!!! What if you want to have two or more iterators over the
object list making different things at the same time!!!
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24. Images/cinvestav-
NO FREE LUNCH!!!
Remark
Some details of using an iterator depend on the approach used to
implement the iterator methods.
We can do the following
A possible, but not optimal, way to provide an ADT with traversal
operations is to define them as ADT operations.
For example, if ListInterface extends Iterator, a list object would
have iterator methods as well as list methods.
PROBLEM!!! What if you want to have two or more iterators over the
object list making different things at the same time!!!
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25. Images/cinvestav-
NO FREE LUNCH!!!
Remark
Some details of using an iterator depend on the approach used to
implement the iterator methods.
We can do the following
A possible, but not optimal, way to provide an ADT with traversal
operations is to define them as ADT operations.
For example, if ListInterface extends Iterator, a list object would
have iterator methods as well as list methods.
PROBLEM!!! What if you want to have two or more iterators over the
object list making different things at the same time!!!
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26. Images/cinvestav-
NO FREE LUNCH!!!
Remark
Some details of using an iterator depend on the approach used to
implement the iterator methods.
We can do the following
A possible, but not optimal, way to provide an ADT with traversal
operations is to define them as ADT operations.
For example, if ListInterface extends Iterator, a list object would
have iterator methods as well as list methods.
PROBLEM!!! What if you want to have two or more iterators over the
object list making different things at the same time!!!
11 / 79

27. Images/cinvestav-
Outline
1 Iterators
Interface
Separate and Inner Class Iterator
2 Introduction
Linked Representation
Memory Layout
3 Operations
IsEmpty()
size()
Get(Index)
Remove
Add
4 Can we simplify the code?
5 Other data structures based in the Linked List
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28. Images/cinvestav-
Solution
We can have
Separate class iterator
Inner Class Iterator
For separate class iterator, we have stuff like this
Iterator<String> nameIterator = new
SeparateIterator<String>(nameList);
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Solution
We can have
Separate class iterator
Inner Class Iterator
For separate class iterator, we have stuff like this
Iterator<String> nameIterator = new
SeparateIterator<String>(nameList);
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Solution
We can have
Separate class iterator
Inner Class Iterator
For separate class iterator, we have stuff like this
Iterator<String> nameIterator = new
SeparateIterator<String>(nameList);
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Example
Problem Number of times Any Name Appears in the list
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Multiple Iterators
Thus
External Iterators provides a solution to multiple iterators
However
Huge Problem
We can only access the list through the public methods:
What if they are not enough?
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Multiple Iterators
Thus
External Iterators provides a solution to multiple iterators
However
Object Iterator from
separate class
iterators
Object from class list
list
Lou
Peg
Meg
ME
Iterator
Cursor
Next
Position2
Huge Problem
We can only access the list through the public methods:
What if they are not enough?
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Separate Iterator Code
Code
import java . u t i l . I t e r a t o r ;
import java . u t i l . NoSuchElementException ;
p u b l i c c l a s s S e p a r a t e I t e r a t o r <Item>
implements I t e r a t o r <Item> {
p r i v a t e L i n e a r L i s t <Item> l i s t ;
// p o s i t i o n of entry l a s t r et urn ed by next ()
p r i v a t e i n t n e x t P o s i t i o n ;
// needed by remove
p r i v a t e boolean wasNextCalled ;
p u b l i c S e p a r a t e I t e r a t o r ( L i s t L i s t <Item> a L i s t ) {
// A l l that i t i m p l i e s
} // end c o n s t r u c t o r
< Implementations of the methods hasNext , . . .
next , and remove go here > . . .
} // end S e p a r a t e I t e r a t o r
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We need a better solution!!!
Declare a inner class
So you can have direct access to the protected or private elements in the
object!!!
Actually you have something like this
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36. Images/cinvestav-
We need a better solution!!!
Declare a inner class
So you can have direct access to the protected or private elements in the
object!!!
Actually you have something like this
Object Iterator from
Inner class
iterators
Object from class
array list
Lou Peg Meg ME
nextPosition2
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Inner Class Code
Code
import j a v a . u t i l . I t e r a t o r ;
import j a v a . u t i l . NoSuchElementException ;
p u b l i c c l a s s A r r a y L i s t W i t h I t e r a t o r <T>
implements L i s t W i t h I t e r a t o r I n t e r f a c e <T> {
// ALL the code f o r a r r a y l i n e a r l i s t
p r i v a t e c l a s s I t e r a t o r F o r A r r a y L i s t
implements I t e r a t o r <T> {
p r i v a t e i n t nextIndex ;
p r i v a t e boolean wasNextCalled ;
p r i v a t e I t e r a t o r F o r A r r a y L i s t () {
nextIndex = 0;
wasNextCalled = f a l s e ;
} // end d e f a u l t c o n s t r u c t o r
< Implementations of the methods i n the
i n t e r f a c e I t e r a t o r go here > . . . }
// end I t e r a t o r F o r A r r a y L i s t
} // end A r r a y L i s t W i t h I t e r a t o r
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38. Images/cinvestav-
So, we have...
Advantages
It is a way of logically grouping classes that are only used in one place.
It increases encapsulation
It can lead to more readable and maintainable code.
Example
ArrayListWithIterator<Integers> SOME = new
ArrayListWithIterator<Integers>();
ArrayListWithIterator.IteratorForArrayList fl = SOME. new
IteratorForArrayList();
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39. Images/cinvestav-
So, we have...
Advantages
It is a way of logically grouping classes that are only used in one place.
It increases encapsulation
It can lead to more readable and maintainable code.
Example
ArrayListWithIterator<Integers> SOME = new
ArrayListWithIterator<Integers>();
ArrayListWithIterator.IteratorForArrayList fl = SOME. new
IteratorForArrayList();
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40. Images/cinvestav-
So, we have...
Advantages
It is a way of logically grouping classes that are only used in one place.
It increases encapsulation
It can lead to more readable and maintainable code.
Example
ArrayListWithIterator<Integers> SOME = new
ArrayListWithIterator<Integers>();
ArrayListWithIterator.IteratorForArrayList fl = SOME. new
IteratorForArrayList();
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41. Images/cinvestav-
So, we have...
Advantages
It is a way of logically grouping classes that are only used in one place.
It increases encapsulation
It can lead to more readable and maintainable code.
Example
ArrayListWithIterator<Integers> SOME = new
ArrayListWithIterator<Integers>();
ArrayListWithIterator.IteratorForArrayList fl = SOME. new
IteratorForArrayList();
19 / 79

42. Images/cinvestav-
Outline
1 Iterators
Interface
Separate and Inner Class Iterator
2 Introduction
Linked Representation
Memory Layout
3 Operations
IsEmpty()
size()
Get(Index)
Remove
Add
4 Can we simplify the code?
5 Other data structures based in the Linked List
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43. Images/cinvestav-
Linked Representation
Storage
List elements are stored, in memory, in an arbitrary order.
How you move through it
Explicit information (called a link) is used to go from one element to the
next.
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Linked Representation
Storage
List elements are stored, in memory, in an arbitrary order.
How you move through it
Explicit information (called a link) is used to go from one element to the
next.
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45. Images/cinvestav-
Outline
1 Iterators
Interface
Separate and Inner Class Iterator
2 Introduction
Linked Representation
Memory Layout
3 Operations
IsEmpty()
size()
Get(Index)
Remove
Add
4 Can we simplify the code?
5 Other data structures based in the Linked List
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46. Images/cinvestav-
Memory Layout
We have the following
C A E D B
firstNode
First
Last pointer (or link) from E is null
Thus
You can use a variable firstNode to get to the first element in the Linked
List.
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Memory Layout
We have the following
C A E D B
firstNode
First
Last pointer (or link) from E is null
Thus
You can use a variable firstNode to get to the first element in the Linked
List.
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48. Images/cinvestav-
Memory Layout
We have the following
C A E D B
firstNode
First
Last pointer (or link) from E is null
Thus
You can use a variable firstNode to get to the first element in the Linked
List.
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49. Images/cinvestav-
Normal Way To Draw A Linked List
Example
CA EDB
firstNode
Link or pointer field of node
Data field of node
NULL
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50. Images/cinvestav-
Actually, we know this as a Chain
First
A chain is a linked list in which each node represents one element.
Second
There is a link or pointer from one element to the next.
Third
The last node has a null pointer.
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51. Images/cinvestav-
Actually, we know this as a Chain
First
A chain is a linked list in which each node represents one element.
Second
There is a link or pointer from one element to the next.
Third
The last node has a null pointer.
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52. Images/cinvestav-
Actually, we know this as a Chain
First
A chain is a linked list in which each node represents one element.
Second
There is a link or pointer from one element to the next.
Third
The last node has a null pointer.
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53. Images/cinvestav-
Code for ChainNode
Code
package L i n e a r L i s t ;
// Using Generic in Java
c l a s s ChainNode<Item>{
// package data members
protected Item element ;
protected ChainNode next ;
// c o n s t r u c t o r s and methods come here
}
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54. Images/cinvestav-
The Constructors for ChainNode
A classic one
package L i n e a r L i s t ;
// Using Generic in Java
p u b l i c ChainNode (){
// Set the next node
t h i s . element = n u l l ;
t h i s . next = n u l l ;
}
p u b l i c ChainNode ( Item elem ){
// Set element
t h i s . element = elem ;
t h i s . next = n u l l ;
}
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What about the Class Chain?
Code
/∗∗ l i n k e d implementation of L i n e a r L i s t ∗/
package i n f r a s t r u c t u r e s ;
import java . u t i l . ∗ ; // has I t e r a t o r
p u b l i c c l a s s Chain<Item> implements L i n e a r L i s t <Item>
{
// data members
protected ChainNode<Item> f i r s t N o d e ;
protected i n t s i z e ;
// methods of Chain come here
}
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56. Images/cinvestav-
In addition!!! Constructors!!!
Code
p u b l i c Chain<Item> ( i n t i n i t i a l C a p a c i t y )
{
// the d e f a u l t i n i t i a l v a l u e s of f i r s t N o d e and s i z e
// are n u l l and 0 , r e s p e c t i v e l y
}
A simple example
public Chain<Item> ()
{
this.firstNode = new ChainNode<Item>();
this.size = 0;
}
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57. Images/cinvestav-
In addition!!! Constructors!!!
Code
p u b l i c Chain<Item> ( i n t i n i t i a l C a p a c i t y )
{
// the d e f a u l t i n i t i a l v a l u e s of f i r s t N o d e and s i z e
// are n u l l and 0 , r e s p e c t i v e l y
}
A simple example
public Chain<Item> ()
{
this.firstNode = new ChainNode<Item>();
this.size = 0;
}
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58. Images/cinvestav-
Outline
1 Iterators
Interface
Separate and Inner Class Iterator
2 Introduction
Linked Representation
Memory Layout
3 Operations
IsEmpty()
size()
Get(Index)
Remove
Add
4 Can we simplify the code?
5 Other data structures based in the Linked List
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59. Images/cinvestav-
IsEmpty()
Really Simple Code
/∗∗ @return true i f f l i s t i s empty ∗/
p u b l i c boolean isEmpty ()
{ r e t u r n s i z e == 0;}
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60. Images/cinvestav-
Outline
1 Iterators
Interface
Separate and Inner Class Iterator
2 Introduction
Linked Representation
Memory Layout
3 Operations
IsEmpty()
size()
Get(Index)
Remove
Add
4 Can we simplify the code?
5 Other data structures based in the Linked List
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61. Images/cinvestav-
size()
Really Simple Code
/∗∗ @return c u r r e n t number of elements in l i s t ∗/
p u b l i c i n t s i z e ()
{ r e t u r n s i z e ;}
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62. Images/cinvestav-
Outline
1 Iterators
Interface
Separate and Inner Class Iterator
2 Introduction
Linked Representation
Memory Layout
3 Operations
IsEmpty()
size()
Get(Index)
Remove
Add
4 Can we simplify the code?
5 Other data structures based in the Linked List
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63. Images/cinvestav-
Operations: Get
Example
CA EDB
firstNode
Link or pointer field of node
Data field of node
NULL
What to do to implement Get
1 Check Index
2 Move to the correct position
For example: TempNode = firstNode.next.next.next.
You actually use a loop.
3 return TempNode.element
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64. Images/cinvestav-
Operations: Get
Example
CA EDB
firstNode
Link or pointer field of node
Data field of node
NULL
What to do to implement Get
1 Check Index
2 Move to the correct position
For example: TempNode = firstNode.next.next.next.
You actually use a loop.
3 return TempNode.element
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65. Images/cinvestav-
Process
Check Index
0 ≤ index ≤ size − 1 (1)
Negate the statement to use it
How?
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66. Images/cinvestav-
Process
Check Index
0 ≤ index ≤ size − 1 (1)
Negate the statement to use it
How?
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67. Images/cinvestav-
Move to the correct place
How?
CA EDB
firstNode NULL
TempNode=firstNode
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68. Images/cinvestav-
Move to the correct place
Index == 2
CA EDB
firstNode NULL
TempNode=firstNode
index==2
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69. Images/cinvestav-
Move to the correct place
Index == 2
CA EDB
firstNode NULL
TempNode=TempNode.next
index==2
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70. Images/cinvestav-
Move to the correct place
Index == 2
CA EDB
firstNode NULL
TempNode=TempNode.next
index==2
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71. Images/cinvestav-
Move to the correct place
Index == 2
CA EDB
firstNode NULL
return TempNode.element
index==2
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72. Images/cinvestav-
Code
Here is the method
p u b l i c <Item> get ( i n t index ){
ChainNode<Item> TempNode ;
//Check always
i f ( t h i s . s i z e == 0) r e t u r n n u l l ;
i f ( index <0 | | index >t h i s . s i z e −1){
System . out . p r i n t l n ( " Index ␣ out ␣ of ␣bound " ) ;
System . e x i t ( 0 ) ;
}
//Move to the c o r r e c t p o s i t i o n
TempNode = t h i s . f i r s t N o d e ;
f o r ( i n t i =0 ; i <index ; i ++){
TempNode = TempNode . next ;
}
r e t u r n TempNode . element ;
}
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73. Images/cinvestav-
Outline
1 Iterators
Interface
Separate and Inner Class Iterator
2 Introduction
Linked Representation
Memory Layout
3 Operations
IsEmpty()
size()
Get(Index)
Remove
Add
4 Can we simplify the code?
5 Other data structures based in the Linked List
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74. Images/cinvestav-
Now, Remove
We have two cases
Any ideas?
Case I
Removing from the beginning.
Case II
Remove from the middle.
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75. Images/cinvestav-
Now, Remove
We have two cases
Any ideas?
Case I
Removing from the beginning.
Case II
Remove from the middle.
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76. Images/cinvestav-
Now, Remove
We have two cases
Any ideas?
Case I
Removing from the beginning.
Case II
Remove from the middle.
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77. Images/cinvestav-
Case I: Remove(0)
Process
1 if index == 0 do
1 TempNode = firstNode
2 firstNode=firstNode.next
3 TempNode.next=NULL
4 return TempNode.element
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78. Images/cinvestav-
Case I: Remove(0)
Process
1 if index == 0 do
1 TempNode = firstNode
2 firstNode=firstNode.next
3 TempNode.next=NULL
4 return TempNode.element
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79. Images/cinvestav-
Case I: Remove(0)
Process
1 if index == 0 do
1 TempNode = firstNode
2 firstNode=firstNode.next
3 TempNode.next=NULL
4 return TempNode.element
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80. Images/cinvestav-
Case I: Remove(0)
Process
1 if index == 0 do
1 TempNode = firstNode
2 firstNode=firstNode.next
3 TempNode.next=NULL
4 return TempNode.element
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81. Images/cinvestav-
Case I: Remove(0)
Process
1 if index == 0 do
1 TempNode = firstNode
2 firstNode=firstNode.next
3 TempNode.next=NULL
4 return TempNode.element
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82. Images/cinvestav-
Process
TempNode=firstNode
CA EDB
firstNode NULL
TempNode=firstNode
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83. Images/cinvestav-
Process
firstNode=firstNode.next
CA EDB
firstNode NULL
TempNode
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84. Images/cinvestav-
Process
TempNode.next=NULL
CA EDB
firstNode NULL
TempNode NULL
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85. Images/cinvestav-
Process
return TempNode.element
CA EDB
firstNode NULL
return TempNode.element
NULL
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Case II: Remove(2)
Process
1 Check Index
2 Starting at the first node
3 TempNode=firstNode;
4 Loop doing
1 beforeNode=TempNode;
2 TempNode=TempNode.next;
5 before.next = TempNode.next
6 TempNode.next = NULL
7 return TempNode.element
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Case II: Remove(2)
Process
1 Check Index
2 Starting at the first node
3 TempNode=firstNode;
4 Loop doing
1 beforeNode=TempNode;
2 TempNode=TempNode.next;
5 before.next = TempNode.next
6 TempNode.next = NULL
7 return TempNode.element
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Case II: Remove(2)
Process
1 Check Index
2 Starting at the first node
3 TempNode=firstNode;
4 Loop doing
1 beforeNode=TempNode;
2 TempNode=TempNode.next;
5 before.next = TempNode.next
6 TempNode.next = NULL
7 return TempNode.element
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Case II: Remove(2)
Process
1 Check Index
2 Starting at the first node
3 TempNode=firstNode;
4 Loop doing
1 beforeNode=TempNode;
2 TempNode=TempNode.next;
5 before.next = TempNode.next
6 TempNode.next = NULL
7 return TempNode.element
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Case II: Remove(2)
Process
1 Check Index
2 Starting at the first node
3 TempNode=firstNode;
4 Loop doing
1 beforeNode=TempNode;
2 TempNode=TempNode.next;
5 before.next = TempNode.next
6 TempNode.next = NULL
7 return TempNode.element
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Case II: Remove(2)
Process
1 Check Index
2 Starting at the first node
3 TempNode=firstNode;
4 Loop doing
1 beforeNode=TempNode;
2 TempNode=TempNode.next;
5 before.next = TempNode.next
6 TempNode.next = NULL
7 return TempNode.element
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Case II: Remove(2)
Process
1 Check Index
2 Starting at the first node
3 TempNode=firstNode;
4 Loop doing
1 beforeNode=TempNode;
2 TempNode=TempNode.next;
5 before.next = TempNode.next
6 TempNode.next = NULL
7 return TempNode.element
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Case II: Remove(2)
Process
1 Check Index
2 Starting at the first node
3 TempNode=firstNode;
4 Loop doing
1 beforeNode=TempNode;
2 TempNode=TempNode.next;
5 before.next = TempNode.next
6 TempNode.next = NULL
7 return TempNode.element
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Case II: Remove(2)
Process
1 Check Index
2 Starting at the first node
3 TempNode=firstNode;
4 Loop doing
1 beforeNode=TempNode;
2 TempNode=TempNode.next;
5 before.next = TempNode.next
6 TempNode.next = NULL
7 return TempNode.element
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Process
TempNode=firstNode
CA EDB
firstNode NULL
TempNode=firstNode
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Process: index == 2
beforeNode=TempNode;
TempNode=TempNode.next;
CA EDB
firstNode NULL
beforeNode=TempNode TempNode=TempNode.next
index==2
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Process: index == 2
beforeNode=TempNode;
TempNode=TempNode.next;
CA EDB
firstNode NULL
beforeNode=TempNode TempNode=TempNode.next
index==2
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Process: index == 2
before.next = TempNode.next
CA EDB
firstNode NULL
beforeNode.next=TempNode.next
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Process: index == 2
TempNode.next = NULL
CA EDB
firstNode NULL
TempNode=TempNode.next
NULL
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Process: index == 2
TempNode.next = NULL
CA EDB
firstNode NULL
return TempNode.element
NULL
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Outline
1 Iterators
Interface
Separate and Inner Class Iterator
2 Introduction
Linked Representation
Memory Layout
3 Operations
IsEmpty()
size()
Get(Index)
Remove
Add
4 Can we simplify the code?
5 Other data structures based in the Linked List
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Now, Add
We have four cases
Any ideas?
Case I
The Chain is Empty
Case II
Add at the beginning.
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Now, Add
We have four cases
Any ideas?
Case I
The Chain is Empty
Case II
Add at the beginning.
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Now, Add
We have four cases
Any ideas?
Case I
The Chain is Empty
Case II
Add at the beginning.
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Now, Add
We have four cases
Any ideas?
Case III
Add at the middle.
Case IV
Add at the end.
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Now, Add
We have four cases
Any ideas?
Case III
Add at the middle.
Case IV
Add at the end.
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Now, Add
We have four cases
Any ideas?
Case III
Add at the middle.
Case IV
Add at the end.
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Why?
Think About it!!!
Remember you have a sequential access.
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Add at an empty list
Steps
1 Create a node to store the element, NewNode
2 Then assign firstNode = NewNode
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Add at an empty list
Steps
1 Create a node to store the element, NewNode
2 Then assign firstNode = NewNode
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Add at an empty list
Steps
1 Create a node to store the element, NewNode
2 Then assign firstNode = NewNode
firstNode
K
NULL
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Add At the Beginning
Steps
1 Create a node to store the element, NewNode
2 Do NewNode.next = firstNode
3 Then reassign firstNode = NewNode
4 Then, size = size +1
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Add At the Beginning
Steps
1 Create a node to store the element, NewNode
2 Do NewNode.next = firstNode
3 Then reassign firstNode = NewNode
4 Then, size = size +1
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Add At the Beginning
Steps
1 Create a node to store the element, NewNode
2 Do NewNode.next = firstNode
3 Then reassign firstNode = NewNode
4 Then, size = size +1
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Add At the Beginning
Steps
1 Create a node to store the element, NewNode
2 Do NewNode.next = firstNode
3 Then reassign firstNode = NewNode
4 Then, size = size +1
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Add At the Beginning
Steps
1 Create a node to store the element, NewNode
2 Do NewNode.next = firstNode
3 Then reassign firstNode = NewNode
4 Then, size = size +1
CA EDB
firstNode
NULL
K
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What about the other case?
Do you have an idea?
Add at the Middle.
Add at the end.
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What about the other methods?
Linear List
AbstractDataType LinearList
{
instances
ordered finite collections of zero or more elements
operations
isEmpty(): return true iff the list is empty, false otherwise
size(): return the list size (i.e., number of elements in the list)
get(index): return the element with the “index” index
indexOf(x): return the index of the first occurrence of x in the list, return -1
if x is not in the list
remove(index): remove and return the indexth element, elements with higher
index have their index reduced by 1
add(theIndex, x): insert x as the index of th element, elements with
theIndex ≥ index have their index increased by 1
output(): output the list elements from left to right
}
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Complexity of Linked List
We have
Dynamic Array Linked List
Amortized Analysis
Indexing O (1) O (n)
Search O (n) O (n)
Add/Remove at the beginning O (n) O (1)
Add/Remove at the middle O (n) Search Time
+O (1)
Space Complexity O (n) O (n)
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Average Performance with Each Implementation on a Slow
Machine!!!
40,000 Operations each type on a 350Mhz PC
Operation FastArrayLinearList Chain
average get 5.6 ms 157 sec
average adds 5.8 sec 115 sec
average removes 5.8 sec 157 sec
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Can we simplify the code?
How?
We would like to simplify the code.... How?
What about
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Can we simplify the code?
How?
We would like to simplify the code.... How?
What about
CA EDB
headerNode NULL
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Can we simplify the code?
Then, the empty list looks like
headerNode
Thus
This simplify a lot the code because everything is a middle node
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Can we simplify the code?
Then, the empty list looks like
headerNode
Thus
This simplify a lot the code because everything is a middle node
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Circular List
Circular List
CA EDB
firstNode lastNode
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Here, we need to have the following changes
We need to add the following to the class
/∗∗ l i n k e d implementation of L i n e a r L i s t ∗/
package i n f r a s t r u c t u r e s ;
import java . u t i l . ∗ ; // has I t e r a t o r
p u b l i c c l a s s Chain<Item> implements L i n e a r L i s t <Item>
{
// data members
protected ChainNode<Item> f i r s t N o d e ;
protected ChainNode<Item> lastNode ;
protected i n t s i z e ;
// methods of Chain come here
}
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Example of add(index) at the end
Process
Check if (index==size-1)
Next
Make the lastNode.next = TempNode
Then
TempNode.next = firstNode
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Example of add(index) at the end
Process
Check if (index==size-1)
Next
Make the lastNode.next = TempNode
Then
TempNode.next = firstNode
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Example of add(index) at the end
Process
Check if (index==size-1)
Next
Make the lastNode.next = TempNode
Then
TempNode.next = firstNode
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Example of add(index) at the end
Finally
lastNode = TempNode
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Circular List
Add at the end
CA EDB
firstNode lastNode
F
lastNode.next = TempNode
TempNode
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Circular List
Add at the end
CA EDB
firstNode
lastNode
F
TempNode.next = firstNode TempNode
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Circular List
Add at the end
CA EDB
firstNode
F
lastNode=TempNode
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We have other representations for the lists
Doubly Linked List
You have two chain list going through the nodes.
It has a firstNode
It has a lastNode
Doubly Linked Circular List
You have two chain list going through the nodes.
It has a firstNode
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We have other representations for the lists
Doubly Linked List
You have two chain list going through the nodes.
It has a firstNode
It has a lastNode
Doubly Linked Circular List
You have two chain list going through the nodes.
It has a firstNode
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Doubly Linked List
Doubly Linked List
CA EDB
firstNode lastNode
NULL
NULL
What about the changes here
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Doubly Linked Circular List
Doubly Linked Circular List
CA EDB
firstNode
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Where does Java has all these things?
Package
java.util.LinkedList
There you have
It has the Linked implementation of a linear list.
It has the doubly linked circular list with header node.
It Has all methods of LinearList plus many more.
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Where does Java has all these things?
Package
java.util.LinkedList
There you have
It has the Linked implementation of a linear list.
It has the doubly linked circular list with header node.
It Has all methods of LinearList plus many more.
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Where does Java has all these things?
Package
java.util.LinkedList
There you have
It has the Linked implementation of a linear list.
It has the doubly linked circular list with header node.
It Has all methods of LinearList plus many more.
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