CSC 1351: Advanced Java - Interdisciplinary -...

CSC 1351: Advanced JavaLinked lists, Stacks, Queues

Dr Frank [email protected]

Center for Computation and TechnologyLouisiana State University, Baton Rouge, LA

Mar 16 2017

Frank Loffler CSC 1351: Advanced Java Mar 16 2017

Today: Basic Data Structures (other than arrays)

Linked Lists

singly linked listsdoubly linked lists

Queues

Stacks

Reading until Tuesday: Chapters 15.1, 15.2, 15.5, 16.1, 16.3QUIZ!


Linked Lists


Linked Lists

Linked List (LL):

Collection of nodes containing

some datasome reference(s) (links) to other nodes

Linked list example (singly linked list):

12 99 37


Linked lists: Advantages/Disadvantages

Pros

can grow dynamically (although arrays can too)does not need contiguous memorysome operations fast (e.g., inserting element in some cases)item data not necessarily uniform

Cons

references add memory overheadsome operations slow, e.g., random look-upmaybe only able to traverse one way


Linked list tips

Think of special cases

list emptywhat if there is only one element?

Draw diagrams if unsure.


List Variations

Singly linked lists

Doubly linked lists

Circular linked lists (both singly and doubly)


List Operations

Creation

Insertion

Removal

Deletion

Look-up / Retrieval


Singly LL Operations: Creation

Reduces to the question: How does an empty list look like?


Singly LL Operations: Insert

Inserting first element...

12 99



Inserting first element...

12

99



Inserting next element...

12 99


Singly LL Operations: Removal

Removing element “99”

12 99



Removing element “99”, requires look-up of element “12”

12 99



Removing last element “12”

12

99



Removing last element “12”

12 99


Singly LL Operations: Deletion

Remove all elements until list empty, clean up


Singly LL Operations: Look-up / Retrieval

12 99 37

O(N)


Doubly Linked Lists


Doubly linked list example

12 99 37


Doubly LL Operations: Creation

An empty doubly linked list:


Doubly LL Operations: Insert

Inserting elements:

12

99


Doubly LL Operations: Insert

Inserting elements:

12 99


Doubly LL Operations: Removal

Removing element “99”:

12 99



Removing element “99”: does not require expensive look-up:

12 99



Removing element “99”: does not require expensive look-up:

12

99




12

99




12 99


Doubly LL Operations: Deletion

Remove all elements until list empty, clean up


Doubly LL Operations: Look-up / Retrieval

12 99 37

still O(N), but access to end faster


Lab today

Implement a doubly linked list.

Don’t use any of the Java-provided List classes.

Use provided “Node” class

No need for full LL interface - “just” the methods mentioned in thelab description


Queues


Queue

Fundamental data structure

Container of elements

Elements inserted and removed according to theFirst-In First-Out FIFO principle

Insertion of elements always possible (assuming enough space)

Removal only possible for “oldest” element

Elements only enter at “rear” and only leave at the “front”

Implementation usually using arrays or linked lists


Queue Operations / Abstract Data Type

enqueue(): insert element at rear (“push”)

dequeue(): remove element at front (“pop”), error if queue empty

front(): return (but not remove) a reference to the front elementerror if empty

size(): get number of elements

empty(): “true” if queue empty, “false” otherwise


Deque

Similar to queue, but with two “open ends”

Pronounced “deck” (like a deck of cards, and is similar to it)

Often implemented using doubly linked list


Deque Operations / Abstract Data Type

insertFront(): Insert element at front

insertBack(): Insert element at back

eraseFront(): Remove first element, error if empty

eraseBack(): Remove last element, error if empty

front(): Return first element, error if empty

back(): Return last element, error if empty

size(): Return number of elements in deque

empty(): “true” if deque empty, “false” otherwise


Stacks


Stacks

Fundamental data structure

Container of elements

Elements inserted and removed according to the Last-In First-OutLIFO principle

Insertion of elements always possible (assuming enough space)

Removal only possible for “newest” element

Elements only enter on “top” and only leave from there

Implementation usually using arrays or linked lists


Stack Operations / Abstract Data Type

push(): Insert element at top of stack

pop(): Remove element from top of stack, error if empty

top(): Return reference to element on top, error if empty

size(): Return number of elements

empty(): “true” if stack empty, “false” otherwise


Stack Applications

Among the most common data structures

Especially useful in partsing and translation of computer languages,mathematics, and other formal notations

Parentheses matchingCompilers


Using Stacks in Function Calls

Collection of information representing a function call → activation

Computer systems use runtime activation stack to keep track of thatinformation (return addresses, parameters, local variables)

Each function call results in push onto stack

Each function returns results in pop from stack

Using stack can help with debugging: backtrace

Turns recursive functions into series of stack pushes

Recursive functions and require a lot of stack memory... and can run out of it → stack overflow


Exercise I

Stack S initially empty

In unspecified order:

25 push operations

12 top operations

10 pop operations, of which 3 generated StackEmpty exception(caught and ignored)

What is the current size of S?

25− (10− 3) = 18


Exercise II

Describe the output of the following operations on a stack:

push(5)

push(3)

print pop()

push(2)

push(8)

print pop()

print pop()

push(9)

push(1)

print pop()

push(7)

print pop()

print pop()

3, 8, 2, 1, 7, 9


Exercise II


push(5)

push(3)

print pop()

push(2)

push(8)

print pop()

print pop()

push(9)

push(1)

print pop()

push(7)

print pop()

print pop()

3,

8, 2, 1, 7, 9


Exercise II


push(5)

push(3)

print pop()

push(2)

push(8)

print pop()

print pop()

push(9)

push(1)

print pop()

push(7)

print pop()

print pop()

3, 8,

2, 1, 7, 9


Exercise II


push(5)

push(3)

print pop()

push(2)

push(8)

print pop()

print pop()

push(9)

push(1)

print pop()

push(7)

print pop()

print pop()

3, 8, 2,

1, 7, 9


Exercise II


push(5)

push(3)

print pop()

push(2)

push(8)

print pop()

print pop()

push(9)

push(1)

print pop()

push(7)

print pop()

print pop()

3, 8, 2, 1,

7, 9


Exercise II


push(5)

push(3)

print pop()

push(2)

push(8)

print pop()

print pop()

push(9)

push(1)

print pop()

push(7)

print pop()

print pop()

3, 8, 2, 1, 7,

9


Exercise II


push(5)

push(3)

print pop()

push(2)

push(8)

print pop()

print pop()

push(9)

push(1)

print pop()

push(7)

print pop()

print pop()

3, 8, 2, 1, 7, 9Frank Loffler CSC 1351: Advanced Java Mar 16 2017

Exercise III

Describe the output of the following operations on a queue:

enqueue(5)

enqueue(3)

print dequeue()

enqueue(2)

enqueue(8)

print dequeue()

print dequeue()

enqueue(9)

print dequeue()

print dequeue()

print dequeue()

5, 3, 2, 8, 9, ERROR


Exercise III


enqueue(5)

enqueue(3)

print dequeue()

enqueue(2)

enqueue(8)

print dequeue()

print dequeue()

enqueue(9)

print dequeue()

print dequeue()

print dequeue()

5,

3, 2, 8, 9, ERROR


Exercise III


enqueue(5)

enqueue(3)

print dequeue()

enqueue(2)

enqueue(8)

print dequeue()

print dequeue()

enqueue(9)

print dequeue()

print dequeue()

print dequeue()

5, 3,

2, 8, 9, ERROR


Exercise III


enqueue(5)

enqueue(3)

print dequeue()

enqueue(2)

enqueue(8)

print dequeue()

print dequeue()

enqueue(9)

print dequeue()

print dequeue()

print dequeue()

5, 3, 2,

8, 9, ERROR


Exercise III


enqueue(5)

enqueue(3)

print dequeue()

enqueue(2)

enqueue(8)

print dequeue()

print dequeue()

enqueue(9)

print dequeue()

print dequeue()

print dequeue()

5, 3, 2, 8,

9, ERROR


Exercise III


enqueue(5)

enqueue(3)

print dequeue()

enqueue(2)

enqueue(8)

print dequeue()

print dequeue()

enqueue(9)

print dequeue()

print dequeue()

print dequeue()

5, 3, 2, 8, 9,

ERROR


Exercise III


enqueue(5)

enqueue(3)

print dequeue()

enqueue(2)

enqueue(8)

print dequeue()

print dequeue()

enqueue(9)

print dequeue()

print dequeue()

print dequeue()

5, 3, 2, 8, 9, ERROR


Exercise IV

Describe the output of the following operations on a deque:

insertFront(3)

insertBack(8)

insertBack(9)

insertFront(5)

print eraseFront()

print eraseBack()

print first()

insertBack(7)

print eraseFront()

print last()

print eraseBack()

5, 9, 3, 3, 7, 7


Exercise IV


insertFront(3)

insertBack(8)

insertBack(9)

insertFront(5)

print eraseFront()

print eraseBack()

print first()

insertBack(7)

print eraseFront()

print last()

print eraseBack()

5,

9, 3, 3, 7, 7


Exercise IV


insertFront(3)

insertBack(8)

insertBack(9)

insertFront(5)

print eraseFront()

print eraseBack()

print first()

insertBack(7)

print eraseFront()

print last()

print eraseBack()

5, 9,

3, 3, 7, 7


Exercise IV


insertFront(3)

insertBack(8)

insertBack(9)

insertFront(5)

print eraseFront()

print eraseBack()

print first()

insertBack(7)

print eraseFront()

print last()

print eraseBack()

5, 9, 3,

3, 7, 7


Exercise IV


insertFront(3)

insertBack(8)

insertBack(9)

insertFront(5)

print eraseFront()

print eraseBack()

print first()

insertBack(7)

print eraseFront()

print last()

print eraseBack()

5, 9, 3, 3,

7, 7


Exercise IV


insertFront(3)

insertBack(8)

insertBack(9)

insertFront(5)

print eraseFront()

print eraseBack()

print first()

insertBack(7)

print eraseFront()

print last()

print eraseBack()

5, 9, 3, 3, 7,

7


Exercise IV


insertFront(3)

insertBack(8)

insertBack(9)

insertFront(5)

print eraseFront()

print eraseBack()

print first()

insertBack(7)

print eraseFront()

print last()

print eraseBack()

5, 9, 3, 3, 7, 7


Java Collections Framework


Java Collection Methods

constructor, e.g., new ArrayList<String>()

number of elements: size()

adding element: add()

removing element: remove()

check if collection contains element: contains(...)

string representation of collection: toString()

iterating over elements: iterator()


Java Linked Lists

Inherit Collection

Are doubly-linked lists

Methods:

constructor: new LinkedList<String>()

add element to end: addLast(...) (same as add(...))

add element to front: addFirst(...)

get first element: getFirst()

get last element: getLast()

remove first element: removeFirst()

remove last element: removeLast()

list iterator: listIterator()


Java Stacks

constructor: new Stack<String>()

add to top: push(...)

remove from top: pop() (returns removed element)

look at top element: peek() (does not remove element)


Java Queues

constructor: new Queue<String>()

add to tail: add(...)

remove head: remove() (returns removed element)

look at first element: peek() (does not remove element)


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