Data Structure HKOI training 2009 3/4/2010 So Pak Yeung

Data StructureData StructureHKOI training 2009HKOI training 2009

3/4/20103/4/2010So Pak YeungSo Pak Yeung

What is data structure?What is data structure?a particular way of storing and organia particular way of storing and organizing data in a computer so that it can zing data in a computer so that it can be used efficiently. be used efficiently.

From wikipediaFrom wikipedia

OutlineOutline

StackStack QueueQueue Linked listLinked list

StackStack

Last In First Out (LIFO)Last In First Out (LIFO) Operations:Operations:

• PushPush• PopPop

Stack - PushStack - Push

Put an element on the top of the stackPut an element on the top of the stack

if (top==MAX_SIZE) //stack is fullif (top==MAX_SIZE) //stack is full output “error: stack overflow”output “error: stack overflow”

elseelse stack[top++] = data;stack[top++] = data;

Stack - PopStack - Pop

Remove the element on the top of the stackRemove the element on the top of the stack

if (top==0) //the stack is emptyif (top==0) //the stack is emptyoutput “Error: stack underflow”output “Error: stack underflow”

else{ else{ // tmp = stack[--top]; // tmp = stack[--top]; --top;--top;

}}

QueueQueue

First In First Out (FIFO)First In First Out (FIFO) Operations:Operations:

• EnqueueEnqueue• DequeueDequeue

Queue - EnqueueQueue - Enqueue

Add an element at the end of the queueAdd an element at the end of the queue

if (e == MAX)if (e == MAX)output “Error”output “Error”

elseelsequeue[e++] = data;queue[e++] = data;

Queue: DequeueQueue: Dequeue

Remove the element at the front of the queueRemove the element at the front of the queue

if (f==e) //empty queueif (f==e) //empty queueoutput “error”output “error”

else{else{// tmp = queue[f];// tmp = queue[f];++f;++f;

}}

QueueQueue

Not efficient in terms of memoryNot efficient in terms of memory Improvement:Improvement:

• Using linked list to implementUsing linked list to implement• Circular QueueCircular Queue

Linked ListLinked List

Data + PointersData + Pointers Operations:Operations:

• InsertionInsertion• DeletionDeletion

Linked ListLinked List

data1 data2 data3 data4

nullhead

Linked List - InsertionLinked List - Insertion

Assume we add a node after node 2Assume we add a node after node 2

data1 data2 data3 data4

nullhead

Linked List - InsertionLinked List - Insertion

data1 data2 data3 data4

nullnew data

head

Linked List - InsertionLinked List - Insertion

data1 data2 data3 data4

nullnew data

head

Linked List - InsertionLinked List - Insertion

data1 data2 data3 data4

nullnew data

head

Linked List - InsertionLinked List - Insertion

node* tmp = new node;node* tmp = new node;tmp->data = new_data;tmp->data = new_data;tmp->next = target->next;tmp->next = target->next;target->next = tmp;target->next = tmp;

Linked List - DeletionLinked List - Deletion

Assume we delete node 3Assume we delete node 3

data1 data2 data3 data4

nullhead

Linked List - DeletionLinked List - Deletion

data1 data2 data3 data4

nulltmphead

Linked List - DeletionLinked List - Deletion

data1 data2 data3 data4

nulltmphead

Linked List - DeletionLinked List - Deletion

data1 data2 data4

nullhead

Linked List - DeletionLinked List - Deletion

node* tmp = target->next;node* tmp = target->next;target->next = tmp->next;target->next = tmp->next;delete tmp;delete tmp;

Linked ListLinked List

It is so troublesome when we try to It is so troublesome when we try to delete the first node / insert before delete the first node / insert before the first nodethe first node

Dummy nodeDummy node Doubly Linked ListDoubly Linked List

Linked ListLinked List

data1 data2 data3 data4

null

head

Types of Linked ListTypes of Linked List

Singly-Linked ListSingly-Linked List Doubly-Linked ListDoubly-Linked List Circularly-Linked ListCircularly-Linked List

Questions?Questions?