BCS2122DCS2192 Data Structure and Algorithm

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BCS2122/DCS2192Data Structure and Algorithm

• Module 5 Stack
• Muhammed Ramiza Ramli

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Stack

• A data structure in which all deletions and
  insertions are allowed only on one end, called
  the top.
• The last entry that is inserted is the first to
  be removed (LIFO)
• A stack is open at one
• end (the top) only. You
• can push entry onto the
• top, or pop the top entry
• out of the stack.

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Example

• Reverse a string
• Check nesting structure
• Undo operation in many editor tools.
• Brackets balancing in compiler
• Stack frame of procedure call
• Hardware stack in CPU

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Undo operation

• In an Excel file, input your data in row
• 100, 200, 300, 400
• Find something wrong, use undo, return to
  previous state
• Operation lists

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LIFO
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Operation with Stack

• Operations on a stack
• pop( ) // remove top
• push( ) // push element
• isEmpty( ) // is it empty?
• For a limited storage
• isFull() // is it full?
• Other needed operations
• Create() //create a stack

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Stack issues

• Implementation issues
• contiguous memory (array)
• Limited size
• Top element can be accessed by referring to
  integer variable
• linked memory (linked list)
• Unlimited size
• Top element can be accessed by referring to the
  pointer

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Stack in Array

• Stack is limited to the size of the array
• Operation can be done on the last element of the
  array.
• Need two field
• Data
• Top index
• Solution Using structure
• typedef struct _stackArray
• int top
• float mark20
• STACK

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Stack in Array create

• Create stack
• Newly created stack should contains no element
  top must be set to non used value like -1
• To create a stack
• STACK markah
• create_stack(markah)
• Function
• void create_stack(STACK s)
• s-gttop -1

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Stack in Array isEmpty

• Its compulsory to check the stack either empty
  or full before pop or push can be done.
• Is it empty function
• int isEmpty(STACK s)
• if(s-gttop lt 0)
• return 1
• else
• return 0
• isEmpty function will return integer value 1 if
  the stack is empty so no pop operation can be
  done.

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Stack in Array isFull

• Is it full function
• int isFull(STACK s,int size)
• if(s-gttop size -1)
• return 1
• else
• return 0
• isFull function will return integer value 1 if
  the stack is full and no more data can be push
  into stack.

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Stack in Array push

• To add a new item into stack
• Its can be done only if the the stack is not
  full.
• Push function
• void push(STACK s, float item)
• s-gttop s-gttop 1
• s-gtmarks-gttop item

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Stack in Array pop

• To remove/get an item from the stack
• Its can be done only if the the stack is not
  empty.
• pop function
• float pop(STACK s)
• float x
• x s-gtmarktop
• s-gttop s-gttop - 1
• return x

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Stack in a linked list

• Data item in the stack is not limited due to the
  node created in linked list dynamic.
• Each stack item is represent in a form of linked
  list node.
• Each node will contain 2 field data and link
  pointer.
• Push or pop can be done in one end of the list
• Top item can be referred by using head pointer.

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Linked list

• Each node / element contains at least 2 fields
• Data
• Link
• Each node contain 1 pointer field
• Link field contains address of the successor node
  (except the last node)

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Illustration of node in linked-list
First part - Data field - Information of element
1ST NODE
2ND NODE
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How to linked list look like in C

• Consist of several connected node
• one node pointer as a header of the list
• nodes
• Head pointer

1st node
2nd node
3rd node
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Declaration

• Declaration of linked list will be using struct
  construct.
• typedef struct node
• int data
• struct node next
• NODE
• we create a new data type NODE as our linked
  lists node
• any new node can be created like normal data type
• NODE x NODE y10 NODE ptr

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Creating a linked list

• Linked list were declared by a head pointer of
  the list
• This pointer will then point to the first node on
  the list and so on.
• If there is no node on the list, head pointer
  will point to NULL (during initialization)

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Node declaration

• Uses static location
• NODE x10
• NODE head, ptr

• Uses dynamic location
• malloc()
• e.g
• NODE ptrN
• ptrN(NODE)malloc(sizeof(NODE))

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Stack in a linked list

• Using structure
• Typedef struct _stackLL
• int data
• struct _stackLL next
• STACK_LL
• Stack can be created same as linked list
• Declare a head pointer
• STACK_LL stackHead

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Stack in a linked list create

• Every newly created stack should contain no item
• So
• stackHead NULL
• Or using function
• createLLstack(stackHead)
• Function
• Void createLLstack(STACK_LL s)
• s NULL

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Stack in a linked list isempty

• In linked list we can push how many item we want
  but still need to check the emptiness of the
  stack for pop operation.
• Is it empty function
• int isempty(STACK_LL s)
• if(s NULL)
• retrun 1
• else
• return 0

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Stack in a linked list push

• To add a new item into stack
• No need to check either the stack is full or not
• Push function
• void push(STACK_LL s, int item)
• STACK_LL newNode
• newNode (STACK_LL)malloc(sizeof(STACK_LL)
  
• newNode-gtdata item
• newNode-gtnext s
• s newNode

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Stack in a linked list pop

• To get/remove an item from stack
• Check if the stack is not empty then proceed with
  pop operation
• pop function
• int pop(STACK_LL s)
• STACK_LL delNode
• int data
• delNode s
• s delNode-gtnext
• data delNode-gtdata
• free(delNode) //delete(delNode)
• return data