PRESENTATION OF STACK AND QUEUE

STACK

STACK:

• A stack is a data linear data structure in which addition of new element or deletion of an existing element always takes place at the same end. This end is called as top of the stack • When an item is added to a stack, the operation is called as push • when an item is removed from the stack, the operation is called as pop• stack is also called as last–in-first-out (LIFO).

PUSH POP

ALGORITHM FOR STACK : (push)

PUSH (stack[MAX_SIZE],item) : This algorithm an item at the top of the stack[MAX_SIZE].

STEP-1: Initialize Set top = -1

STEP-2: Repeat step-3 to 5 until top<MAXSIZE-1

STEP-3: Read item

STEP-4: Set top=top+1

STEP-5:Set stack[top]=item

STEP-6:Print “stack overflow”

C function for push operation on stack : int stack[5] , top = -1; void push( ) { int item; if (top<=4) { printf(“\n Enter the number”); scanf(“%d”, &item); top=top+1; stack [top] = item; } else { printf(“\n stack overflow”); } }

Algorithm for stack: (pop)

POP(stack[MAXSIZE],item) : This algorithm deletes an item from the top of the stack STEP-1: Repeat steps 2 to 4 until top>=0

STEP-2: Set item = stack [top]

STEP-3: Set top = top - 1

STEP-4: Print No. deleted is , item

STEP-5: Print stack underflow

C function for pop operation on stack int stack [5],top; void pop ( ) { int item; if (top>=0) { item = stack [top]; top=top-1; printf("\n Number deleted is = %d ", item); } else { printf("\n stack is empty"); }}

objects: a finite ordered list with zero or more elements.

functions: for all stack € Stack , item € element, maxStackSize € positive integer . Stack CreateS(maxStackSize)::=

create an empty stack whose maximum size is maxStackSize

Boolean IsFull( stack, maxStackSize )::=if(number of elements in stack==maxStackSize)

return TRUE else return FALSE

ADT Stack is

Stack Push( stack, item)::= if(IsFull(stack))stack Full

else insert item into top of stack and return.

Boolean IsEmpty(stack)::=if(stack==CreateS( maxStackSize )return TRUEelse return FALSE

Element Pop(stack)::= if(IsEmpty(stack))return else remove and return the element at

the top of the stack.

Direct applicationsPage-visited history in a Web browserUndo sequence in a text editorSaving local variables when one function calls another, and this one calls another, and so on.

Indirect applicationsAuxiliary data structure for algorithmsComponent of other data structures

Application of stack

QUEUE

QUEUE :

• Queue is a linear data structure that permits the insertion of new element at one end and deletion of an element at the other end.•The end at which the deletion of an element takes place is called as front and the end at Which insertion of new element can take place is called as rear.• Queue is also called as first-in-first-out (FIFO).

ENQUEUE

BACK FRONT

DEQUEUE

Algorithm for insertion of queue :

QINSERT (Queue[MAXSIZE],item) : This algorithm inserts an item at the rear of queue [MAXSIZE]

STEP-1: Initialisation. set front = -1 set rear = -1

STEP-2: Repeat steps 3 to 5 until rear<MAXSIZE -1

STEP-3: Read item

STEP-4: If front = = -1 then

front = 0 rear = 0 Else rear = rear + 1

STEP-5: Set Queue [Rear] = item

STEP-6: Print, Queue overflow

C function for insertion of Queue :

int queue [5], front = -1, rear = -1 ;Void queue ( ){ int item ; if (rear < 4){ printf(“\n Enter the number ”); scanf(“%d ” & item ); if (front = = -1 ) { front = 0 ; rear = 0; }

else { rear = rear + 1 ; } queue [rear] = item ; } else { printf (“\n Queue is full”); } }

Algorithm for deletion of queue :

QDELETE (queue [MAXSIZE] , item ) : This algorithm deletes an item at the front of the queue [MAXSIZE].

STEP-1: Repeat steps 2 to 4 until front >= 0

STEP-2: Set item = queue [front]

STEP-3: If front = = rear set front = -1 set rear = -1 else front = front + 1

STEP-4: Print “ Number deleted is ”, item

STEP-5: print “ Queue is empty ”

C function for deletion operation in queue :

int queue [5] , front , rear ; void delete ( ){ int item ; If ( front ! = -1) { item = queue [front]; if (front = = rear ) { front = -1; rear = -1 ; }

front = front +1 ; } printf (“\n Number deleted is = %d “, item ); } else { printf( “ Queue is empty”);}}

ADT for Queue

ADT Queue isobjects: a finite ordered list with zero or more elements.functions: for all queue € Queue,item € element ,maxQueueSize € positive integer

Queue CreateQ(maxQueueSize)::= create an empty queue whose maximum size is maxQueueSizeBoolean IsFullQ(queue,maxQueueSize)::= if(number of elements in queue==maxQueueSize) return TRUE else return FALSE

Queue AddQ(queue,item)::= if(IsFullQ(queue))queueFull else insert item at rear of queue and return queueBoolean IsEmptyQ(queue)::= if(queue==CreateQ(maxQueueSize)) return TRUE else return FALSE

Element DeleteQ(queue)::= if(IsEmptyQ(queue)) return else remove and return the item at front of queue.

1)Serving requests of a single shared resource (printer, disk, CPU),transferring data asynchronously (data not necessarily received at same rate as sent) between two processes (IO buffers), e.g., pipes, file IO, sockets. 2) Call center phone systems will use a queue to hold people in line until a service representative is free.

APPLICATION OF QUEUE :

3) When a resource is shared among multiple consumers. Examples include CPU scheduling, Disk Scheduling.

4) Buffers on MP3 players and portable CD players, iPod playlist. Playlist for jukebox – add songs to the end, play from the front of the list.

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