Stacks and Queues with Linked List.pdf

DATA STRUCTURES
Stacks & Queues
using
Linked List
Dr G.Kalyani
Department of Information Technology
VR Siddhartha engineering College

Topics
• Stacks using linked List
• Queues using Linked List

• Instead of using array, we can also use linked list to
implement stack.
• Linked list allocates the memory dynamically.
• In linked list implementation of stack, the nodes are
maintained non-contiguously in the memory.
• Each node contains a pointer to its immediate successor
node in the stack.
• Stack is said to be overflown if the space left in the memory
heap is not enough to create a node.
• The top most node in the stack always contains null in its
address field.
Linked list implementation of stack

Linked list implementation of stack

Algorithmpush ()
{
int val;
Allocatememoryto newnode;
if(newnode == NULL)
{
Writenot able to push the element;
}
else
{
read val;
newnode ->data = val;
newnode ->next= TOS;
TOS= newnode ;
writeItempushed;
}
}
PUSH Operation

POP Operation
Algorithm POP()
{
int item;
struct node *temp;
if (TOS == NULL)
{
write Underflow;
}
else
{
item = TOS->val;
temp = TOS;
TOS = TOS->next;
free(temp);
write Itempopped;
}
}

Algorithm display()
{
struct node *ptr;
temp=TOS;
if(TOS == NULL)
{
write Stack is empty;
}
else
{
write Printing Stack elements;
while(temp!=NULL)
{
write temp->val;
temp = temp->next;
}
}
}
Traversing or Display

Linked List Implementation of Queues
• In a linked queue, each node of the queue consists of two parts
i.e. data part and the link part.
• Each element of the queue points to its immediate next element
in the memory.
• In the linked queue, there are two pointers maintained in the
memory i.e. front pointer and rear pointer.
• The front pointer contains the address of the starting element of
the queue while the rear pointer contains the address of the last
element of the queue.
• Insertion and deletions are performed at rear and front end
respectively.
• If front and rear both are NULL, it indicates that the queue is
empty.

Linked List Implementation of Queues

Insert Operation
AlgorithmInsert_Q()
{
Struct node *newnode;
Allocatememoryto newnode;
if(newnode == NULL)
{
writememorynot allocated
return;
}
else
{
newnode -> data = item;
if(front == NULL and rear==NULL)
{
front = newnode;
rear = newnode;
front -> next= NULL;
rear -> next = NULL;
}
else
{
rear -> next = newnode;
rear = newnode;
rear->next= NULL;
}
}
}

Algorithm delete ()
{
struct node *ptr;
if(front == NULL and rear==NULL)
{
write UNDERFLOW;
return;
}
else
{
ptr = front;
front = front -> next;
free(ptr);
}
}
Delete Operation

Traversing or Display
Algorithm display()
{
struct node *temp;
temp = front;
if(front == NULL)
{
Write Empty queue;
}
else
{
Write Queue Elements:;
while(temp != NULL)
{
Write temp -> data;
temp = temp -> next;
}
}
}

Stacks and Queues with Linked List.pdf

Stacks and Queues with Linked List.pdf

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