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Linked Lists
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Structure for Linked List:
We have already used a simple node definition:
struct Node
{
int data;Node *link;
};
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Insert at end
Inserts an element at the end of the list
void insertend(int x)
{ Node *temp = head;
while (temp -> link != NULL)
temp = temp->link;
Node *newer = new Node;
newer->data = x;
newer->link = NULL;
temp->link = newer;
} 10 12 14 head
newer
16
temp
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Delete a Node after a Node
Delete an element after the specific node
int delafter(Node *temp)
{ Node *temp1 = temp->next;
int x = temp->data;
temp = temp1->link;
delete temp1;
return x;
}
10 12 14 head 16
temp
temp1
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Assignment
Merge two lists. Delete all occurrences of a number from the
list.
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Stacks As Singly Linked List
We can implement a stack with a singly linked list
The head pointer points to the first node.
Both insertion and deletion are done from head side.
We had already done.Stacks
head
nodes
elements
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Queue with a Singly Linked List
We can implement a queue with a singly linked list
The front element is stored at the first node
The rear element is stored at the last node
Stacks
7
front
rear
nodes
elements
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struct Queue{
int info;
Queue *link;
};
Queue *front, *rear;rear = front = NULL;
Queue Operations
frontrear
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bool empty()
{
if ( front==NULL)
return TRUE;
else
return FALSE;
}
Queue Operations
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int remove()
{
if (empty()){
cout link;
if (front== NULL)
rear = NULL;delete temp;return x;
}
Queue Operations
front
rear
temp642 8
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Void insert(int x)
{
Queue *temp = new Queue;temp->info=x;temp->link =
NULL;
if (rear== NULL)front = temp;
elserear->link = temp;
rear = temp;}
Queue Operations
front
rear
temp
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We can not reach any of the nodethat precede a node p.
If a list is traversed the externalpointer is needed to be
preserved tobe able to refer the list again.
Solution is to use a Circular List
Shortcomings of linked linear list
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Circular List
Circular List: The tail of the list points back to the head
There is no NULL pointer to end the list.62 84
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Circular List
There is no first and last node in circular list so we establish
a first, last
node by convention First Node
Last Node Last
An external pointer is used to point to last node.62 84
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Stacks as a Circular List
Let last be the pointer pointing to the last node in the
stackand first node be considered as top of the stack.
Implementation of Stackstruct Node{
int info;Node *link;
};Node *last;last = NULL;
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bool empty()
{
if (last == NULL)
return TRUE;else
return FALSE:
}
Stack Operations
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void push(int x)
{
Node * temp = new Node;
temp->info = x;
if (last == NULL)last = temp;
else
temp->link = last->link;
}
last->link = temp;
}
PUSH
642
last
1
temp
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int pop()
{
int x; Node *temp;
if (empty()) {coutlink;x = temp->info;
if (temp == last)
last = NULL;
else
last->link = temp->link;
delete temp;return x;
}
POP
642
last
1
temp
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void insert(int x)
{
int x; Node *temp= new node;
temp->info = x;
if (empty())last = temp;
else
temp->link = last->link;
last->link = temp->info;
last = temp;
}
Queue As Circular List
642
last
1
temp
8
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void delafter(Node *p)
{
int x; Node *temp;
if (p==NULL || p==p->link)
{coutlink;
x = p->info;
p->link = temp->next;
delete temp;}
DELAFTER()
642
last
1
temp
8
p
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read n;
read(name);
while (name != END)
{insert name on the circular list;
read(name);
}
while (there is more than one node on the list)
{count through n-1 nodes on the list;
print the name in the nth node;
delete nth node
}Print the name of the only node on the list
Josephus Problem
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List can not be traversed backward.
A node can not be deleted from it,
given only a pointer to that node.Solution is to use a Doubly
LinkedList
Shortcomings of circular list
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Doubly-Linked Lists
Each node contains two pointers, one to its successorand one to
its predecessor.
Doubly linked list can be linear or circular.
88NULL 42 109 NULL
head
left info right
88 42 109
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Same basic functions operate on list
Insertleft()
Insertright()
Delete()
deleteleft()
deleteright()
We have
left(right(p)) =p = right(left(p))
Doubly-Linked Lists
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Doubly link list can be implemented using lists.
Each node contains left, right pointers and info
part.
struct node{
int info;
node *left, *right;};
Implementation of Doubly-
Linked Lists
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Delete
int Delete(Node *p)
{
Node *q, *r; int x;
if (p==NULL){ cout info;
q = p->left;
r = p->right;
q->right = r;
r->left = q;
delete p;
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Insertright
void insertright(Node *p, int x)
{
Node *q, *r;
if (p==NULL)
{ cout info = x;
r = p->right;
r->left = q;
q->right = r;
q->left = p;
p->right = q;
}
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Insert on head side
void insert(Node *head, int x)
{
Node *q, *r;
r = head;q = new node;
q->info = x;
q->right = r;
q->left = NULL;r->left = q;
head = q;
}
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Deletion on head side
int insert(Node *head)
{
Node *q, *r;
int x;r = head;
q= r->right;
q->left = NULL;
r->right = NULL;x = r->info;
head = q;
delete r;
}
