UNIT 4: Linked List Programs demonstrated in class. Tojo Mathew Asst. Professor CSE Dept., NIE Mysuru.

Transcription

1 UNIT 4: Linked List Programs demonstrated in class. Tojo Mathew Asst. Professor CSE Dept., NIE Mysuru. 1

2 Table of Contents 1. Array Implementation of Linked List Queue using Array Implementation of Linked List Linked list implementation with basic operations Linked list implementation with a getnode( ) function Linked List based implementation of queue Linked list implementation of queue with local front & rear pointer Linked list implementation of stack with local pointer to the stack and double pointer Stack with local pointer & typedef for node pointer Stack using Circular Linked list Circular Queue using Circular Linked list Doubly Linked List...43

3 1. Array Implementation of Linked List. // Array Implementation of Linked List. #include<stdio.h> #include<stdlib.h> #define NUMNODES 100 struct nodetype int info; int next; ; struct nodetype node[numnodes]; int avail = -1; int list = -1; // Initialization of available nodes' list (free pool of nodes) void initavaillist() avail = 0; int i; for(i=avail; i<numnodes-1;i++) node[i].next = i + 1; node[numnodes-1].next = -1; // Marks end of avail list // return the index of a free node in the array int getnode() int p; if(avail == -1) printf("overflow\n"); return -1; p = avail; avail = node[avail].next; return p; // Freeing & adding the node to avail list void freenode(int p)

4 node[p].next = avail; avail = p; void insertafter(int p, int x) int q; if(p == -1) printf("void insertion\n"); q = getnode(); node[q].info = x; node[q].next = node[p].next; node[p].next = q; void delafter(int p, int *px) int q; if( (p==-1) (node[p].next == -1)) printf("void deletion\n"); q = node[p].next; *px = node[q].info; node[p].next = node[q].next; freenode(q); void insertbegin(int x) int p = getnode(); if(p!= -1) if(list ==-1) // first node node[p].next = -1; node[p].next = list;

5 node[p].info = x; list = p; int deletebegin() if(list == -1) printf("list empty\n"); return -1000; int p = list; int x = node[p].info; list = node[list].next; freenode(p); return x; void display() int p = list; printf("the List:"); while(p!= -1) printf("node[%d] = %d\t", p,node[p].info ); p = node[p].next; printf("\n"); int main() int x; initavaillist(); printf("insertbegin(10)\n"); insertbegin(10); display(); printf("insertbegin(20)\n"); insertbegin(20); display(); printf("insertbegin(30)\n"); insertbegin(30);

6 display(); printf("deletebegin()\n"); deletebegin(); display(); printf("insertbegin(40)\n"); insertbegin(40); display(); printf("insertafter(1,50)\n"); insertafter(1,50); display(); printf("delafter(1,&x)\n"); delafter(1,&x); display(); printf("\ndeleted %d",x); return 0;

7 2. Queue using Array Implementation of Linked List #include<stdio.h> #include<stdlib.h> #define NUMNODES 100 struct queue // stores index of first and last element of queue int front; int rear; ; struct nodetype int info; int next; ; struct nodetype node[numnodes]; // global queue container int avail = -1; // Initialising the available list with all nodes of the array void initavaillist() avail = 0; int i; for(i=avail; i<numnodes-1;i++) node[i].next = i + 1; node[numnodes-1].next = -1; // Marks end of AvailList // return the index of first free node in avail list int getnode() int p; if(avail == -1) printf("overflow\n");

8 return -1; p = avail; avail = node[avail].next; return p; // Add the node to avail list void freenode(int p) node[p].next = avail; avail = p; void insert(struct queue *pq, int x) // Insert at rear of queue int p = getnode(); node[p].info = x; node[p].next = -1; if(pq->rear == -1) // Check if Queue is empty pq->front = p; node[pq->rear].next = p; pq->rear = p; int empty(struct queue *pq) return ((pq->front == -1)?1:0); int delete(struct queue *pq) // delete from front of queue int p,x; if(empty(pq)) printf("queue Underflow\n"); return -1; p = pq->front; x = node[p].info;

9 pq->front = node[p].next; if(pq->front == -1) pq->rear = -1; freenode(p); return x; void display(struct queue *pq) int p = pq->front; printf("the Queue:"); while(p!= -1) printf("%d ", node[p].info ); p = node[p].next; printf("\n"); int main() struct queue q; // global q front & rear markers q.front = -1; q.rear = -1; initavaillist(); printf("insert(10)\n"); insert(&q,10); display(&q); printf("insert(20)\n"); insert(&q,20); display(&q); printf("insert(30)\n"); insert(&q,30); display(&q); printf("delete()\n"); delete(&q);

10 display(&q); return 0;

11 3. Linked list implementation with basic operations. #include<stdio.h> #include<stdlib.h> // node definition struct node int data; struct node *next; ; struct node *list = NULL; // list is global to starting of the list void insert_at_start(int newdata); // Insert new node at start of the list. void delete_first_node(); // delete first node of list void insert_at_end(int newdata); // Insert new node at end of list void delete_last_node(); // delete last node of list int delete_element(int elem); // delete node with given element. void insert_after(int existingdata, int newdata); // Insert new node after given element value void insert_at_start(int newdata) // Creation of new node struct node *temp; temp=(struct node *)malloc(sizeof(struct node)); temp->next = NULL; // Store data temp->data = newdata; if (list== NULL) printf("first node\n"); list=temp; list->next=null; temp->next=list; list=temp; void delete_first_node() struct node *temp; temp=list; if(list!= NULL)

12 list = list->next; free(temp); printf("list is already empty\n"); // Element not found void insert_at_end(int num) // Create new node struct node *cur; if(list == NULL) insert_at_start(num); cur = list; // Novigate to end of the list while(cur->next!= NULL) cur=cur->next; // Create new node struct node *temp; temp=(struct node *)malloc(sizeof(struct node)); temp->next = NULL; // Insert temp->data=num; cur->next =temp; temp->next = NULL; void delete_last_node() struct node *prev = NULL,*cur; cur=list; if(list!= NULL) // Navigate to last node while(cur->next!= NULL) prev = cur; cur = cur->next; if(prev == NULL) printf("only one node in list. Deleting it to result in empty list");

13 free(cur); list = NULL; free(cur); prev->next = NULL; printf("list is already empty\n"); int delete_element(int num) struct node *cur, *prev; cur = list; // cur points to first node initially. while(cur!=null) if(cur->data==num) if(cur==list) list=cur->next; free(cur); return 1; prev->next=cur->next; free(cur); return 1; // Success prev=cur; cur= cur->next; return 0; // Element not found void insert_after(int val, int newdata) struct node *cur; cur = list; while(cur!=null) if(cur->data == val)

14 cur=cur->next; if(cur!=null) // Create new node struct node *temp; temp=(struct node *)malloc(sizeof(struct node)); temp->next = NULL; // insert temp->data=newdata; temp->next = cur->next; cur->next = temp; printf("element not found!!"); void display() struct node* temp=list; if(temp==null) printf("list is Empty\n"); printf("the List is : "); while(temp!=null) printf("%d-->",temp->data); temp=temp->next; printf("null\n"); // Count number of nodes in the list int count() struct node *temp; int c=0; temp=list; while(temp!=null) temp=temp->next; c++; return c;

15 int main() int i,num,elem; list=null; while(1) printf("\nlist Operations\n"); printf("===============\n"); printf("1.insert At Start\t"); printf("2.insert At End\t\t"); printf("3.insert_after given element\n"); printf("4.delete At Start\t"); printf("5.delete At End\t\t"); printf("6.delete Given element\n"); printf("7.display\t\t"); printf("8.exit\n\n"); printf("enter your choice : "); if(scanf("%d",&i)<=0) printf("enter only an Integer\n"); exit(0); switch(i) case 1: printf("enter the number to insert : "); scanf("%d",&num); insert_at_start(num); display(); case 2: printf("enter the number to insert : "); scanf("%d",&num); insert_at_end(num); display(); case 3: printf("enter the number to insert :"); scanf("%d",&num); printf("enter the existing elem :"); scanf("%d",&elem); insert_after(elem,num); display(); case 4: delete_first_node(num); display(); case 5: delete_last_node(num);

16 display(); case 6: if(list==null) printf("list is Empty\n"); printf("enter the number to delete : "); scanf("%d",&num); if(delete_element(num)) printf("%d deleted successfully\n",num); printf("%d not found in the list\n",num); display(); case 7: display(); case 8: return 0; default: printf("invalid option\n"); return 0;

17 4. Linked list implementation with a getnode( ) function. // Linked list implementation with a getnode function. #include<stdio.h> #include<stdlib.h> // node definition struct node int data; struct node *next; ; struct node *list = NULL; // list is global to starting of the list struct node* getnode(); // Creates a new empty node and return the address void insert_at_start(int newdata); // Insert new node at start of the list. void insert_at_end(int newdata); // Insert new node at end of list void insert_after(int existingdata, int newdata); // Insert new node after given element value int delete_element(int elem); // delete node with given element. void delete_first_node(); // delete first node of list void delete_last_node(); // delete last node of list struct node* search(int x); // Search for an element & return the pointer of the node struct node* getnode() struct node *temp; temp=(struct node *)malloc(sizeof(struct node)); temp->next = NULL; return temp; void insert_at_start(int newdata) // Creation on new node struct node *temp; temp = getnode(); // Store data temp->data=newdata; if (list== NULL) printf("first node\n"); list=temp; list->next=null;

18 temp->next=list; list=temp; void delete_first_node() struct node *temp; temp=list; if(list!= NULL) list = list->next; free(temp); printf("list is already empty\n"); // Element not found void insert_at_end(int num) // Create new node struct node *cur; if(list == NULL) insert_at_start(num); cur = list; // Novigate to end of the list while(cur->next!= NULL) cur=cur->next; // Creation on new node struct node *temp; temp = getnode(); // Insert temp->data=num; cur->next =temp; temp->next = NULL; void delete_last_node() struct node *prev = NULL,*cur; cur=list;

19 if(list!= NULL) // Navigate to last node while(cur->next!= NULL) prev = cur; cur = cur->next; if(prev == NULL) printf("only one node in list. Deleting it to result in empty list.\n"); free(cur); list = NULL; free(cur); prev->next = NULL; printf("list is already empty\n"); int delete_element(int num) struct node *cur, *prev = NULL; cur=list; while(cur!=null) if(cur->data==num) if(cur==list) // deleting first node itself. So list need to be updated list=cur->next; free(cur); return 1; prev->next=cur->next; free(cur); return 1; // Success prev=cur; cur= cur->next;

20 return 0; // Element not found void insert_after(int val, int newdata) // place struct node *cur; cur = list; while(cur!=null) if(cur->data == val) cur=cur->next; if(cur!=null) // Create new node // Creation on new node struct node *temp; temp = getnode(); // insert temp->data=newdata; temp->next = cur->next; cur->next = temp; printf("element not found!!"); struct node* search(int x) struct node *cur; cur = list; while(cur!=null) if(cur->data == x) cur=cur->next; return cur;

21 void display() struct node* temp=list; if(temp==null) printf("list is Empty\n"); printf("the List is : "); while(temp!=null) printf("%d-->",temp->data); temp=temp->next; printf("null\n"); // Count number of nodes in the list int count() struct node *temp; int c=0; temp=list; while(temp!=null) temp=temp->next; c++; return c; int main() int i,num,elem; list=null; while(1) printf("\nlist Operations\n"); printf("===============\n"); printf("1.insert At Start\t"); printf("2.insert At End\t\t"); printf("3.insert_after given element\n"); printf("4.delete At Start\t"); printf("5.delete At End\t\t"); printf("6.delete Given element\n"); printf("7.search\t\t"); printf("8.display\t\t"); printf("9.exit\n\n"); printf("enter your choice : "); if(scanf("%d",&i)<=0) printf("enter only an Integer\n");

22 exit(0); switch(i) case 1: printf("enter the number to insert : "); scanf("%d",&num); insert_at_start(num); display(); case 2: printf("enter the number to insert : "); scanf("%d",&num); insert_at_end(num); display(); case 3: printf("enter the number to insert :"); scanf("%d",&num); printf("enter the existing elem :"); scanf("%d",&elem); insert_after(elem,num); display(); case 4: delete_first_node(num); display(); case 5: delete_last_node(num); display(); case 6: if(list==null) printf("list is Empty\n"); printf("enter the number to delete : "); scanf("%d",&num); if(delete_element(num)) printf("%d deleted successfully\n",num); printf("%d not found in the list\n",num); display(); case 7: printf("enter the element to search :"); scanf("%d",&elem); struct node *res = search(elem); if(res == NULL)

23 printf("element not found in list\n"); printf("element found in list at node %p\n",res); case 8: display(); case 9: return 0; default: printf("invalid option\n"); return 0;

24 5. Linked List based implementation of queue. #include<stdio.h> #include<stdlib.h> // node definition struct node int data; struct node *next; ; struct node *front = NULL; // Pointer to front of Q. NULL for empty Q struct node *rear = NULL; // Pointer to rear of Q struct node* getnode(); // Creates a new empty node and return the address void freenode(struct node* n); struct node* getnode() struct node *temp; temp=(struct node *)malloc(sizeof(struct node)); temp->next = NULL; return temp; void freenode(struct node* n) free(n); //Insert at rear end of Q void insert(int num) // Create new node // Creation & init of new node struct node *temp; temp = getnode(); temp->data=num; temp->next = NULL; if(rear == NULL) front = rear = temp; rear->next = temp; rear =temp;

25 // remove from front end Q void delete() struct node *temp; temp = front; if(front!= NULL) front = front->next; freenode(temp); if(front == NULL) rear = NULL; // List is empty printf("list is already empty\n"); // Element not found void display() struct node* temp=front; if(temp==null) printf("list is Empty\n"); printf("the List is : "); while(temp!=null) printf("%d-->",temp->data); temp=temp->next; printf("null\n"); int main() int choice,num; front = NULL; while(1) printf("\nlist Operations\n");

26 printf("===============\n"); printf("1.insert At End\t\t"); printf("2.delete At Start\t"); printf("3.display\t\t"); printf("4.exit\n\n"); printf("enter your choice : "); if(scanf("%d",&choice)<=0) printf("enter only an Integer\n"); exit(0); switch(choice) case 1: printf("enter the number to insert : "); scanf("%d",&num); insert(num); display(); case 2: delete(num); display(); case 3: display(); case 4: return 0; default: printf("invalid option\n"); return 0;

27 6. Linked list implementation of queue with local front & rear pointer. #include<stdio.h> #include<stdlib.h> // node definition struct node int data; struct node *next; ; struct Queue struct node *front; // list is global to starting of the list struct node *rear; ; struct node* getnode(); // Creates a new empty node and return the address void freenode(struct node* n); void insert(struct Queue* q, int newdata); // Insert new node at end of list void delete(struct Queue* q); // delete last node of list struct node* getnode() struct node *temp; temp=(struct node *)malloc(sizeof(struct node)); temp->next = NULL; return temp; void freenode(struct node* n) free(n); void insert(struct Queue* q, int num) // Create new node // Creation & init of new node struct node *temp; temp = getnode(); temp->data=num; temp->next = NULL;

28 if(q->rear == NULL) q->front = q->rear = temp; q->rear->next = temp; q->rear =temp; void delete(struct Queue* q) struct node *temp; temp = q->front; if(q->front!= NULL) q->front = q->front->next; freenode(temp); if(q->front == NULL) q->rear = NULL; // List is empty printf("list is already empty\n"); // Element not found void display(struct Queue *q) struct node* temp=q->front; if(temp==null) printf("list is Empty\n"); printf("the List is : "); while(temp!=null) printf("%d-->",temp->data); temp=temp->next; printf("null\n");

29 int main() int choice,num; struct Queue q; q.front = NULL; q.rear = NULL; while(1) printf("\nlist Operations\n"); printf("===============\n"); printf("1.insert At End\t\t"); printf("2.delete At Start\t"); printf("3.display\t\t"); printf("4.exit\n\n"); printf("enter your choice : "); if(scanf("%d",&choice)<=0) printf("enter only an Integer\n"); exit(0); switch(choice) case 1: printf("enter the number to insert : "); scanf("%d",&num); insert(&q,num); display(&q); case 2: delete(&q); display(&q); case 3: display(&q); case 4: return 0; default: printf("invalid option\n"); return 0;

30 7. Linked list implementation of stack with local pointer to the stack and double pointer. #include<stdio.h> #include<stdlib.h> // node definition struct node int data; struct node *next; ; struct node *getnode(); // Creates a new empty node and return the address void freenode(struct node *n); void push(struct node **st, int newdata); // Insert new node at start void pop(struct node **st); // delete from start struct node *getnode() struct node *temp; temp=(struct node *)malloc(sizeof(struct node)); temp->next = NULL; return temp; void freenode(struct node *n) free(n); void push(struct node **st, int newdata) // Create new node // Creation & init of new node struct node *temp; temp = getnode(); temp->data= newdata; temp->next = NULL; if(*st == NULL) // First push printf("first Push\n"); *st = temp;

31 printf("subsequent Push\n"); temp->next = *st ; *st = temp; void pop(struct node **st) struct node *temp; temp = *st; if(*st!= NULL) *st = (*st)->next; freenode(temp); printf("stack is already empty\n"); // Element not found void display(struct node *st) struct node *temp=st; if(temp==null) printf("stack is Empty\n"); printf("the Stack is : "); while(temp!=null) printf("%d-->",temp->data); temp=temp->next; printf("null\n"); int main() int choice,num; struct node *st = NULL; while(1)

32 printf("\nstack Operations\n"); printf("===============\n"); printf("1.push\t\t"); printf("2.pop\t"); printf("3.display\t\t"); printf("4.exit\n\n"); printf("enter your choice : "); if(scanf("%d",&choice)<=0) printf("enter only an Integer\n"); exit(0); switch(choice) case 1: printf("enter the number to push : "); scanf("%d",&num); push(&st,num); display(st); case 2: pop(&st); display(st); case 3: display(st); case 4: return 0; default: printf("invalid option\n"); return 0;

33 8. Stack with local pointer & typedef for node pointer. #include<stdio.h> #include<stdlib.h> // node definition struct node int data; struct node * next; ; typedef struct node * NODEPTR; NODEPTR getnode(); // Creates a new empty node and return the address void freenode(nodeptr n); void push(nodeptr *st, int newdata); // Insert new node at start void pop(nodeptr *st); // delete from start NODEPTR getnode() NODEPTR temp; temp=(nodeptr )malloc(sizeof(struct node)); temp->next = NULL; return temp; void freenode(nodeptr n) free(n); void push(nodeptr *st, int newdata) // Create new node // Creation & init of new node NODEPTR temp; temp = getnode(); temp->data=newdata; temp->next = NULL; if(*st == NULL) // First push printf("first Push\n"); *st = temp;

34 printf("subseq Push\n"); temp->next = *st ; *st = temp; void pop(nodeptr *st) NODEPTR temp; temp = *st; if(*st!= NULL) *st = (*st)->next; freenode(temp); printf("stack is already empty\n"); void display(nodeptr st) NODEPTR temp=st; if(temp==null) printf("stack is Empty\n"); printf("the Stack is : "); while(temp!=null) printf("%d-->",temp->data); temp=temp->next; printf("null\n"); int main() int choice,num; NODEPTR st = NULL; while(1)

35 printf("\nstack Operations\n"); printf("===============\n"); printf("1.push\t\t"); printf("2.pop\t"); printf("3.display\t\t"); printf("4.exit\n\n"); printf("enter your choice : "); if(scanf("%d",&choice)<=0) printf("enter only an Integer\n"); exit(0); switch(choice) case 1: printf("enter the number to push : "); scanf("%d",&num); push(&st,num); display(st); case 2: pop(&st); display(st); case 3: display(st); case 4: return 0; default: printf("invalid option\n"); return 0;

36 9. Stack using Circular Linked list. #include<stdio.h> #include<stdlib.h> // node definition struct node int data; struct node * next; ; typedef struct node * NODEPTR; NODEPTR getnode(); // Creates a new empty node and return the address void freenode(nodeptr n); void push(nodeptr *st, int newdata); // Insert new node at start int pop(nodeptr *st); // delete from start NODEPTR getnode() NODEPTR temp; temp=(nodeptr )malloc(sizeof(struct node)); temp->next = NULL; return temp; void freenode(nodeptr n) free(n); int empty(nodeptr *pstack) return (*pstack == NULL)?1:0; void push(nodeptr *pstack, int newdata) // Create new node // Creation & init of new node NODEPTR p; p = getnode(); p->data=newdata; p->next = NULL; if(*pstack == NULL) // First push

37 printf("first Push\n"); *pstack = p; p->next = *pstack; printf("subseq Push\n"); p->next = (*pstack)->next ; (*pstack)->next = p; int pop(nodeptr *pstack) int x; NODEPTR p; if(empty(pstack)== 1) printf("stack is already empty\n"); return -1000; p = (*pstack)->next; x = p->data; if(p == *pstack) // Only one node in stack *pstack = NULL; (*pstack)->next = p->next; freenode(p); return x; void display(nodeptr st) if(st==null) printf("stack is Empty\n"); NODEPTR temp=st->next;

38 printf("the Stack is :\n"); do printf("%d-->",temp->data); temp=temp->next; while(temp!=st->next); printf("start\n"); int main() int choice,num; NODEPTR st = NULL; while(1) printf("\nstack Operations\n"); printf("===============\n"); printf("1.push\t\t"); printf("2.pop\t"); printf("3.display\t\t"); printf("4.exit\n\n"); printf("enter your choice : "); if(scanf("%d",&choice)<=0) printf("enter only an Integer\n"); exit(0); switch(choice) case 1: printf("enter the number to push : "); scanf("%d",&num); push(&st,num); display(st); case 2: printf("removed element %d\n",pop(&st)); display(st); case 3: display(st); case 4: return 0; default: printf("invalid option\n"); return 0;

39

40 10. Circular Queue using Circular Linked list. #include<stdio.h> #include<stdlib.h> // node definition struct node int data; struct node * next; ; typedef struct node * NODEPTR; NODEPTR getnode(); // Creates a new empty node and return the address void freenode(nodeptr n); void insert(nodeptr *st, int newdata); // Insert new node at start int delete(nodeptr *st); // delete from start NODEPTR getnode() NODEPTR temp; temp=(nodeptr )malloc(sizeof(struct node)); temp->next = NULL; return temp; void freenode(nodeptr n) free(n); int empty(nodeptr *cq) return (*cq == NULL)?1:0; void insert(nodeptr *cq, int newdata) // Create new node // Creation & init of new node NODEPTR p; p = getnode(); p->data=newdata; p->next = NULL; if(*cq == NULL) // First insert

41 printf("first insert\n"); *cq = p; p->next = *cq; printf("subseq insert\n"); p->next = (*cq)->next ; (*cq)->next = p; *cq = p; int delete(nodeptr *cq) int x; NODEPTR p; if(empty(cq)== 1) printf("stack is already empty\n"); return -1000; p = (*cq)->next; x = p->data; if(p == *cq) // Only one node in stack *cq = NULL; (*cq)->next = p->next; freenode(p); return x; void display(nodeptr st) if(st==null) printf("queue is Empty\n"); NODEPTR temp=st->next;

42 printf("the Queue is :\n"); do printf("%d-->",temp->data); temp=temp->next; while(temp!=st->next); printf("start\n"); int main() int choice,num; NODEPTR st = NULL; while(1) printf("\nstack Operations\n"); printf("===============\n"); printf("1.insert\t\t"); printf("2.delete\t"); printf("3.display\t\t"); printf("4.exit\n\n"); printf("enter your choice : "); if(scanf("%d",&choice)<=0) printf("enter only an Integer\n"); exit(0); switch(choice) case 1: printf("enter the number to insert : "); scanf("%d",&num); insert(&st,num); display(st); case 2: printf("removed element %d\n",delete(&st)); display(st); case 3: display(st); case 4: return 0; default: printf("invalid option\n"); return 0;

43 11. Doubly Linked List // A C program to demonstrate insertion & deletion in DLL #include <stdio.h> #include <stdlib.h> // A linked list node struct Node int data; struct Node *right; struct Node *left; ; /* Given a reference (pointer to pointer) to the head of a list and an int, inserts a new node on the front of the list. */ void insert_begin(struct Node** head, int new_data) /* 1. allocate node */ struct Node* new_node = (struct Node*) malloc(sizeof(struct Node)); /* 2. put in the data */ new_node->data = new_data; /* 3. Make right of new node as head and leftious as NULL */ new_node->right = (*head); new_node->left = NULL; /* 4. change left of head node to new node */ if((*head)!= NULL) (*head)->left = new_node ; /* 5. move the head to point to the new node */ (*head) = new_node; /* Given a node as left_node, insert a new node after the given node */ void insertafter(struct Node* left_node, int new_data) /*1. check if the given left_node is NULL */ if (left_node == NULL) printf("the given leftious node cannot be NULL"); /* 2. allocate new node */ struct Node* new_node =(struct Node*) malloc(sizeof(struct Node)); /* 3. put in the data */ new_node->data = new_data; /* 4. Make right of new node as right of left_node */ new_node->right = left_node->right;

44 /* 5. Make the right of left_node as new_node */ left_node->right = new_node; /* 6. Make left_node as leftious of new_node */ new_node->left = left_node; /* 7. Change leftious of new_node's right node */ if (new_node->right!= NULL) new_node->right->left = new_node; /* Given a reference (pointer to pointer) to the head of a DLL and an int, insert_ends a new node at the end */ void insert_end(struct Node** head, int new_data) /* 1. allocate node */ struct Node* new_node = (struct Node*) malloc(sizeof(struct Node)); struct Node *last = *head; /* used in step 5*/ /* 2. put in the data */ new_node->data = new_data; /* 3. This new node is going to be the last node, so make right of it as NULL*/ new_node->right = NULL; /* 4. If the Linked List is empty, then make the new node as head */ if (*head == NULL) new_node->left = NULL; *head = new_node; /* 5. Else traverse till the last node */ while (last->right!= NULL) last = last->right; /* 6. Change the right of last node */ last->right = new_node; /* 7. Make last node as leftious of new node */ new_node->left = last; // This function prints contents of linked list starting from the given node void printlist(struct Node *node) printf("\ntraversal in forward direction \n");

45 printf("null <==> "); while (node!= NULL) printf(" %d <==>", node->data); node = node->right; printf("null\n"); /* Function to delete a node in a Doubly Linked List. head_ref --> pointer to head node pointer. del --> pointer to node to be deleted. */ void deletenode(struct Node **head_ref, struct Node *del) /* base case */ if(*head_ref == NULL del == NULL) /* If node to be deleted is head node */ if(*head_ref == del) *head_ref = del->right; /* Change right only if node to be deleted is NOT the last node */ if(del->right!= NULL) del->right->left = del->left; /* Change left only if node to be deleted is NOT the first node */ if(del->left!= NULL) del->left->right = del->right; /* Finally, free the memory occupied by del*/ free(del); /* Driver program to test above functions*/ int main() /* Start with the empty list */ struct Node* head = NULL; // Insert 6. So linked list becomes 6->NULL insert_end(&head, 6); // Insert 7 at the beginning. So linked list becomes 7->6->NULL insert_begin(&head, 7); // Insert 1 at the beginning. So linked list becomes 1->7->6->NULL insert_begin(&head, 1); // Insert 4 at the end. So linked list becomes 1->7->6->4->NULL insert_end(&head, 4);

46 // Insert 8, after 7. So linked list becomes 1->7->8->6->4->NULL insertafter(head->right, 8); printf("created DLL is: "); printlist(head); deletenode(&head, head->right->right); /*delete middle node*/ /* Modified linked list will be NULL<-8->NULL */ printf("\n Modified Linked list "); printlist(head); getchar(); return 0;