Data Structure Lab Programs -Program to reverse a linked list .

Practical # 9

 

 

/* Program to reverse a linked list */

 

#include<stdio.h>

#include<conio.h>

#include<alloc.h>

 

/* structure containing a data part and link part */

struct node

{

                int data;

                struct node *link;

};

 

void addatbeg(struct node **,int);

void reverse(struct node **);

void display(struct node *);

int count(struct node *);

 

void main()

{

struct node *p;

p=NULL;

 

addatbeg(&p,7);

addatbeg(&p,43);

addatbeg(&p,17);

addatbeg(&p,3);

addatbeg(&p,23);

addatbeg(&p,5);

 

clrscr();

display(p);

printf("\nNo. of element in the linked list=%d",count(p));

 

reverse(&p);

display(p);

printf("\nNo. of elements in the linked list=%d",count(p));

}

/* adds a new node at the beginning of the linked list */

void addatbeg(struct node **q,int num)

{

struct node *temp;

/*add new node*/

temp=(struct node*)malloc(sizeof(struct node));

temp->data=num;

temp->link=*q;

*q=temp;

}

void reverse(struct node **x)

{

struct node *q,*r,*s;

 

q=*x;

r=NULL;

/* traverse the entire linked list */

while(q!=NULL)

{

s=r;

r=q;

q=q->link;

r->link=s;

}

*x=r;

}

 

/*display the contents of the linked list */

void display(struct node *q)

{

printf("\n");

 

/*traverse the entire linked list */

while(q!=NULL)

{

printf("%d",q->data);

q=q->link;

}

}

/* counts the number of nodes present in the ll:*/

int count(struct node *q)

{

int c=0;

/* traverse the entire ll*/

while(q!=NULL)

{

q=q->link;

c++;

}

return c;

}

 

 

Output :-

 

 

5 23 3 17 43 7

 

No. of element in the linked list=6

 

 

 

7 43 17 3 23 5

 

No. of elements in the linked list=6