C Program For LINKED LIST IMPLEMENTATION (ALL BASIC OPERATIONS)

Program By- Jayant Purohit

  

     /* PROGRAM IMPLEMENTATION OF SINGLE LINKED LIST */

  #include"stdio.h"
  #define NULL 0
  /* STRUCTURE CONTANING A DATA PART AND A LINK PART */

   struct node
 {
   int data;
   struct node *next;
 }*p;

 /*THIS FUNCTION DELETES A NODE */

void delnode(int num)
 {
     struct node *temp, *m;
temp=p;
      while(temp!=NULL)
    {
       if(temp->data==num)
       {
       if(temp==p)
       {
          p=temp->next;
          free(temp);
          return;
       }
       else
     {
       m->next=temp->next;
       free(temp);
       return;
     }
      }else
    {
       m=temp;
      temp= temp->next;
    }

}
    printf(" ELEMENT %d NOT FOUND ", num);
}

// To add NEW NODE at Last Node
void append( int num )
 {
     struct node *temp,*r;

       temp= (struct node *)malloc(sizeof(struct node));
       temp->data=num;
       r=(struct node *)p;

      if (p == NULL) /* IF LIST IS EMPTY CREATE FIRST NODE */
     {
    p=temp;
     p->next =NULL;
     }
  else
     {        /* GO TO LAST AND ADD*/

         while( r->next != NULL)
       r=r->next;
       r->next =temp;
       r=temp;
       r->next=NULL;
     }
  }/* ADD A NEW NODE AT BEGINNING  */

   void addbeg( int num )
   {
   struct node *temp;
    temp=(struct node *)malloc(sizeof(struct node));
    temp->data=num;

    if ( p== NULL)
       {
      p=temp;
      p->next=NULL;
       }

   else
      {
      temp->next=p;
      p=temp;
      }
   }


 /*  ADD A NEW NODE AFTER A SPECIFIED NO OF NODES */

void addafter(int num, int loc)
  {
     int i;
     struct node *temp,*t,*r;
     r=p;       /* here r stores the first location */
      if(loc > count()+1 || loc <= 0)
   {
     printf(" insertion is not possible : ");
        return;
   }
    if (loc == 1)/* if list is null then add at beginning */
     {
       addbeg(num);
       return;
     }
      else
 {
       for(i=1;i<loc;i++)
      {
         t=r;   /* t will be holding previous value */
         r=r->next;
      }
     temp=(struct node *)malloc(sizeof(struct node));
     temp->data=num;
     t->next=temp;
     t=temp;
     t->next=r;
    return;
       }
}

/* THIS FUNCTION DISPLAYS THE CONTENTS OF THE LINKED LIST */

void display(struct node *r)
  {
      r=p;
      if(r==NULL)
     {
       printf("NO ELEMENT IN THE LIST :");
       return;
     }
       /* traverse the entire linked list */
       while(r!=NULL)
    {
      printf(" -> %d ",r->data);
      r=r->next;
    }
     printf("");
  }
//THIS FUNCTION COUNTS THE NUMBER OF ELEMENTS IN THE LIST
 count()
 {
   struct node *n;
   int c=0;
   n=p;
    while(n!=NULL)
   {
     n=n->next;
     c++;
   }
  return(c);
 }
//THIS FUNCTION REVERSES A LINKED LIST
void reverse(struct node *q)
{
   struct node *m, *n,*l,*s;
   m=q;
   n=NULL;
  while(m!=NULL)
 {
   s=n;
   n=m;
  m=m->next;
  n->next=s;
 }
   p=n;
}


/* THIS IS THE MAIN PROGRAM  */

  main()
 {
    int i;
   p=NULL;
   clrscr();
   while(1) /* this is an indefinite loop */
 {                                                   //TO CREATE A MENU FOR DISPLAY..
    printf("\n 1.INSERT A NUMBER AT BEGINNING;");
    printf("\n 2.INSERT A NUMBER AT LAST:");
    printf("\n 3.INSERT A NUMBER AT A PARTICULAR LOCATION INlIST:");
    printf("\n 4.PRINT THE ELEMENTS IN THE LIST :");
    printf("\n 5.PRINT THE NUMBER OF ELEMENTS IN THE LIST");
    printf("\n 6.DELETE A NODE IN THE LINKED LIST:");
    printf("\n 7.REVERSE A LINKED LIST :");
    printf("\n 8.GET OUT OF LINKED LIST (BYEE BYEE):");
    printf("\n PLEASE, ENTER THE NUMBER:");
    scanf("%d",&i); /* ENTER A VALUE FOR SWITCH  */

      switch(i)
    {
     case 1:
      {
    int num;
    printf(" PLEASE ENTER THE NUMBER :-");
    scanf("%d",&num);
    addbeg(num);
    break;
      }
      case 2:
       {
     int num;
     printf(" PLEASE ENTER THE NUMBER :-");
     scanf("%d",&num);
     append(num);
     break;
       }

   case 3:
     {
      int num, loc,k;
      printf(" PLEASE ENTER THE NUMBER :-");
      scanf("%d",&num);
      printf("PLEASE ENTER THE LOCATION NUMBER :-");
      scanf("%d",&loc);
      addafter(num,loc);
      break;
    }  case 4:
      {
     struct node *n;
     printf("THE  ELEMENTS IN THE LIST ARE :");
     display(n);
     break;
      }

      case 5:
   {
      struct node *n;
      display(n);
      printf(" TOTAL NO OF ELEMENTS IN THE LSIT ARE %d",count());
      break;
   } case 6:
    {
        int    num;
      printf(" PLEASE ENTER A NUMBER FROM THE LIST :");
      scanf("%d",&num);
      delnode(num);
     break;
    }
   case 7:
    {
      reverse(p);
    display(p);
    break;
    }
  case 8:
 {
  exit();
 }
    }/* end if switch */
 }/* end of while */
}/* end of main
 */