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Basic Questions on linked list: in c

Note : im always considering head node for simplification:

Advantages of head node:

1.if im reversing a linked list I need to change first node of linked list so if I have head node no need to change head change nodes after head node then every time my first node is head only

2.we can maintain some data about linked list like number nodes in list 

Applications :

Inserting into linked list ,and displaying nodes and reversing linked list

Codes :

#include<stdio.h>

#include<conio.h>

#include<malloc.h>

// structure definition

struct node

{

      int data;

      struct node *next;

};

void insert(struct node *,int );//inserting at end

void display(struct node *);//displaying all nodes

void insertstart(struct node *);//inserting at start

void reverselist(struct node *);//reversing list

//main function

void main()

{

     struct node *head=NULL;

      int i=1,j,choice;

      struct node *temp1,*temp2,*prev;

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

      head->data=0;

      head->next=NULL;

   while(i)

     {

      printf("\n enter 1 to insert elements");

      printf("\n enter 2 display");

      printf("\n enter 3 to insert at start”);
      printf(""\n enter 4 to revrse linked list");

      printf("\n enter 0 to exit");

      scanf("%d",&i);

   switch(i)

   {

           

      case 1:

            printf("enter element to insert");

            scanf("%d",&j);

            insert(head,j);

            break;

     

      case 2:

            display(head);   

            break;

           

      case 3:

            printf("enter element to insert");

            scanf("%d",&j);

            insertstart(head,j);

             break;

      case 4:

            reverselist(head);

            break;

     

     

       }//end ofswitch   

     }//end of while

}

//Inserting in linked list:

void insert(struct node *head,int i)

{

      struct node *temp,*q;

      if(head->next==NULL)

      {

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

      temp->data=i;

      temp->next=NULL;

      head->next=temp;

      }

           

      else

      {

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

            temp->data=i;

            temp->next=NULL;

            q=head;

            while(q->next!=NULL)

            q=q->next;

            q->next=temp;

           

       }

}//end of insert

//displaying  :

  void display(struct node *head)

    {

      struct node *temp;

      temp=head->next;

       while(temp!=NULL)

       {

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

            temp=temp->next;

        }

      }

//reversing linked list:

void reverselist(struct node *head)

{

      struct node *current,*prev,*next;

      prev=NULL;

      current=head->next;

          while(current!=NULL)

           {

            next=current->next;

            current->next=prev;

            prev=current;

            current=next;

            }

            head->next=prev;

}//end of reverse

//inserting at start

void insertstart(struct node *head,int i)

{

      struct node *temp,*t;

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

    temp->data=i;

      t=head->next;

      head->next=temp;

      temp->next=t;

}