Data Structures using C++

  #include< iostream.h > 
  #include< conio.h > 
  #include< process.h > 
  // Creating a NODE Structure 
  struct node 
  { 
     int data; // data 
     struct node *next; // link to next node and previous node 
  }; 
  // Creating a class LIST 
  class list 
  { 
     struct node *start; 
     public: 
       void create(); // to create a list 
       void show(); // show 
       void merge(list,list); // Merge two list's 
  }; 
  // Main function 
  int main() 
  { 
     clrscr(); 
     list l1,l2,l3; 
     cout<<"Enter the First List in ascending order."; 
     l1.create(); // to create a first list 
     cout<<"Enter the Second List in ascending order."; 
     l2.create(); // to create a second list 
     cout<<"The first list is"; 
     l1.show(); 
     cout<<"The second list is"; 
     l2.show(); 
     l3.merge(l1,l2); 
     l3.show(); 
     getch(); 
     return (0); 
  } 
  // Functions 
  // Creating a new node 
  void list::create() 
  { 
     struct node *nxt_node,*pre_node; 
     int value,no,i; 
     start=nxt_node=pre_node=NULL; 
     cout<<"How many nodes : "; 
     cin>>no; 
     cout<<"Enter "<< no <<" Elements: "; 
     for(i=1;i<=no;i++) 
     { 
       cin>>value; 
       nxt_node=new node; 
       nxt_node->data=value; 
       nxt_node->next=NULL; 
       if(start==NULL) 
          start=nxt_node; 
       else 
          pre_node->next=nxt_node; 
         pre_node=nxt_node; 
     } 
     cout<<"The list is created!"; 
  } 
  // Displaying LIST 
  void list::show() 
  { 
     struct node *ptr=start; 
     cout<<"The List is "; 
     while(ptr!=NULL) 
     { 
       cout<< ptr->data<<" -> "; 
       ptr=ptr->next; 
     } 
     cout<<" "; 
  } 
  void list::merge(list l1,list l2) 
  { 
     struct node *nxt_node,*pre_node,*pptr,*qptr; 
     int dat; 
     pptr=l1.start; 
     qptr=l2.start; 
     start=nxt_node=pre_node=NULL; 
     while(pptr!=NULL && qptr!=NULL) 
     { 
       if(pptr->data<=qptr->data) 
       { 
          dat=pptr->data; 
          pptr=pptr->next; 
       } 
       else 
       { 
          dat=qptr->data; 
          qptr=qptr->next; 
       } 
       nxt_node=new node; 
       nxt_node->data=dat; 
       nxt_node->next=NULL; 
       if(start==NULL) 
          start=nxt_node; 
       else 
          pre_node->next=nxt_node; 
         pre_node=nxt_node; 
     } 
     if(pptr==NULL) 
     { 
       while(qptr!=NULL) 
       { 
          nxt_node=new node; 
          nxt_node->data=qptr->data; 
          nxt_node->next=NULL; 
          if(start==NULL) 
            start=nxt_node; 
          else 
            pre_node->next=nxt_node; 
          pre_node=nxt_node; 
          qptr=qptr->next; 
       } 
     } 
     else if(qptr==NULL) 
     { 
       while(pptr!=NULL) 
       { 
          nxt_node=new node; 
          nxt_node->data=pptr->data; 
          nxt_node->next=NULL; 
          if(start==NULL) 
            start=nxt_node; 
          else 
            pre_node->next=nxt_node; 
          pre_node=nxt_node; 
          pptr=pptr->next; 
       } 
     } 
     cout<<"The lists are merged."; 
     return; 
  }