Combine Two Doubly Linked Lists

				
					#include<stdio.h>

#include<stdlib.h>

struct node {
  int info;
  struct node * lptr, * rptr;
}* l, * r, * l1, * r1;
void doubins(int);
void doubins1(int);
void display();
void display1();
void merge();
int chk;
void main() {
  int ch, x;
  l = NULL;
  r = NULL;
  l1 = NULL;
  r1 = NULL;
  do {
    printf("\n\n [1] Create First Doubly Linked List");
    printf("\n [2] Create Second Doubly Linked List");
    printf("\n [3] Merge both list");
    printf("\n [4] Exit");
    printf("\n\n\tEnter Choice: ");
    scanf("%d", & ch);
    switch (ch) {
    case 1:
      printf("\n\tEnter Element: ");
      scanf("%d", & x);
      doubins(x);
      display();
      break;
    case 2:
      printf("\n\tEnter Element: ");
      scanf("%d", & x);
      doubins1(x);
      display1();
      break;
    case 3:
      merge();
      display();
      break;
    case 4:
      exit(0);
    default:
      printf("\n\tInvalid Choice.\n\tTry Again.");
    }
  } while (ch != 3);
}
void doubins(int x) {
  struct node * New, * temp;
  int sc;
  New = (struct node * ) malloc(sizeof(struct node));
  New -> info = x;
  if (l == NULL) {
    New -> lptr = NULL;
    New -> rptr = NULL;
    l = New;
    r = New;
    return;
  }
  if (x <= l -> info) {
    New -> lptr = NULL;
    New -> rptr = l;
    l -> lptr = New;
    l = New;
    return;
  }
  temp = l;
  while (temp -> rptr != NULL && temp -> info < x) {
    temp = temp -> rptr;
  }
  if (temp -> info < x) {
    New -> rptr = NULL;
    New -> lptr = r;
    r -> rptr = New;
    r = New;
    return;
  }
  New -> lptr = temp -> lptr;
  New -> rptr = temp;
  temp -> lptr = New;
  New -> lptr -> rptr = New;
}
void doubins1(int x) {
  struct node * New, * temp;
  int sc;
  New = (struct node * ) malloc(sizeof(struct node));
  New -> info = x;
  if (l1 == NULL) {
    New -> lptr = NULL;
    New -> rptr = NULL;
    l1 = New;
    r1 = New;
    return;
  }
  if (x <= l1 -> info) {
    New -> lptr = NULL;
    New -> rptr = l1;
    l1 -> lptr = New;
    l1 = New;
    return;
  }
  temp = l1;
  while (temp -> rptr != NULL && temp -> info < x) {
    temp = temp -> rptr;
  }
  if (temp -> info < x) {
    New -> rptr = NULL;
    New -> lptr = r1;
    r1 -> rptr = New;
    r1 = New;
    return;
  }
  New -> lptr = temp -> lptr;
  New -> rptr = temp;
  temp -> lptr = New;
  New -> lptr -> rptr = New;
}
void display() {
  struct node * temp;
  if (l == NULL)
    printf("\n\n\tDoubly Linked List is Empty.");
  else {
    printf("\n\nDoubly Linked List:\n\n\n");
    printf("-----------------------------\n");
    printf("l = %u\n\n", l);
    printf("-----------------------------\n");
    temp = l;
    while (temp != NULL) {
      printf("[%u|%u|%d|%u]->", temp, temp -> lptr, temp -> info, temp -> rptr);
      temp = temp -> rptr;
    }
    printf("NULL");
    printf("\n\nr= %u", r);
  }
}
void display1() {
  struct node * temp;
  if (l1 == NULL)
    printf("\n\tDoubly Linked List is Empty.");
  else {
    printf("\n\nDoubly Linked List:\n\n\n");
    printf("l1 = %u\n\n", l1);
    temp = l1;
    while (temp != NULL) {
      printf("[%u|%u|%d|%u]->", temp, temp -> lptr, temp -> info, temp -> rptr);
      temp = temp -> rptr;
    }
    printf("NULL");
    printf("\n\nr1= %u", r1);
  }
}
void merge() {
  r -> rptr = l1;
  l1 -> lptr = r;
}