// Write a program to implement union and intersection of two doubly linked lists.

#include <stdio.h>
#include <stdlib.h>

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

typedef struct node *NODE;

NODE getnode() {
    NODE x;
    x = (NODE)malloc(sizeof(struct node));
    if(x == NULL) {
        printf("Out of memory\n");
        exit(0);
    }
    return x;
}

void insert_rear(NODE *head, int item) {
    NODE temp, cur;
    temp = getnode();
    temp->data = item;
    temp->next = NULL;
    if(*head == NULL) {
        temp->prev = NULL;
        *head = temp;
        return;
    }
    cur = *head;
    while(cur->next != NULL)
        cur = cur->next;
    cur->next = temp;
    temp->prev = cur;
}

NODE union_lists(NODE head1, NODE head2) {
    NODE result = NULL;
    NODE temp = head1;
    while(temp != NULL) {
        insert_rear(&result, temp->data);
        temp = temp->next;
    }
    temp = head2;
    while(temp != NULL) {
        NODE cur = result;
        int found = 0;
        while(cur != NULL) {
            if(cur->data == temp->data) {
                found = 1;
                break;
            }
            cur = cur->next;
        }
        if(!found)
            insert_rear(&result, temp->data);
        temp = temp->next;
    }
    return result;
}

NODE intersection_lists(NODE head1, NODE head2) {
    NODE result = NULL;
    NODE temp = head1;
    while(temp != NULL) {
        NODE cur = head2;
        while(cur != NULL) {
            if(temp->data == cur->data) {
                insert_rear(&result, temp->data);
                break;
            }
            cur = cur->next;
        }
        temp = temp->next;
    }
    return result;
}

void display(NODE head) {
    NODE temp = head;
    while(temp != NULL) {
        printf("%d ", temp->data);
        temp = temp->next;
    }
    printf("\n");
}