# Week 3 Honors Assignment - Doubly Linked List

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```/* Modify the singly linked list to be a doubly linked list.
Now write a routine that removes all duplicate data in the doubly linked list.
The data will be integers generated at random from [0,49].
Initially have a list of 200 elements.  */
#include <stdlib.h>
#include <stdio.h>
#include <time.h> // This give us the time for generating random variables.

#define ARRAY_SIZE 200
#define RAND_MAX 2147483647  // Define the max number in the rand() function.
#define RANDOM_NUMBER rand() % 50 // Generate a random number from [0,49].
// Function for filling the array with random integers.
#define FILL for (int j = 0; j < ARRAY_SIZE; j++) data[j] = RANDOM_NUMBER

// Defining each list data node with a struct.
typedef struct list {
int data;
struct list *next;
struct list *prev;
} list;

// Funtion for creating the list.
list *create_list(int d)
{
list *head = malloc(sizeof(list));
}

// Function for adding a new element to the list.
list *add_to_front(int d, list *h)
{
list *head = create_list(d);
}

// Function for removing a node from the list.
void remove_from_list(list *node)
{
if (node == NULL) return;
if (node->prev == NULL)
{
node->next->prev = NULL;
free(node);
return;
}
if (node->next == NULL) {
node->prev->next = NULL;
free(node);
return;
}
node->next->prev = node->prev;
node->prev->next = node->next;
free(node);
}

// Function for removing all duplicates values from the list.
void remove_duplicates(list *h)
{
while (h != NULL)
{
list *n = h->next;
while(n != NULL)
{
list *temp = n->next;
if (h->data == n->data) remove_from_list(n);
n = temp;
}
h = h->next;
}
}

// Function for creating a list from an array.
list *array_to_list(int d[], int size)
{
list *head = create_list(d[0]);
for (int i = 1; i < size; i++)
{
}
}

// Function for printing the list in rows of 5.
void print_list(list *h)
{
int i = 0;
while (h != NULL)
{
printf("%d\t", h->data);
h = h->next;
i++;
if (i % 5 == 0) printf("\n");
}
printf("\n");
}

// Function for freeing the memory used for the linked list creation.
void free_list(list *h)
{
while (h != NULL)
{
list *temp = h;
h = h->next;
free(temp);
}
}

// Here we define the program to create a list, remove duplicates, and print it.
int main(void)
{
// Seeding the random generator with the time.
srand(time(NULL));
// Defining the array.
int data[ARRAY_SIZE];
// Filling the array with the random integers.
FILL;
// Creating a list from the array.
list *new_list = array_to_list(data, ARRAY_SIZE);
// Printing the old list.
printf("Old list:\n");
print_list(new_list);
// Remove duplicates from the list.
remove_duplicates(new_list);
// Printing the new list.
printf("New list:\n");
print_list(new_list);
// Freeing the memory.
free_list(new_list);
return 0;
}```